Concepts of Genetics 11th Edition By Klug, Cummings, Spencer & Palladino Test Bank

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Concepts of Genetics 11th Edition By Klug, Cummings, Spencer & Palladino Test Bank

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COMPLETE TEST BANK WITH ANSWERS
 Concepts of Genetics 11th Edition By Klug, Cummings, Spencer & Palladino Test Bank
SAMPLE QUESTIONS

 

Chapter 2   Mitosis and Meiosis

 

1) If a typical somatic cell has 64 chromosomes, how many chromosomes are expected in each gamete of that organism?

  1. A) 8
  2. B) 16
  3. C) 32
  4. D) 64
  5. E) 128

Answer:  C

Section:  2.4

 

2) In an organism with 52 chromosomes, how many bivalents would be expected to form during meiosis?

  1. A) 13
  2. B) 26
  3. C) 52
  4. D) 104
  5. E) 208

Answer:  B

Section:  2.4

 

3) In a healthy male, how many sperm cells would be expected to be formed from (a) 400 primary spermatocytes? (b) 400 secondary spermatocytes?

  1. A) (a) 800; (b) 800
  2. B) (a) 1600; (b) 1600
  3. C) (a) 1600; (b) 800
  4. D) (a) 400; (b) 400
  5. E) (a) 100; (b) 800

Answer:  C

Section:  2.5

 

4) In a healthy female, how many secondary oocytes would be expected to form from 100 primary oocytes? How many first polar bodies would be expected from 100 primary oocytes?

  1. A) 200; 50
  2. B) 100; 50
  3. C) 200; 300
  4. D) 100; 100
  5. E) 50; 50

Answer:  D

Section:  2.5

 

5) The ant, Myrmecia pilosula, is found in Australia and is named bulldog because of its aggressive behavior. It is particularly interesting because it carries all its genetic information in a single pair of chromosomes. In other words, 2n = 2. (Males are haploid and have just one chromosome.) Which of the following figures would most likely represent a correct configuration of chromosomes in a metaphase I cell of a female?

  1. A)
  2. B)
  3. C)

 

  1. D)

 

  1. E)

 

Answer:  A

Section:  2.4

 

6) For the purposes of this question, assume that a G1 somatic cell nucleus in a female Myrmecia pilosula contains 2 picograms of DNA. How much DNA would be expected in a metaphase I cell of a female?

  1. A) 16 picograms
  2. B) 32 picograms
  3. C) 8 picograms
  4. D) 4 picograms
  5. E) Not enough information is provided to answer the question.

Answer:  D

Section:  2.4

7) Myrmecia pilosula actually consists of several virtually identical, closely related species, with females having chromosome numbers of 18, 20, 32, 48, 60, 62, and 64. Assume one crossed a female of species (A) with 32 chromosomes and a male of species (B) with 9 chromosomes (males are haploid, and each gamete contains the n complement). How many chromosomes would one expect in the body (somatic) cells of the female offspring?

  1. A) 4.5
  2. B) 9
  3. C) 25
  4. D) 32
  5. E) 41

Answer:  C

Section:  2.4

 

8) What is the outcome of synapsis, a significant event in meiosis?

  1. A) side-by-side alignment of nonhomologous chromosomes
  2. B) dyad formation
  3. C) monad movement to opposite poles
  4. D) side-by-side alignment of homologous chromosomes
  5. E) chiasma segregation

Answer:  D

Section:  2.4

 

9) During interphase of the cell cycle, ________.

  1. A) DNA recombines
  2. B) sister chromatids move to opposite poles
  3. C) the nuclear membrane disappears
  4. D) RNA replicates
  5. E) DNA content essentially doubles

Answer:  E

Section:  2.3

 

10) Assume that the somatic cells of a male contain one pair of homologous chromosomes (e.g., AaAb), and an additional chromosome without a homolog (e.g., W). What chromosomal combinations would be expected in the meiotic products (spermatids) of a single primary spermatocyte? (There may be more than one answer.)

Answer:  AaW, AaW, Ab, Ab  or  Aa, Aa, AbW, AbW

Section:  2.4

 

11) Trisomy 21 or Down syndrome occurs when there is a normal diploid chromosomal complement of 46 chromosomes plus one (extra) chromosome #21. Such individuals therefore have 47 chromosomes. Assume that a mating occurs between a female with Down syndrome and a normal 46-chromosome male. What proportion of the offspring would be expected to have Down syndrome? Justify your answer.

Answer:  One-half of the offspring would be expected to have Down syndrome because of 2 1 segregation of chromosome #21 at anaphase I.

Section:  2.4

12) Normal diploid somatic (body) cells of the mosquito Culex pipiens contain six chromosomes. Assign the symbols AmAp, BmBp, and CmCp to the three homologous chromosomal pairs. The m superscript indicates that the homolog is maternally derived; the p indicates a paternally derived homolog. Assume that in the genus Culex, the sex chromosomes are morphologically identical.

 

(a) For each of the cell types given below, draw and label (with reference to the symbols defined above) an expected chromosomal configuration.

 

Mitotic metaphase

Metaphase of meiosis I

Metaphase of meiosis II

 

(b) The stage at which sister chromatids go to opposite poles immediately follows which of the stages listed in (a)?

 

(c) Assuming that all nuclear DNA is restricted to chromosomes and that the amount of nuclear DNA essentially doubles during the S phase of interphase, how much nuclear DNA would be present in each cell listed above? Note: Assume that the G1 nucleus of a mosquito cell contains 3.0 10-12 grams of DNA.

 

(d) Given that the sex of Culex is determined by alleles of one gene, males heterozygous, Mm, and females homozygous, mm, illustrate a labeled chromosomal configuration (involving the symbols AmAp, BmBp, and CmCp and the M locus) in a primary spermatocyte at metaphase. Assume that the M locus is on the AmAp chromosome and that crossing over has not occurred between the M locus and the centromere.

 

Answer:

(a)

 

(b) Metaphase of meiosis II and mitotic metaphase

 

(c) 6, 6, 3

 

 

(d)

 

Section:  2.5

 

 

13) Drosophila melanogaster, the fruit fly, has a 2n chromosome number of 8. Assume that you are microscopically examining the mitotic and meiotic cells of this organism. You note that in the female, two chromosomal pairs are metacentric and that two pairs are acrocentric.

 

(a) Draw the chromosomal configurations as you would expect to see them at the stages listed:

 

Mitotic metaphase                               First polar body (metaphase)

Primary oocyte (metaphase)                Ootid(G1)

Secondary oocyte (metaphase)

 

(b) Given that the above-mentioned cells are from individuals heterozygous for two independently segregating, autosomal loci, plum eyes and curled wings, place appropriate symbols (of your designation) on chromosomes in the drawings you made in part (a) above. Assume no crossing over, and there may be more than one correct answer in some cases.

 

(c) Assuming that a somatic G2 nucleus from the individuals mentioned above contains about 8.0 picograms of DNA, how much nuclear DNA would you expect in each of the cells mentioned above?

Answer:

(a,b)

 

(c) 8, 8, 4, 4, 2

Section:  2.5

14) Down syndrome, or trisomy 21, in humans is caused by an extra copy of the relatively small, acrocentric chromosome #21. Including only chromosome #21, the X chromosome (medium in size and somewhat metacentric), and the Y chromosome (small and acrocentric), draw one possible array of chromosomes in the four sperm cells produced by the complete meiosis of one primary spermatocyte. For the purposes of this question, assume that males with Down syndrome produce normal ratios of sperm cells. (More than one answer is possible.)

Answer:

 

Section:  2.2, 2.5

 

15) Assume that an organism has a diploid chromosome number of six. Two chromosomal pairs are telocentric, and the other pair is metacentric. Assume that the sex chromosomes are morphologically identical. Draw chromosomes as you would expect them to appear at the following stages:

 

Primary oocyte (metaphase)

Secondary spermatocyte (metaphase)

First polar body (metaphase)

Answer:

 

Section:  2.2, 2.5

 

16) The accompanying sketch depicts a cell from an organism in which 2n = 2 and each chromosome is metacentric.

 

(a) Circle the correct stage for the cell in this sketch:

anaphase of mitosis

anaphase of meiosis I

anaphase of meiosis II

telophase of mitosis

 

 

 

(b) Given that each G1 nucleus from this organism contains 16 picograms of DNA, how many picograms of chromosomal DNA would you expect in the cell shown above?

Answer:

(a) anaphase of meiosis II

(b) 16

Section:  2.2, 2.4

 

17) There is about as much nuclear DNA in a primary spermatocyte as in ________ (how many) spermatids?

Answer:  4

Section:  2.5

 

18) You may have heard through various media of an animal alleged to be the hybrid of a rabbit and a cat. Given that the cat (Felis domesticus) has a diploid chromosome number of 38 and a rabbit (Oryctolagus cuniculus) has a diploid chromosome number of 44, what would be the expected chromosome number in the somatic tissues of this alleged hybrid?

Answer:  41

Section:  2.3

 

19) The horse (Equus caballus) has 32 pairs of chromosomes, whereas the donkey (Equus asinus) has 31 pairs of chromosomes. How many chromosomes would be expected in the somatic tissue of a mule?

Answer:  63

Section:  2.4

 

20) Name two evolutionarily significant benefits of meiosis that are not present in mitosis.

Answer:  reshuffling of homologous chromosomes and crossing over

Section:  2.4

 

 

21) How many haploid sets of chromosomes are present in a diploid individual cell with a chromosome number of 46? 32?

Answer:  2; 2

Section:  2.3

22) How many haploid sets of chromosomes are present in an individual cell that is tetraploid (4n)?

Answer:  4

Section:  2.3

 

23) The nucleolus organizer (NOR) is responsible for production of what type of cell structure?

Answer:  ribosome

Section:  2.1

 

24) Regarding the mitotic cell cycle, what is meant by a checkpoint?

Answer:  A checkpoint is the portion of a cell cycle that is sensitive to a variety of conditions that impact the eventual health of the cell or individual. Such checkpoints often restrict passage to the next event in the cell cycle.

Section:  2.3

 

25) What is meant by the term chiasma?

Answer:  areas where chromatids intertwine during meiosis

Section:  2.4

 

26) List four terms used to describe the normal morphologies, with respect to arm ratio, of eukaryotic chromosomes.

Answer:  metacentric, submetacentric, acrocentric, telocentric

Section:  2.2

 

27) Name two cellular organelles, each having genetic material, that are involved in either photosynthesis or respiration.

Answer:  chloroplasts and mitochondria

Section:  2.1

 

28) Homologous chromosomes are those that can be matched by virtue of their similar structure and function within a nucleus. Which chromosomes making up a genome do not follow the same characteristics of homology?

Answer:  sex-determining chromosomes

Section:  2.2

 

29) After which meiotic stage (meiosis I or II) would one expect monads to be formed?

Answer:  meiosis II

Section:  2.4

 

 

30) List, in order of appearance, all the cell types expected to be formed during (a) spermatogenesis and (b) oogenesis.

Answer:

(a) spermatogonia, primary spermatocyte, secondary spermatocyte, spermatid, spermatozoa

(b) oogonium, primary oocyte, secondary oocyte and first polar body, ootid and second polar body

Section:  2.5

 

31) List in order of occurrence the phases of (a) mitosis and (b) prophase I of meiosis.

Answer:

(a) prophase, prometaphase, metaphase, anaphase, telophase

(b) leptonema, zygonema, pachynema, diplonema, diakinesis

Section:  2.4

32) Two terms, reductional and equational, generally refer to which stages of meiosis (I or II)?

Answer:  meiosis I and meiosis II, respectively

Section:  2.4

 

33) In which stage of the cell cycle is G0 located?

Answer:  G1

Section:  2.3

 

34) When cells withdraw from the continuous cell cycle and enter a quiescent phase, they are said to be in what stage?

Answer:  G0

Section:  2.3

 

35) The house fly, Musca domestica, has a haploid chromosome number of 6. How many chromatids should be present in a diploid, somatic, metaphase cell?

Answer:  24

Section:  2.3

 

36) A chromosome may contain one or two chromatids in different phases of the mitotic or meiotic cell cycle.

Answer:  TRUE

Section:  2.3, 2.4

 

37) If a typical G1 nucleus contains 2C (two complements) of DNA, a gamete that is haploid (n) contains 1C of DNA.

Answer:  TRUE

Section:  2.4

 

38) If a typical G1 nucleus is 2n and contains 2C (two complements) of DNA, a prophase I cell is 2n and contains 4C of DNA.

Answer:  TRUE

Section:  2.3

 

39) During meiosis, chromosome number reduction takes place in anaphase II.

Answer:  FALSE

Section:  2.4

 

40) S phase is the part of interphase when DNA duplication takes place.

Answer:  TRUE

Section:  2.3

 

41) The centromere of a chromosome separates during anaphase.

Answer:  TRUE

Section:  2.3

 

42) A bivalent at pachytene contains four chromatids.

Answer:  TRUE

Section:  2.4

43) The meiotic cell cycle involves two cell divisions but only one DNA replication.

Answer:  TRUE

Section:  2.4

 

44) An organism with a haploid number of 10 will produce 1024 combinations of chromosomes at the end of meiosis.

Answer:  TRUE

Section:  2.4

 

45) An organism with a diploid chromosome number of 46 will produce 223 combinations of chromosomes at the end of meiosis.

Answer:  TRUE

Section:  2.4

Chapter 4   Extensions of Mendelian Genetics

 

1) With incomplete dominance, a likely ratio resulting from a monohybrid cross would be ________.

  1. A) 3:3
  2. B) 1:2:2:4
  3. C) 1:2:1
  4. D) 9:3:3:1
  5. E) 3:1

Answer:  C

Section:  4.3

 

2) A situation in which there are more than two alternative forms of a given gene would be called ________.

  1. A) multiple alleles
  2. B) alternation of generations
  3. C) codominance
  4. D) incomplete dominance
  5. E) hemizygosity

Answer:  A

Section:  4.5

 

3) A condition in which one gene pair masks the expression of a nonallelic gene pair is called ________.

  1. A) codominance
  2. B) epistasis
  3. C) dominance
  4. D) recessiveness
  5. E) additive alleles

Answer:  B

Section:  4.8

 

4) Typical ratios resulting from epistatic interactions in dihybrid crosses would be ________.

  1. A) 9:3:3:1, 1:2:1
  2. B) 1:1:1:1, 1:4:6:4:1
  3. C) 9:3:4, 9:7
  4. D) 1:2:2:4:1:2:1:2:1
  5. E) 3:1, 1:1

Answer:  C

Section:  4.8

 

 

5) With which of the following would hemizygosity most likely be associated?

  1. A) codominance
  2. B) incomplete dominance
  3. C) trihybrid crosses
  4. D) X-linked inheritance
  5. E) sex-limited inheritance

Answer:  D

Section:  4.11

6) A mutation in a gene often results in a reduction of the product of that gene. The term for this type of mutation is ________.

  1. A) codominance
  2. B) incomplete dominance
  3. C) gain of function
  4. D) multiple allelism
  5. E) loss of function or null (in the case of complete loss)

Answer:  E

Section:  4.1

 

7) Because of the mechanism of sex determination, males of many species can be neither homozygous nor heterozygous. Such males are said to be ________.

  1. A) dominant
  2. B) hemizygous
  3. C) recessive
  4. D) complementary
  5. E) None of the answers listed is correct.

Answer:  B

Section:  4.11

 

8) Assume that a dihybrid cross (AaBb AaBb) is made in which the gene loci are autosomal, independently assorting, and incompletely dominant. What phenotypic ratio would you expect from such a cross? Just provide the ratio, not the phenotypes.

Answer:  1:2:1:2:4:2:1:2:1

Section:  4.3

 

9) Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Assume that two fully heterozygous plants are crossed. Give the phenotypes (with frequencies) of the offspring.

Answer:  12 (white):3 (yellow):1 (green)

Section:  4.8

 

 

10) In mice, there is a set of multiple alleles of a gene for coat color. Four of those alleles are as follows:

 

C         = full color (wild)

cch       = chinchilla

cd        = dilution

c          = albino

 

Given that the gene locus is not sex-linked and that each allele is dominant to those lower in the list, diagram the crosses indicated below and give the phenotypic ratios expected from each.

 

(a) wild (heterozygous for dilution) chinchilla (heterozygous for albino)

(b) chinchilla (heterozygous for albino) albino

Answer:

(a)        Ccd  cchc  2 full color:1 chinchilla:1 dilution

(b)        cchc  cc 1 chinchilla:1 albino

Section:  4.5

11) A mutant gene that produces brown eyes (bw) is located on chromosome #2 of Drosophila melanogaster, whereas a mutant gene producing bright red eyes, scarlet (st), is located on chromosome #3. Phenotypically, wild-type flies (with dull red eyes), whose mothers had brown eyes and whose fathers had scarlet eyes, were mated. The 800 offspring possessed the following phenotypes: wild type (dull red), white, scarlet (bright red), and brown. Most of the 800 offspring had wild-type eyes, whereas those with white eyes were the least frequent.

 

(a) Using standard symbolism, diagram the cross from the P generation (brown-eyed mothers scarlet-eyed fathers) and the F1 generation. Be certain to provide the alleles of the mutant genes.

(b) From the information presented above, how many white-eyed flies would you expect in the F2 generation?

Answer:

(a)  P     bw/bw; st+/st+               bw+/bw+; st/st

F1:  bw+/bw; st+/st               bw+/bw; st+/st

 

(b) 50

Section:  4.8

 

 

12) In the mouse, gene A allows pigmentation to be deposited in the individual coat hairs; its allele a prevents such deposition of pigment, resulting in an albino. Gene B gives agouti (wild-type fur); its allele b gives black fur.

 

(a) Diagram the cross between a doubly heterozygous agouti mouse mated with a doubly homozygous recessive white mouse.

(b) What would be the expected phenotypic ratio in the progeny?

Answer:

(a)        AaBb aabb

(b)        1 (agouti):1 (black):2 (albino)

Section:  4.8

 

13) The trait of medium-sized leaves in iris is determined by the genetic condition PP. Plants with large leaves are PP, whereas plants with small leaves are PP. A cross is made between two plants each with medium-sized leaves. If they produce 80 seedlings, what would be the expected phenotypes, and in what numbers would they be expected? What is the term for this allelic relationship?

Answer:  20 (large leaves), 40 (medium leaves), 20 (small leaves); incomplete dominance

Section:  4.4

14) The trait for medium-sized leaves in iris is determined by the genetic condition PP. Plants with large leaves are PP, whereas plants with small leaves are PP. The trait for red flowers is controlled by the genes RR, pink by RR, and white by RR. A cross is made between two plants each with medium-sized leaves and pink flowers. If they produce 320 seedlings, what would be the expected phenotypes, and in what numbers would they be expected? Assume no linkage.

Answer:

20 large, red

40 medium, red

20 small, red

40 large, pink

80 medium, pink

40 small, pink

20 large, white

40 medium, white

20 small, white

Section:  4.4

 

 

15) The following coat colors are known to be determined by alleles at one locus in horses:

 

palomino = golden coat with lighter mane and tail

cremello = almost white

chestnut = brown

 

The following table gives ratios obtained in matings of the above varieties:

 

Cross             Parents                     Offspring

 

1          cremello cremello            all cremello

2          chestnut chestnut            all chestnut

3          cremello chestnut            all palomino

4          palomino palomino         1/4 = chestnut

1/2 = palomino

1/4 = cremello

 

Assign gene symbols for the genetic control of coat color on the basis of these data.

Diagram the last two matings.

Answer:  C1C1 = cremello, C2C2 = chestnut, C1C2 = palomino

(3)        C1C1  C2C2

(4)         C1C2  C1C2

Section:  4.5

 

16) What is meant by the term epistasis? Distinguish between epistasis and dominance. Do not use examples in answering this question.

Answer:  Epistasis refers to a gene (or genes) of one pair masking the expression of a gene (or genes) at a different locus. Dominance refers to the form of expression of a gene in relation to its allele (or alleles). When an allele is dominant, the heterozygous combination is the same phenotypically as one of the homozygotes. Epistasis is a nonallelic interaction; dominance is an allelic interaction.

Section:  4.8

17) The following F2 results occur from a typical dihybrid cross:

 

purple:       A_B_         9/16

white:        aaB_         3/16

white:        A_bb         3/16

white:        aabb          1/16

 

If a double heterozygote (AaBb) is crossed with a fully recessive organism (aabb), what phenotypic ratio is expected in the offspring?

Answer:  3 (white):1 (purple)

Section:  4.8

 

 

18) Which types of ratios are likely to occur in crosses (F2) when one is dealing with two interacting, epistatic gene pairs?

Answer:  9:7, 9:3:4, 12:3:1, 15:1

Section:  4.8

 

19) Assume that a cross is made between two organisms that are both heterozygous for a gene that shows incomplete dominance. What phenotypic and genotypic ratios are expected in the offspring?

Answer:  1:2:1

Section:  4.3

 

20) Assume that a dihybrid cross is made in which the genes loci are autosomal, independently assorting, and incompletely dominant. How many different phenotypes are expected in the offspring?

Answer:  9

Section:  4.3

 

21) How many different alleles can a gene have?

Answer:  Theoretically, an extremely large number of possibilities exist. Various bases could change, giving a variety of alleles, and combinations of those changed bases could provide additional variety.

Section:  4.1

 

22) Assume that a dihybrid F2 ratio, resulting from epistasis, was 9:3:4. If a double heterozygote was crossed with the fully recessive type, what phenotypic ratio is expected among the offspring?

Answer:  1:1:2

Section:  4.8

 

23) Assume that a dihybrid F2 ratio, resulting from epistasis, was 15:1. If a double heterozygote was crossed with the fully recessive type, what phenotypic ratio is expected among the offspring?

Answer:  3:1

Section:  4.8

 

24) Name four modes of inheritance that are influenced by the sex of individuals.

Answer:  X-linked, sex-influenced, sex-limited, Y-linked

Section:  4.11, 4.12

25) The white-eye gene in Drosophila is recessive and sex-linked. Assume that a white-eyed female is mated to a wild-type male. What would be the phenotypes of the offspring?

Answer:  females wild type, males white eyed

Section:  4.11

 

 

26) Two forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their first son will have hemophilia?

Answer:  1/2

Section:  4.11

 

27) Two forms of hemophilia are determined by genes on the X chromosome in humans. Assume that a phenotypically normal woman whose father had hemophilia is married to a normal man. What is the probability that their first daughter will have hemophilia?

Answer:  0

Section:  4.11

 

28) State a significant difference between X-linked and sex-influenced inheritance.

Answer:  In X-linked inheritance, the gene in question is on the X chromosome; in sex-influenced inheritance, the gene is autosomal.

Section:  4.11, 4.12

 

29) Pattern baldness is determined by a single autosomal gene pair. When females are homozygous for this gene pair, can they show pattern baldness?

Answer:  Yes, but the phenotype is less pronounced and is expressed later in life.

Section:  4.12

 

30) Provide an example of sex-influenced inheritance.

Answer:  pattern baldness in humans, horn formation in sheep, certain coat patterns in sheep

Section:  4.13

 

31) What distinguishes sex-limited from sex-influenced inheritance?

Answer:  In sex-limited inheritance, expression is limited to one sex; in sex-influenced inheritance, expression differs between the sexes.

Section:  4.12

 

32) Comb shape in chickens represents one of the classic examples of gene interaction. Two gene pairs interact to influence the shape of the comb. The genes for rose comb (R) and pea comb (P) together produce walnut comb. The fully homozygous recessive condition (rrpp) produces the single comb. Assume that a rose-comb chicken is crossed with a walnut-comb chicken and the following offspring are produced: 17 walnut, 16 rose, 7 pea, 6 single.

 

(a) What are the probable genotypes of the parents?

(b) Give the genotypes of each of the offspring classes.

Answer:

(a)        Rrpp RrPp

 

(b) R_Pp   (walnut)

      R_pp    (rose)

      rrPp     (pea)

      rrpp     (single)

Section:  4.8

33) Many of the color varieties of summer squash are determined by several interacting loci: AA or Aa gives white, aaBB or aaBb gives yellow, and aabb produces green. Crosses among heterozygotes give a 12:3:1 ratio. What type of gene interaction would account for these results?

Answer:  epistasis

Section:  4.8

 

34) A particular cross gives a modified dihybrid ratio of 9:7. What phenotypic ratio would you expect in a testcross of the fully heterozygous F1 crossed with the fully recessive type? Diagram the testcross using A,a,B,b as symbol sets.

Answer:  1:3   AaBb aabb > AaBb, Aabb, aaBb, aabb

Section:  4.8

 

35) The enzyme glucose-6-phosphate dehydrogenase deficiency (G6PD) is inherited as a recessive gene on the X chromosome in humans. A phenotypically normal woman (whose father had G6PD) is married to a normal man.

 

(a) What fraction of their sons would be expected to have G6PD?

(b) If the husband had G6PD, would it make a difference in your answer in part (a)?

Answer:

(a) 1/2

(b) no

Section:  4.11

 

36) A cross was made between homozygous wild-type female Drosophila and yellow-bodied male Drosophila. All of the resulting offspring were phenotypically wild type. Offspring of the F2 generation had the following phenotypes:

 

Sex                  Phenotype       Number

 

male                wild                   96

male                yellow                99

female             wild                 197

 

Based on this information:

(a) Is the mutant gene for yellow body behaving as a recessive or dominant?

(b) Is the yellow locus on an autosome or on the X-chromosome?

Answer:

(a) recessive

(b) X-chromosome

Section:  4.11

 

37) Below is a pedigree of a fairly common human hereditary trait in which the boxes represent males and the circles represent females. Shading symbolizes the abnormal phenotype.

 

Given that one gene pair is involved:

(a) Is the inheritance pattern X-linked or autosomal, recessive or dominant?

(b) Give the genotype of each individual in the pedigree. If more than one genotypic possibility exists, present all possible alternatives.

 

 

Answer:

(a) autosomal recessive

 

(b)

 

Section:  4.11

 

38) The genes for zeste eyes and forked bristles are located on the X chromosome in Drosophila melanogaster. Both genes are recessive. A cross is made between a zeste-eyed female and a forked-bristled male.

 

(a) If 200 offspring from this cross were obtained, present the expected number, sex, genotype, and phenotype in each class of the F1.

(b) If the F1 offspring were crossed to produce 800 flies of an F2 generation, present the expected number, sex, and phenotype in each class. Assume no crossing over.

Answer:

(a)        z+f/z f+      =          wild female     (100)

            z f+/Y        =          zeste male        (100)

 

(b)        z+f/z f+      =          wild female     (200)

            z f+/z f+     =          zeste female    (200)

            z+f/Y         =          forked male     (200)

            z f+/Y        =          zeste male        (200)

Section:  4.11

 

 

39) In a mating between individuals with the genotypes IAi  ii, what percentage of the offspring would be expected to have the O blood type?

Answer:  50%

Section:  4.5

40) In a mating between individuals with the genotypes IAIB  ii, what percentage of the offspring would be expected to have the O blood type?

Answer:  zero

Section:  4.5

 

41) If an X-linked disorder is lethal to the affected individual prior to the age at which one reaches reproductive maturation, the lethality will be expressed only in males. Why is this so?

Answer:  The only sources of the lethal allele in the population are heterozygous females who are carriers and do not express the disorder.

Section:  4.6, 4.11

 

42) Can females display pattern baldness?

Answer:  When females inherit the BB genotype, they can definitely express hair thinning; however, it is less pronounced than in males and occurs later in life.

Section:  4.12

 

43) Regarding the ABO blood group system in humans, if an individual is genetically IBi and yet expresses the O blood type, which genotype is it likely to have?

Answer:  hh (Bombay)

Section:  4.5, 4.8

 

44) With multiple alleles, there can be more than two genetic alternatives for a given locus.

Answer:  TRUE

Section:  4.5

 

45) With both incomplete dominance and codominance, one expects heterozygous and homozygous classes to be phenotypically identical.

Answer:  FALSE

Section:  4.3, 4.4

 

46) The ABO blood group locus in humans provides an example of epistasis.

Answer:  FALSE

Section:  4.5

 

47) Sex-limited inheritance is the same as sex-linked inheritance.

Answer:  FALSE

Section:  4.11, 4.12

 

48) A conditional mutant is one whose expression is influenced by some environmental condition.

Answer:  TRUE

Section:  4.13

49) A typical epistatic ratio is 9:3:4.

Answer:  TRUE

Section:  4.8

 

50) A 9:7 ratio indicates incomplete dominance.

Answer:  FALSE

Section:  4.3

51) Pattern baldness and hen/cock feathering in fowl are examples of X-linked inheritance.

Answer:  FALSE

Section:  4.12

 

52) Penetrance specifically refers to the expression of lethal genes in heterozygotes.

Answer:  FALSE

Section:  4.13

 

53) Expressivity is the term used to describe the balanced genetic output from a hemizygous condition.

Answer:  FALSE

Section:  4.13

 

54) Hemizygosity is the term one uses to describe the state of a gene that has no allele on the opposing chromosome.

Answer:  TRUE

Section:  4.11

 

55) Genomic imprinting occurs when one allele converts another.

Answer:  FALSE

Section:  4.13

 

56) Genomic anticipation refers to observations that a genetic disorder occurs at an earlier age in successive generations, whereas genetic imprinting occurs when gene expression varies depending on parental origin.

Answer:  TRUE

Section:  4.13

 

57) Gain of function mutations are generally dominant since one copy in a diploid organism is sufficient to alter the normal phenotype.

Answer:  TRUE

Section:  4.1

 

58) Assume that a mutation occurs in the gene responsible for the production of hexosaminidase A, such that only about 50% of the enzyme activity is found in the heterozygote compared with a homozygous normal individual. If heterozygotes are phenotypically normal, we would say that the mutant allele is recessive to its normal allele.

Answer:  TRUE

Section:  4.1

59) Alleles that are masked by an epistatic locus are said to be hypostatic to the genes at that locus.

Answer:  TRUE

Section:  4.8

 

60) One result of X-linkage is a crisscross pattern of inheritance in which sons express recessive genes of their fathers and daughters express recessive genes of their mothers.

Answer:  FALSE

Section:  4.12

61) The term expressivity defines the percentage of individuals who show at least some degree of expression of a mutant genotype.

Answer:  FALSE

Section:  4.13

Chapter 11   DNA Replication and Recombination

 

1) Which of the following terms accurately describes the replication of DNA in vivo?

  1. A) conservative
  2. B) dispersive
  3. C) semidiscontinuous
  4. D) nonlinear
  5. E) nonreciprocal

Answer:  C

Section:  11.1

 

2) Which term(s) accurately reflect(s) the nature of replication of the chromosome in E. coli?

  1. A) bidirectional and fixed point of initiation
  2. B) unidirectional and reciprocal
  3. C) unidirectional and fixed point of initiation
  4. D) multirepliconic and telomeric
  5. E) bidirectional and multirepliconic

Answer:  A

Section:  11.2, 11.3, 11.4

 

3) DNA polymerase III adds nucleotides ________.

  1. A) to the 3 end of the RNA primer
  2. B) to the 5 end of the RNA primer
  3. C) in the place of the primer RNA after it is removed
  4. D) to both ends of the RNA primer
  5. E) to internal sites in the DNA template

Answer:  A

Section:  11.2

 

4) DNA polymerase I is thought to add nucleotides ________.

  1. A) to the 5 end of the primer
  2. B) to the 3 end of the primer
  3. C) in the place of the primer RNA after it is removed
  4. D) on single-stranded templates without need for an RNA primer
  5. E) in a 5 to 5 direction

Answer:  C

Section:  11.2, 11.3

 

5) Structures located at the ends of eukaryotic chromosomes are called ________.

  1. A) centromeres
  2. B) telomerases
  3. C) recessive mutations
  4. D) telomeres
  5. E) permissive mutations

Answer:  D

Section:  11.7

6) Which cluster of terms accurately reflects the nature of DNA replication in prokaryotes?

  1. A) fixed point of initiation, bidirectional, conservative
  2. B) fixed point of initiation, unidirectional, conservative
  3. C) random point of initiation, bidirectional, semiconservative
  4. D) fixed point of initiation, bidirectional, semiconservative
  5. E) random point of initiation, unidirectional, semiconservative

Answer:  D

Section:  11.2, 11.3, 11.4

 

7) The discontinuous aspect of replication of DNA in vivo is caused by ________.

  1. A) polymerase slippage
  2. B) trinucleotide repeats
  3. C) the 5 to 3 polarity restriction
  4. D) topoisomerases cutting the DNA in a random fashion
  5. E) sister-chromatid exchanges

Answer:  C

Section:  11.3, 11.4, 11.5

 

 

8) Assume that a culture of E. coli was grown for approximately 50 generations in 15N (provided in the medium in the ammonium ion), which is a heavy isotope of nitrogen (14N). You extract the DNA from the culture, and it has a density of 1.723 gm/cm3 (water = 1.00 gm/cm3). From the literature, you determine that DNA containing only the common form of nitrogen, 14N, has a density of 1.700 gm/cm3. Bacteria from the 15N culture were washed in buffer and transferred to 14N medium for one generation immediately after which the DNA was extracted and its density determined.

 

(a) What would be the expected density of the extracted DNA?

 

(b) After you heat the extracted DNA until it completely denatures (95oC for 15 minutes), what would you expect the density of the DNA in the denatured extract to be? For the purposes of this question, assume that DNA has the same density regardless of whether it is single- or double-stranded.

 

(c) Assuming that the molar percentage of adenine in the extracted DNA was 20%, what would be the expected molar percentages of the other nitrogenous bases in this DNA?

 

(d) Assume that a fraction of the extracted DNA was digested to completion with the enzyme snake venom diesterase. This enzyme cleaves between the phosphate and the 3 carbon. Present a simplified diagram that would illustrate the structure of the predominant resulting molecule.

Answer:

(a) approximately 1.712

(b) 1.723 and 1.700

(c) thymine = 20%, guanine = 30%, cytosine = 30%

(d)

 

 

Section:  11.1

 

 

9) Refer to the following diagram of a generalized tetranucleotide to answer questions (a) through (e).

 

 

(a) Is this a DNA or an RNA molecule? ________

 

(b) Place an X (in one of the circles in the diagram) at the 3 end of this tetranucleotide.

 

(c) Given that the DNA strand, which served as a template for the synthesis of this tetranucleotide, was composed of the bases 5-ACAG-3, fill in the parentheses (in the diagram) with the expected bases.

 

(d) Suppose that one of the precursors for this tetranucleotide was a 32P-labeled guanine nucleoside triphosphate (the innermost phosphate containing the radioactive phosphorus).Circle the radioactive phosphorus atom as it exists in the tetranucleotide.

 

(e) Given that spleen diesterase (breaks between the phosphate and the 5 carbon) digests the pictured tetranucleotide, which base(s) among the breakdown products would be expected to be attached to the 32P?

Answer:

(a) DNA

(b) place in bottom circle

(c) 3-TGTC-5

(d) phosphate on the 5 side of the guanine

(e) thymine closer to the 5 end

Section:  11.2, 11.3

 

10) Assume that you are microscopically examining mitotic metaphase cells of an organism with a 2n chromosome number of 4 (one pair metacentric and one pair telocentric). Assume also that the cell passed through one S phase labeling (innermost phosphate of dTTP radioactive) just prior to the period of observation. Assuming that the circle below represents a cell, draw its chromosomes and the autoradiographic pattern you would expect to see.

Answer:

 

Section:  11.1

 

11) The Meselson and Stahl experiment provided conclusive evidence for the semiconservative replication of DNA in E. coli. What pattern of bands would occur in a CsCl gradient for conservative replication?

Answer:  After one generation in the 14N, there would be two bands, one heavy and one light (no intermediate). After the second generation in the 14N, there would also be two bands, one heavy and one light (no intermediate).

Section:  11.1

12) Given that the nature of DNA replication in eukaryotes is not as well understood as in prokaryotes, (a) present a description of DNA (chromosome) replication as presently viewed in eukaryotes and (b) state the differences known to exist between prokaryotic and eukaryotic DNA replication.

Answer:

(a) Eukaryotic DNA is replicated in a manner very similar to that in E. coli: bidirectional, continuous on one strand and discontinuous on the other, and similar requirements for synthesis (four deoxyribonucleoside triphosphates, divalent cation, template, and primer).

 

(b) Okazaki fragments are about one-tenth the size of those in bacteria. Different portions of the chromosome (euchromatin, heterochromatin) replicate at different times. There are multiple replication origins in eukaryotic chromosomes.

Section:  11.6

13) Each of the following terms refers to the replication of chromosomes. Describe the role (relationship) of each in (to) chromosome replication.

 

(a) Okazaki fragment

(b) Lagging strand (c)Bidirectional

Answer:

(a) Okazaki fragment is a short single-stranded stretches of DNA on the lagging strand. See figures in the Klug/Cummings text.

 

(b) Lagging strand is the side of the replication fork where synthesis is discontinuous. See figures in the Klug/Cummings text.

 

(c) Bidirectional indicates that from the point of initiation, replication occurs in both directions along the DNA. See figures in the Klug/Cummings text.

Section:  11.3, 11.4

 

14) Assume that you were growing cells in culture and had determined the cell-cycle time to be 24 hours. You introduce 3H thymidine and prepare autoradiographs of metaphase chromosomes after 48 hours. Of the chromosomes that are labeled, you expect two classes: one class that had completed one S phase in the label, and a second class that had completed a cellular division and an additional S phase in the label. Draw the DNA (double-stranded) labeling pattern for each chromosome that you would expect to find in these two types of metaphase chromosomes. (Use a broken line {- -} for labeled single strands of DNA and a solid line for unlabeled single strands of DNA.)

 

(a) metaphase chromosome having replicated once in label

(b) metaphase chromosome having gone through two S phases in label

Answer:

(a)

 

(b)

 

 

Section:  11.1

 

15) Below is a diagram of DNA replication as currently believed to occur in E. coli. From specific points, arrows lead to numbers. Answer the questions relating to the locations specified by the numbers.

 

 

(1) Which end (5 or 3) of the molecule is here?

(2) Which enzyme is probably functioning here to deal with supercoils in the DNA?

(3) Which enzyme is probably functioning here to unwind the DNA?

(4) Which nucleic acid is probably depicted here?

(5) What are these short DNA fragments usually called?

(6) Which enzyme probably functions here to couple these two newly synthesized fragments of DNA?

(7) Is this strand the leading or lagging strand?

(8) Which end (5 or 3) of the molecule is here?

Answer:

(1)        5

(2)        gyrase

(3)        helicase

(4)        RNA

(5)        Okazaki fragments

(6)        ligase

(7)        lagging

(8)        5

Section:  11.2, 11.3, 11.4

 

 

16) Assume that you grew a culture of E. coli for many generations in medium containing 15N (from the ammonium ion), a heavy isotope of nitrogen. You extract DNA from a portion of the culture and determine its density to be 1.723 gm/cm3 (call this sample A). You then wash the remaining E. coli cells and grow them for one generation in 14N, extract the DNA from a portion of the culture, and determine its density to be 1.715 gm/cm3 (call this sample B). You let the culture grow for one more generation in 14N, and extract the DNA (call this sample C). Each sample of DNA (A, B, and C) is then heated to completely denature the double-stranded structures, cooled quickly (to keep the strands separate), and subjected to ultracentrifugation. Present the centrifugation profiles for heat-denatured DNA (samples A, B, and C) that you would expect. Use the graph below. (Note: Although not the case, assume that single-stranded DNA has the same density as double-stranded DNA.)

 

 

 

Answer:

 

 

Section:  11.1

 

17) Assume that you grew a culture of E. coli for many generations in medium containing 15N (from the ammonium ion), a heavy isotope of nitrogen. You extract DNA from a portion of the culture and determine its density to be 1.723 gm/cm3 (call this sample A). You then wash the remaining E. coli cells and grow them for one generation in 14N, and extract the DNA from a portion of the culture (call this sample B). You let the culture grow for one more generation in 14N, and extract the DNA (call this sample C). Each sample of DNA (A, B, and C) is then subjected to ultracentrifugation. Present the centrifugation profiles that you would expect under (a) semiconservative replication and (b) conservative replication. (Note: Assume that unlabeled [14N] DNA has a density of 1.700 gm/cm3.)

Answer:

 

Section:  11.1

 

18) List four enzymes known to be involved in the replication of DNA in bacteria.

Answer:  Appropriate answers would include any four of the following: DNA polymerase I, III, ligase, RNA primase, helicase, gyrase

Section:  11.2, 11.3, 11.4

 

19) Which structural circumstance in DNA sets up the requirement for its semidiscontinuous nature of replication?

Answer:  5 > 3 polarity restrictions of DNA synthesis and the antiparallel orientation of the DNA strands in DNA

Section:  11.2, 11.3, 11.4

 

20) As unwinding of the helix occurs during DNA replication, tension is created ahead of the replication fork. Describe the nature of this tension and state the manner in which this tension is resolved.

Answer:  supercoiling; DNA gyrase

Section:  11.2, 11.3, 11.4

 

21) The complex of proteins that is involved in the replication of DNA is called a(n) ________.

Answer:  replisome

Section:  11.2

 

 

22) Given that the origin of replication is fixed in E. coli, what signals the location of the origin?

Answer:  a region called oriC, which consists of about 250 base pairs characterized by repeating sequences of 9 and 13 bases (9mers and 13mers)

Section:  11.3

23) Which protein is responsible for the initial step in unwinding the DNA helix during replication of the bacterial chromosome?

Answer:  DnaA

Section:  11.3

 

24) During DNA replication, what is the function of RNA primase?

Answer:  RNA primase provides a free 3-OH upon which DNA polymerization depends.

Section:  11.3, 11.4

 

25) Compare the rate of DNA replication in prokaryotes and eukaryotes.

Answer:  Eukaryotic DNA polymerases synthesize DNA at a rate 25 times slower (about 2000 nucleotides per minute) than do prokaryotes.

Section:  11.6

 

26) What is the name of the replication unit in prokaryotes, and how does it differ in eukaryotes?

Answer:  replicon; one replicon in prokaryotes, multiple replicons in eukaryotes

Section:  11.1, 11.3, 11.6

 

27) Describe the DNA base sequence arrangement at the end of the Tetrahymena chromosome and the resolution of DNA replication at the end of a linear DNA strand.

Answer:  Telomeres terminate in a 5-TTGGGG-3 sequence, and telomerase is capable of adding repeats to the ends, thus allowing the completion of replication without leaving a gap and shortening the chromosome following each replication.

Section:  11.7

 

28) Describe a somewhat extraordinary finding related to the Tetrahymena telomerase enzyme.

Answer:  The enzyme contains a short piece of RNA that is essential for its catalytic activity.

Section:  11.7

 

29) What term is used to describe genetic exchange at equivalent positions along two chromosomes with substantial DNA sequence homology?

Answer:  general or homologous recombination

Section:  11.8

 

30) Describe the function of the RecA protein.

Answer:  The RecA protein promotes the exchange of reciprocal single-stranded DNA molecules by enhancing hydrogen bond formation during strand displacement.

Section:  11.8

 

 

31) What three possible models were suggested to originally describe the nature of DNA replication?

Answer:  conservative, semiconservative, dispersive

Section:  11.1

32) Given the diagram below, assume that a G1 chromosome (left) underwent one round of replication in 3H-thymidine and the metaphase chromosome (right) had both chromatids labeled. Which of the following replicative models (conservative, dispersive, semiconservative) could be eliminated by this observation?

 

 

Answer:  conservative

Section:  11.3

 

33) Meselson and Stahl determined that DNA replication in E coli is semiconservative. What additive did they initially supply to the medium in order to distinguish new from old DNA?

Answer:  15N

Section:  11.1

 

34) Briefly describe what is meant by the term autoradiography and identify a classic experiment that used autoradiography to determine the replicative nature of DNA in eukaryotes.

Answer:  Autoradiography is a technique that allows an isotope to be detected within a cell; the Taylor, Woods, and Hughes (1957) experiment used 3H-thymidine.

Section:  11.1

 

35) What primary ingredients, coupled with DNA polymerase I, are needed for the in vitro synthesis of DNA?

Answer:  dNTP, DNA template, primer DNA or RNA, Mg++ (appropriate buffering, temperature, and salt concentrations might be considered secondary ingredients)

Section:  11.2

 

36) DNA replication in vivo requires a primer with a free 3 end. What molecular species provides this 3 end, and how is it provided?

Answer:  The free 3 end is provided by an RNA primer; it is provided by the enzymatic activity of RNA primase.

Section:  11.2, 11.3

 

 

37) DNA replication occurs in the 5 to 3 direction; that is, new nucleoside triphosphates are added to the 3 end.

Answer:  TRUE

Section:  11.2, 11.3

 

38) DNA replicates conservatively, which means that one of the two daughter double helices is old and the other is new.

Answer:  FALSE

Section:  11.2

39) DNA strand replication begins with an RNA primer.

Answer:  TRUE

Section:  11.3, 11.4

 

40) In general, DNA replicates semiconservatively and bidirectionally.

Answer:  TRUE

Section:  11.1

 

41) In ligase-deficient strains of E. coli, DNA and chromosomal replication are unaltered because ligase is not involved in DNA replication.

Answer:  FALSE

Section:  11.5

 

42) During replication, primase adds a DNA primer to RNA.

Answer:  FALSE

Section:  11.2, 11.3, 11.4

 

43) An endonuclease is involved in removing bases sequentially from one end of DNA or the other.

Answer:  FALSE

Section:  11.2, 11.3, 11.4

 

44) In the Meselson and Stahl (1958) experiment, bean plants (Vicia faba) were radioactively labeled so that autoradiographs could be made of chromosomes.

Answer:  FALSE

Section:  11.1

 

45) A nucleosome is a structure associated with the nuclear membrane. It helps maintain a stable relationship between the extracellular matrix and the membrane itself.

Answer:  FALSE

Section:  11.6

 

46) A characteristic of aging cells is that their telomeres become shorter.

Answer:  TRUE

Section:  11.7

 

 

47) Telomerase is an RNA-containing enzyme that adds telomeric DNA sequences onto the ends of linear chromosomes.

Answer:  TRUE

Section:  11.7

 

48) Bacteria are dependent on telomerase to complete synthesis of their chromosome ends.

Answer:  FALSE

Section:  11.7

 

49) Chromatin assembly factors (CAFs) move along with the replication fork and assemble new nucleosomes.

Answer:  TRUE

Section:  11.6

50) G-quartets are G-rich single-stranded tails that loop back on themselves forming G-G double stranded sections. Such looping is involved in aligning chromosomes for homologous recombination.

Answer:  FALSE

Section:  11.8

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