Gentics Ch 4, 5, 7

Question 1

A condition in which one gene pair masks the expression of a nonallelic gene pair is called ________.
Question 1 Answer

a.
codominance

b.
dominance

c.
additive alleles

d.
epistasis

e.
recessiveness

Answer 1

Epistasis

Question 2

Which mutations are generally dominant since one copy in a diploid organism is sufficient to alter the normal phenotype?
Question 2 Answer

a.
null

b.
loss of function

c.
neutral

d.
gain of function

e.
conditional

Answer 2

Gain of function

Question 3

The ABO blood group locus in humans provides an example of ________.
Question 3 Answer

a.
incomplete dominance

b.
auxotrophy

c.
conditional alleles

d.
multiple alleles

e.
epistasis

Answer 3

Multiple alleles

Question 4

With incomplete dominance, a likely ratio resulting from a monohybrid cross would be ________.
Question 4 Answer

a.
9:3:3:1

b.
3:1

c.
1:2:2:4

d.
3:3

e.
1:2:1

Answer 4

1:2:1

Question 5

A gain-of-function mutation _______.
Question 5 Answer

a.
results in an increased quantity of the normal gene product

b.
is usually recessive

c.
results in absence of the gene product

d.
is the wild-type allele

Answer 5

results in an increased quantity of the normal gene product

Question 6

The white-eyed 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?
Question 6 Answer

a.
females wild type, males white eyed

b.
females white eyed; males wild type

c.
females half wild type, half white eyed; males white eyed

d.
all wild type

e.
all white eyed

Answer 6

females wild type, males white eyed

Question 7

An allele of RNA polymerase in Drosophila demonstrates a recessive lethal inheritance pattern. Which of the following is true?
Question 7 Answer

a.
Two heterozygotes will have offspring with a 2:1 pattern.

b.
Two homozygous recessive parents will have 100% homozygous offspring.

c.
The threshold effect is not seen in recessive lethality.

d.
Homozygous lethal genes will always demonstrate a gain of function pattern.

e.
Homozygous recessive offspring will never be seen.

Answer 7

Homozygous recessive offspring will never be seen.

Question 8

With ________, there will be more than two genetic alternatives for a given locus.
Question 8 Answer

a.
gain of function mutant

b.
codominance

c.
epistasis

d.
multiple alleles

e.
incomplete dominance

Answer 8

multiple alleles

Question 9

Complementation analysis is used to determine _______.
Question 9 Answer

a.
whether two mutations that produce the same phenotype reside in the same or different genes

b.
whether a gene is X-linked or autosomal

c.
whether two alleles are codominant

d.
whether a gene is pleiotropic

Answer 9

whether two mutations that produce the same phenotype reside in the same or different genes

Question 10

Which of the following symbols indicates a wild-type allele?
Question 10 Answer

a.
+

b.
D

c.
e

d.
R1

Answer 10

+

Question 11

What is the most prevalent form of an allele called?
Question 11 Answer

a.
neutral

b.
recessive

c.
dominant

d.
normal

e.
wild type

Answer 11

Wild type

Question 12

Because of the mechanism of sex determination, males of many species can be neither homozygous nor heterozygous. Such males are said to be ________.
Question 12 Answer

a.
recessive

b.
dominant

c.
complementary

d.
hemizygous

e.
None of the answers listed are correct.

Answer 12

hemizygous

Question 13

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 ________ to its normal allele.
Question 13 Answer

a.
dominant

b.
gain of function

c.
recessive

d.
auxotrophic

e.
epistatic

Answer 13

recessive

Question 14

What term is used to express the idea that several genes exert influence over the same characteristic?
Question 14 Answer

a.
terminal interaction

b.
coextension

c.
co-adhesion

d.
transformation

e.
gene interaction

Answer 14

gene interaction

Question 15

In a mating between individuals with the genotypes IAi × ii, what percentage of the offspring are expected to have the O blood type?
Question 15 Answer

a.
75%

b.
100%

c.
0%

d.
25%

e.
50%

Answer 15

50%

Question 16

What is the blood type of individuals who cannot add the terminal sugar to the H substance?
Question 16 Answer

a.
AB

b.
A

c.
Bombay phenotype

d.
O

e.
B

Answer 16

O

Question 17

A ________ is one whose expression is influenced by some environmental condition.
Question 17 Answer

a.
positional effect

b.
conditional mutant

c.
multiple allele

d.
X-linked allele

e.
expressive allele

Answer 17

conditional mutant

Question 18

Multiple mutations that are found to be present in a single gene are said to belong to the same ________ group.
Question 18 Answer

a.
transfer

b.
phenotypic

c.
allelic

d.
complementation

e.
expression

Answer 18

complementation

Question 19

Which of the following statements is true?
Question 19 Answer

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

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

c.
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.

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

e.
Genomic imprinting occurs when one allele converts another.

Answer 19

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.

Question 20

A situation in which there are more than two alternative forms of a given gene would be called ________.
Question 20 Answer

a.
multiple alleles

b.
alternation of generations

c.
incomplete dominance

d.
hemizygosity

e.
codominance

Answer 20

multiple alleles

Question 21

Which of the following is an example of sex-limited inheritance?
Question 21 Answer

a.
hemophilia

b.
beard formation in humans

c.
cat fur length

d.
human baldness

e.
hair color in humans

Answer 21

beard formation in humans

Question 22

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?
Question 22 Answer

a.
100%

b.
1/2

c.
zero

d.
1/4

e.
1/3

Answer 22

1/2

Question 23

What would be a typical phenotypic monohybrid ratio in which a lethal allele is involved?
Question 23 Answer

a.
9:3:3:1

b.
3:1

c.
6:2:3:1

d.
2:1

e.
13:5

Answer 23

2:1

Question 24

Name three modes of inheritance that are influenced by the sex of individuals.
Question 24 Answer

a.
X-linked, sex-influenced, sex-limited

b.
epistasis, conditional alleles, expressivity

c.
conditional alleles, sex-limited, X-linked

d.
sex-influenced, epistasis, sex-limited

e.
penetrance, X-limited inheritance, X-linked inheritance

Answer 24

X-linked, sex-influenced, sex-limited

Question 25

Why can multiple alleles only be studied in populations? Question 25 Answer a. Multiple allelism always involves at least two recessive alleles. A large number of individuals must be analyzed to determine the mode of inheritance. b. Families contain a limited number of alleles, but populations can contain all of the possibilities. c. A large number of crosses must be carried out to determine the mode of inheritance. d. Any individual diploid organism can have, at most, two different alleles at a single locus.

Answer 25

Any individual diploid organism can have, at most, two different alleles at a single locus.

Question 26

With which of the following would hemizygosity most likely be associated? Question 26 Answer a. codominance b. sex-limited inheritance c. X-linked inheritance d. incomplete dominance e. trihybrid crosses

Answer 26

X-linked inheritance

Question 27

Which of the following reflects the genotype of an individual in the phenotype? Question 27 Answer a. incomplete penetrance b. complete dominance c. variable expressivity d. position effect

Answer 27

complete dominance

Question 28

Alleles that are masked by an epistatic locus are said to be ________ to the genes at that locus. Question 28 Answer a. conditional b. functional c. auxotrophic d. hypostatic e. complementary

Answer 28

hypostatic

Question 29

Achondroplasia is a form of human dwarfism. If two individuals with achondroplasia have children with the following ratio, 2 dwarf to 1 wild type, what is the means of inheritance of this phenotype? Question 29 Answer a. epistasis b. simple dominance c. dominant lethal d. recessive lethal e. simple recessive

Answer 29

dominant lethal

Question 30

Typically, when one wishes to represent a gene, the symbol used is _________. Question 30 Answer a. in all upper-case letters b. in italics c. in all lowercase letters d. in bold print e. underlined

Answer 30

in italics

Question 31

The deficiency of the enzyme glucose-6-phosphate dehydrogenase (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. What fraction of their sons would be expected to have G6PD? Question 31 Answer a. 1/3 b. zero c. 1/2 d. 1/4 e. 100%

Answer 31

1/2

Question 32

In imprinting, allelic expression is based on which parent the allele came from. The physical location of a gene in relation to other genetic material is known as __________. Question 32 Answer a. expressivity b. penetrance c. position effect d. auxotrophic mutation

Answer 32

position effect

Question 33

A gene in which the heterozygous condition is displayed differently in males and females is referred to as _______. Question 33 Answer a. X-linked b. sex-influenced c. imprinting d. sex-limited

Answer 33

sex-influenced

Question 34

What is a significant difference between X-linked and sex-influenced inheritances? Question 34 Answer a. Sex-influenced inheritance requires epistasis. X-linked inheritance does not. b. In X-linked inheritance, the gene in question is on the X chromosome; in sex-influenced inheritance, the gene is autosomal. c. There are no differences. They are the same. d. X-limited inheritance is only recessive. Sex-influenced inheritance can be recessive or dominant. e. X-linked inheritance affects females and sex-influenced inheritance affects males.

Answer 34

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

Question 35

Which of the following is true about X-linkage? Question 35 Answer a. X linkage demonstrates that only the wild-type allele is the dominant allele. b. Females will only express dominant alleles. c. 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. d. One result of X-linkage is a crisscross pattern of inheritance in which daughters express recessive genes of their fathers and sons express recessive genes of their mothers. e. Males are more liable to express recessive alleles as they are hemizygous.

Answer 35

Males are more liable to express recessive alleles as they are hemizygous.

Question 36

Which of the following is true? Question 36 Answer a. A neutral mutation leads to no discernable phenotype. b. A neutral mutation leads to a phenotype that can help or hurt the organism depending on the environment. c. A neutral allele leads to a change in function in a protein that neither harms nor helps an organism. d. Each biochemical pathway is governed by one gene. e. A mutation in the DNA can be observed at the macroscopic level even if there's no change in phenotype.

Answer 36

A neutral mutation leads to no discernable phenotype.

Question 37

A mutation in a gene often results in a reduction of the product of that gene. The term for this type of mutation is ________. Question 37 Answer a. multiple allelism b. codominance c. incomplete dominance d. loss of function or null (in the case of complete loss) e. gain of function

Answer 37

loss of function or null (in the case of complete loss)

Question 38

Which of the following statements is always true when mutations occur in genes whose products are essential to an organism's survival? Question 38 Answer a. A homozygote for a recessive lethal allele will not survive. b. One normal copy of the gene will allow survival. c. The heterozygote always has a normal phenotype. d. Reversion of the mutation must occur for the organism to survive. e. If the gene product is essential for survival, having two mutant alleles means the organism will not produce the gene product at all.

Answer 38

A homozygote for a recessive lethal allele will not survive.

Question 39

What is the term for a gene mutation that leads to a myriad of disparate effects? Question 39 Answer a. complementation b. lethal allele c. multiple allele d. pleiotropy e. expressivity

Answer 39

pleiotropy

Question 40

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. What is the term for this allelic relationship? Question 40 Answer a. positional effect b. incomplete dominance c. epistasis d. codominance e. multiple alleles

Answer 40

incomplete dominance

Question 41

In a mating between individuals with the genotypes IAi × ii, what percentage of the offspring are expected to have the O blood type? Question 3 Answer a. 75% b. 100% c. 0% d. 25% e. 50%

Answer 41

50%

Question 42

Alleles that are masked by an epistatic locus are said to be ________ to the genes at that locus. Question 2 Answer a. conditional b. functional c. auxotrophic d. hypostatic e. complementary

Answer 42

hypostatic

Question 43

Which of the following DNA markers cannot be used for mapping? Question 6 Answer a. SNPs b. RFLPs c. microsatellites d. chiasmata

Answer 43

chiasmata

Question 44

In imprinting, allelic expression is based on which parent the allele came from. The physical location of a gene in relation to other genetic material is known as __________. Question 7 Answer a. expressivity b. penetrance c. position effect d. auxotrophic mutation

Answer 44

position effect

Question 45

Complementation analysis is used to determine _______. Question 9 Answer a. whether two mutations that produce the same phenotype reside in the same or different genes b. whether a gene is X-linked or autosomal c. whether two alleles are codominant d. whether a gene is pleiotropic

Answer 45

whether two mutations that produce the same phenotype reside in the same or different genes

Question 46

A ________ is one whose expression is influenced by some environmental condition. Question 10 Answer a. X-linked allele b. positional effect c. expressive allele d. multiple allele e. conditional mutant

Answer 46

conditional mutant

Question 47

An allele of RNA polymerase in Drosophila demonstrates a recessive lethal inheritance pattern. Which of the following is true? Question 11 Answer a. Two heterozygotes will have offspring with a 2:1 pattern. b. Two homozygous recessive parents will have 100% homozygous offspring. c. The threshold effect is not seen in recessive lethality. d. Homozygous lethal genes will always demonstrate a gain of function pattern. e. Homozygous recessive offspring will never be seen

Answer 47

Homozygous recessive offspring will never be seen.

Question 48

Why do mapping experiments become less accurate when the distances between genes become large? Question 12 Answer a. Multiple crossovers are more common. b. Crossover gametes become less common. c. Recombination occurs less frequently in long chromosomes. d. Interference is greater when the distance between genes is large.

Answer 48

Multiple crossovers are more common.

Question 49

Achondroplasia is a form of human dwarfism. If two individuals with achondroplasia have children with the following ratio, 2 dwarf to 1 wild type, what is the means of inheritance of this phenotype? Question 13 Answer a. epistasis b. simple dominance c. dominant lethal d. recessive lethal e. simple recessive

Answer 49

dominant lethal

Question 50

The deficiency of the enzyme glucose-6-phosphate dehydrogenase (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. What fraction of their sons would be expected to have G6PD? Question 14 Answer a. 1/3 b. zero c. 1/2 d. 1/4 e. 100%

Answer 50

1/2

Question 51

When analyzing three genes that reside on the same chromosome, the expected frequency of double-crossover events can be determined by multiplying the frequency of single crossovers between each pair of genes. What would cause the number of observed double-crossover events to be less than the expected value? Question 15 Answer a. positive interference b. negative interference c. the Poisson distribution d. the coefficient of coincidence (C)

Answer 51

positive interference

Question 52

A gain-of-function mutation _______. Question 16 Answer a. results in an increased quantity of the normal gene product b. is usually recessive c. results in absence of the gene product d. is the wild-type allele

Answer 52

results in an increased quantity of the normal gene product

Question 53

Which of the following scenarios would erroneously lead you to believe two genes reside on different chromosomes when they in fact are on the same chromosome? Question 20 Answer a. too large a sample size b. the genes are very far apart on the same chromosome, such that there is never a crossover between them c. a mating between consanguineous individuals d. the genes are very close together on the chromosome, such that there is never a crossover between them e. the genes are very far apart on the same chromosome, such that there is always a crossover between them

Answer 53

the genes are very far apart on the same chromosome, such that there is always a crossover between them

Question 54

A mutation in a gene often results in a reduction of the product of that gene. The term for this type of mutation is ________. Question 21 Answer a. multiple allelism b. codominance c. incomplete dominance d. loss of function or null (in the case of complete loss) e. gain of function

Answer 54

loss of function or null (in the case of complete loss)

Question 55

hich of the following statements is true? Question 22 Answer a. A centromere and its surrounding genes constitute a linkage group. b. The chromosomal theory of inheritance denotes that linked alleles will never be separated. c. Linkage without crossing over leads to all recombinant chromosomes. d. The linkage ratio is best seen in genes on nonhomologous chromosomes. e. If two gene loci are on nonhomologous chromosomes, genes at these loci are expected to assort independently.

Answer 55

If two gene loci are on nonhomologous chromosomes, genes at these loci are expected to assort independently.

Question 56

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. What is the term for this allelic relationship? Question 23 Answer a. positional effect b. incomplete dominance c. epistasis d. codominance e. multiple alleles

Answer 56

incomplete dominance

Question 57

Which of the following best describes why mapping is most accurate when genes are close together on a chromosome? Question 24 Answer a. The centromere gets in the way. b. This is not true; relative distance of two loci on a chromosome has no effect on accuracy of mapping. c. This is not true; mapping genes is most accurate when genes are far away from each other. d. Double crossover events yield a result that looks the same as no crossover in a two gene mapping experiment and this throws off the calculations. e. Double crossover events yield a result that looks the same as one crossover in a two gene mapping experiment and this throws off the calculations.

Answer 57

Double crossover events yield a result that looks the same as no crossover in a two gene mapping experiment and this throws off the calculations.

Question 58

Because of the mechanism of sex determination, males of many species can be neither homozygous nor heterozygous. Such males are said to be ________. Question 25 Answer a. recessive b. dominant c. complementary d. hemizygous e. None of the answers listed are correct.

Answer 58

hemizygous

Question 59

Which of the following is an example of positive interference? Question 26 Answer a. An actively transcribed gene is less likely to undergo crossover than a quiescent one. b. Double crossovers do not occur. c. A single crossover stimulates further recombination. d. A crossover in one region inhibits crossovers in nearby regions. e. Crossovers will not occur near centromeres.

Answer 59

A crossover in one region inhibits crossovers in nearby regions.

Question 60

Multiple mutations that are found to be present in a single gene are said to belong to the same ________ group. Question 27 Answer a. transfer b. phenotypic c. allelic d. complementation e. expression

Answer 60

complementation

Question 61

What region is the major control center of X inactivation in mammals? Question 1 Answer a. Xic b. MSY c. SRY d. Barr Body e. NRY

Answer 61

Xic

Question 62

Give the sex of the following Drosophila assuming that the autosomes are present in the normal number. XO; XY; XXY. Answers are in order (respectively). Question 2 Answer a. male; male; male b. female; male; male c. female; male; female d. male; female; female e. male; male; female

Answer 62

male; male; female

Question 63

A color-blind, chromatin-positive male child (one Barr body) has a maternal grandfather who was color blind. The boy's mother and father are phenotypically normal. What needed to occur to have this genetic outcome? Question 3 Answer a. The mother must be heterozygous and underwent nondisjunction at meiosis I. b. The mother is homozygous recessive and underwent nondisjunction in meiosis I or II. c. The chromosomal doubling effect of meiosis II occurred in the father. d. The mother must be heterozygous and underwent nondisjunction at meiosis II. e. Nondisjunction in meiosis I of the father occurred.

Answer 63

The mother must be heterozygous and underwent nondisjunction at meiosis II.

Question 64

Which of the following statements is false? Question 4 Answer a. Dosage compensation is accomplished in humans by inactivation of the Y chromosome. b. In a cell with X chromosomes lacking the XIC, there is still X inactivation. c. A typical XX human female has one Barr body. d. An individual with Turner Syndrome has no Barr bodies. e. An individual with Klinefelter syndrome generally has one Barr body.

Answer 64

Dosage compensation is accomplished in humans by inactivation of the Y chromosome.

Question 65

Assume that a man who carries an X-linked gene has children. Assuming normal meiosis and random combination of gametes, the man would pass this gene to ________. Question 5 Answer a. half of his sons b. all of his sons c. half of his daughters d. all of his daughters e. all of his children

Answer 65

all of his daughters

Question 66

In humans, the male is the ________ sex. Question 6 Answer a. heteromorphic b. heterogametic c. monogametic d. homomorphic e. homogametic

Answer 66

heterogametic

Question 67

Jacobs syndrome in humans, which is manifested by a higher than average stature and potential behavioral problems, is caused by which chromosomal condition? Question 7 Answer a. 47, 21+ b. 47, XXY c. triploidy d. 45, X e. 47, XYY

Answer 67

47, XYY

Question 68

One form of hemophilia is caused by a sex-linked recessive gene. Assume that a man with hemophilia marries a phenotypically normal woman whose father had hemophilia. What is the probability that they will have a daughter with hemophilia? (Note: In this problem, you must include the probability of having a daughter in your computation of the final probability.) Question 8 Answer a. 1/2 b. 3/4 c. 1/8 d. 1/4 e. 1/16

Answer 68

1/4

Question 69

Which of the following is TRUE of both Klinefelter syndrome and Turner syndrome? Question 9 Answer a. Both are the result of mitotic errors early in development. b. It is the mechanism by which dizygotic, but not monozygotic, twins are produced. c. Both typically result from nondisjunction. d. Both give rise to individuals who have external male genitalia.

Answer 69

Both typically result from nondisjunction.

Question 70

What is the ratio of male to female conceptions in a population called? Question 10 Answer a. anomalous gender reorder calculation b. conception birth order number c. gender order d. secondary sex ratio e. primary sex ratio

Answer 70

primary sex ratio

Question 71

In Drosophila, the female is the ________ sex. Question 11 Answer a. mosaic b. homogametic c. isogametic d. heterogametic e. genic balance

Answer 71

homogametic

Question 72

Which of the following statements is true regarding Drosophila? Question 12 Answer a. The ratio of X to Y chromosomes determines fly sex. b. The Y chromosome plays no role on fly sex determination but does contain genes for fly reproduction. c. The Y chromosome determines male flies. d. The Y chromosome plays no role in fly sex determination or fly reproduction. e. The ratio of autosomes to fly Y and X chromosomes determines fly sex.

Answer 72

The Y chromosome plays no role on fly sex determination but does contain genes for fly reproduction.

Question 73

The sex of birds, some insects, and other organisms is determined by a ZW chromosomal arrangement in which the males have like sex chromosomes (ZZ) and females are ZW (similar to XY in humans). Assume that a recessive lethal allele on the Z chromosome causes death of an embryo in birds. What sex ratio would result in the offspring if a cross were made between a male heterozygous for the lethal allele and a normal female? Question 13 Answer a. 1:2 male to female b. 4:1 male to female c. 1:1 male to female d. 3:1 male to female e. 2:1 male to female

Answer 73

2:1 male to female

Question 74

Under what condition might a human female have the XY sex chromosome complement? Question 14 Answer a. She has an XX chromosome and a Y chromosome. b. The X chromosome has a mutation such that it is able to overpower the Y chromosome. c. The Y chromosome has an active Xist gene on it. d. This is not possible. e. This female would have one complete X chromosome and a Y chromosome that lacks SRY.

Answer 74

This female would have one complete X chromosome and a Y chromosome that lacks SRY.

Question 75

In Drosophila, sex is determined by a balance between the number of haploid sets of autosomes and the number of ________. Question 15 Answer a. Y chromosomes b. telomeres c. centromeres d. X chromosomes e. nucleolar organizers

Answer 75

X chromosomes

Question 76

X-linked genes in female mammals often demonstrate ________. Question 16 Answer a. heterochromatin formation b. incomplete dominance c. phenotypic mosaicism d. nonrecombination during meiosis e. underrepresentation in the genome

Answer 76

phenotypic mosaicism

Question 77

Glucose-6-phosphate dehydrogenase (G6PD) deficiency is inherited as an X-linked recessive gene in humans. A woman whose father suffered from G6PD marries a normal man. What percentage of their sons is expected to be G6PD? Question 17 Answer a. 100% b. 50% c. 75% d. 25% e. 0%

Answer 77

50%

Question 78

What does the nonrecombining region of the Y contain? Question 18 Answer a. the genes that have homologues on the X chromosome b. SRY c. the centromere d. the genes that have homologues on the X chromosome, SRY, and the centromere e. SRY and the centromere

Answer 78

SRY and the centromere

Question 79

A color-blind woman with Turner syndrome (XO) has a father who is color blind. Given that the gene for the color-blind condition is recessive and X-linked, provide a likely explanation for the origin of the color-blind and cytogenetic conditions in the woman. Question 19 Answer a. nondisjunction in the father at meiosis I b. nondisjunction in the mother in meiosis I or II c. nondisjunction in the father in meiosis I or II d. no abnormalities had to occur to produce this daughter e. nondisjunction in the mother in meiosis I and in the father in meiosis II

Answer 79

nondisjunction in the mother in meiosis I or II

Question 80

Give the sex of the following people assuming that the autosomes are present in the normal number. XO; XY; XXY. Answers are in order (respectively). Question 20 Answer a. female; male; female b. female; male; male c. male; male; female d. male; male; male e. male; female; female

Answer 80

female; male; female

Question 81

What are pseudoautosomal regions on the sex chromosomes? Question 21 Answer a. hemizygous regions of the X and Y chromosomes b. Homozygous regions of autosomal chromosomes c. Regions of the X and Y chromosomes that don't recombine during meiosis d. homologous regions of the X and Y chromosomes

Answer 81

homologous regions of the X and Y chromosomes

Question 82

Where is the general location of a Barr body? Question 22 Answer a. stuck in a nuclear pore b. attached to the nuclear envelope c. attached to the other X chromosome d. adjacent to the Y chromosome e. in the nucleolus

Answer 82

attached to the nuclear envelope

Question 83

In Drosophila, an individual female fly was observed to be of the XXY chromosome complement (normal autosomal complement) and to have white eyes as contrasted with the normal red eye color of wild type. The female's mother and father had red eyes. The mother, however, was heterozygous for the gene for white eyes. Knowing that white eyes are X-linked and recessive, present an explanation for the genetic and chromosomal constitution of the XXY, white-eyed individual. Question 23 Answer a. nondisjunction in meiosis I of the father b. nondisjunction in meiosis II of the mother c. nondisjunction in meiosis I or II in father d. nondisjunction in meiosis I of the mother e. nondisjunction in meiosis I of both the mother and father

Answer 83

nondisjunction in meiosis II of the mother

Question 84

For an individual with the XXY chromosomal composition, the expected number of Barr bodies in interphase cells is ________. Question 24 Answer a. variable b. two c. one d. three e. zero

Answer 84

one

Question 85

Which of the following statements below is false? Question 25 Answer a. Normally in humans, all the sons of a female homozygous for an X-linked recessive gene will inherit that trait. b. Normally in humans, a male that is carrying an X-linked dominant trait will pass it to all his daughters. c. Normally in humans, all the sons of a male showing an X-linked phenotype will inherit the trait. d. At meiosis I, the X and Y chromosomes line up as if they were homologs. e. Normally in humans, females are carriers of X-linked recessive traits if they are heterozygous.

Answer 85

Normally in humans, all the sons of a male showing an X-linked phenotype will inherit the trait.

Question 86

Which of the following human genetic conditions is missing a chromosome? Question 26 Answer a. XXXX syndrome b. Down's syndrome c. Jacob syndrome d. Turner syndrome e. Klinefelter syndrome

Answer 86

Turner syndrome

Question 87

In humans, the genetic basis for determining the sex "male" is accomplished by the presence of ________. Question 27 Answer a. one X chromosome b. a portion of the Y chromosome c. a balance between the number of X chromosomes and the number of haploid d. sets of autosomes e. high levels of estrogen

Answer 87

a portion of the Y chromosome

Question 88

A recessive gene for red-green color blindness is located on the X chromosome in humans. Assume that a woman with normal vision (her father is color blind) marries a color-blind male. What is the likelihood that this couple's first son will be color blind? Question 28 Answer a. 25% b. 50% c. 100% d. 0% e. 75%

Answer 88

50%

Question 89

Which of the following statements about XYY males is true? Question 29 Answer a. They have underdeveloped secondary sex characteristics. b. They are likely to end up in prison. c. They are generally taller than average. d. They are sterile.

Answer 89

They are generally taller than average.

Question 90

Data produced by C. Bridges in the early part of this century indicate that sex in Drosophila is determined by ________. Question 30 Answer a. the number of Y chromosomes b. the SRY gene c. the ratio of X to Y chromosomes d. a balance between the number of X chromosomes and the number of haploid sets of autosomes e. the number of X chromosomes

Answer 90

a balance between the number of X chromosomes and the number of haploid sets of autosomes