Deck 7: Sex Determination and Sex Chromosomes

Question 1

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 their first son will have hemophilia?

A)1/4
B)1/16
C)1/8
D)3/4
E)1/2

Answer 1

E

Question 2

In humans,the male is the ______sex.

A)heterogametic
B)homogametic
C)monogametic
D)homomorphic
E)heteromorphic

Answer 2

heterogametic

Question 3

Under what condition might a human female have the XY sex chromosome complement?

A)She has an XX chromosome and a Y chromosome.
B)The Y chromosome has an active Xist gene on it.
C)The X chromosome has a mutation such that it is able to overpower the Y chromosome.
D)This is not possible.
E)This female would have one complete X chromosome and a Y chromosome that lacks SRY.

Answer 3

E

Question 4

A small part of the human Y chromosome contains the gene that is responsible for determining maleness.What is the name of this gene?

A)SRY
B)Xist
C)NRY
D)Dax
E)medulla

Question 5

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?

A)75%
B)0%
C)50%
D)100%
E)25%

Question 6

The accompanying figure is a pedigree of a fairly common human hereditary trait; the boxes represent males and the circles represent females.Filled in symbols indicate the abnormal phenotype.Given that one gene pair is involved,what is the inheritance pattern of the trait?

A)X- linked dominant
B)X- linked recessive
C)epistasis
D)autosomal recessive
E)autosomal dominant

Question 7

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.

A)1/4
B)1/8
C)1/2
D)1/16
E)3/4

Question 8

The Protenor mode of sex determination is the ______ .

A)XO/YY scheme
B)XX/XO scheme
C)scheme based on single translocations in the X chromosome
D)scheme based on F plasmids inserted into the FMR- 1 gene
E)hermaphroditic scheme

Question 9

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.

A)nondisjunction in the father at meiosis I
B)no abnormalities had to occur to produce this daughter
C)nondisjunction in the father in meiosis I or II
D)nondisjunction in the other in meiosis I or II
E)nondisjunction in the mother in meiosis I and in the father in meiosis II

Question 10

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?

A)100%
B)75%
C)0%
D)25%
E)50%

Question 11

The Lygaeus mode of sex determination is the _ .

A)hermaphroditic scheme
B)scheme based on single translocations in the X chromosome
C)XX/XO scheme
D)XY/XX scheme
E)XO/YY scheme

Question 12

What does the nonrecombining region of the Y contain?

A)the genes that have homologues on the X chromosome
B)SRY
C)the centromere
D)A,B,and C
E)B and C

Question 13

Individuals have been identified who have two different karyotypes,such as 45,X/46,XY or 45,X/46,XX.Such individuals are called ______.

A)heteromorphic
B)homogametic
C)trisomic
D)mosaics
E)heterogametes

Question 14

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______ .

A)all of his sons
B)half of his daughters
C)all of his children
D)half of his sons
E)all of his daughters

Question 15

Which regions of the X chromosome recombine during meiosis?

A)the pseudoautosomal regions
B)the heterochromain
C)SRY
D)the male- specific region of the Y
E)the centromere

Question 16

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?

A)1:2 male to female
B)4:1 male to female
C)3:1 male to female
D)2:1 male to female
E)1:1 male to female

Question 17

Which of the following karyotypes would lead to male characteristics in humans?

A)XO
B)XYY
C)XXY
D)XO and XYY
E)XXY and XYY

Question 18

Klinefelter and Turner syndromes have how many chromosomes,respectively?

A)47,46
B)46,46
C)45,47
D)47,45
E)46,45

Question 19

Which of the following human genetic conditions is missing a chromosome?

A)Jacob syndrome
B)Klinefelter syndrome
C)XXXX syndrome
D)Down's syndrome
E)Turner syndrome

Question 20

Jacobs syndrome in humans,which is manifested by a higher than average stature and potential behavioral problems,is caused by which chromosomal condition?

A)45,X
B)47,XYY
C)triploidy
D)47,XXY
E)47,21+

Question 21

Where is the general location of a Barr body?

A)adjacent to the Y chromosome
B)in the nucleolus
C)attached to the other X chromosome
D)attached to the nuclear envelope
E)stuck in a nuclear pore

Question 22

How many Barr bodies would one expect to see in cells of Turner syndrome females and Klinefelter syndrome males?

A)zero and two
B)one and one
C)zero and one
D)one and zero
E)zero and zero

Question 23

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 .

A)male; female; female
B)female; male; male
C)male; male; male
D)female; male; female
E)male; male; female

Question 24

Dosage compensation in mammals typically involves the random inactivation of one of the two X chromosomes relatively early in development.Such X chromosome inactivation often leads to phenotypic mosaicism.Assume that black fur in cats is due to the X- linked recessive gene b,whereas its dominant allele B produces yellow fur. A Bb heterozygote is a mosaic called "tortoise shell" or "calico." A mating between a black male and a calico female occurred.Give the phenotypes of the offspring.

A)calico females and yellow males
B)all calico regardless of sex
C)calico females,black females,yellow makes,and black males
D)calico females,yellow females,black males,and yellow males
E)all black regardless of sex

Question 25

Which of the following statements is true regarding Drosophila?

A)The ratio of X to Y chromosomes determines fly sex.
B)The Y chromosome determines male flies.
C)The ratio of autosomes to fly Y and X chromosomes determines fly sex.
D)The Y chromosome plays no role on fly sex determination but does contain genes for fly reproduction.
E)The Y chromosome plays no role in fly sex determination or fly reproduction.

Question 26

X- linked genes in female mammals often demonstrate ______ .

A)heterochromatin formation
B)phenotypic mosaicism
C)incomplete dominance
D)underrepresentation in the genome
E)nonrecombination during meiosis

Question 27

What region is the major control center of X inactivation in mammals?

A)Xic
B)NRY
C)SRY
D)MSY
E)Barr Body

Question 28

Which of the following statements is false?

A)An individual with Klinefelter syndrome generally has one Barr body.
B)Dosage compensation is accomplished in humans by inactivation of the Y chromosome.
C)An individual with Turner Syndrome has no Barr bodies.
D)In a cell with X chromosomes lacking the XIC,there is still X inactivation.
E)A typical XX human female has one Barr body.

Question 29

Assume that you are told that a particular organism,Drosophila,has the XO chromosome complement.You are also told that the autosomal complement is a normal 2n.You know that in humans the XO complement is female determining.Would you be correct in assuming that the Drosophila sex for XO is also female? Choose the answer that includes the correct explanation.

A)No,the chromosomal basis for sex determination in Drosophila is based on the balance between the number of X chromosomes and haploid sets of autosomes.
B)Yes,because sex determination in humans and insects is essentially the same.
C)Yes,the presence of an X chromosome determines a female in both organisms.
D)No,sex determination in Drosophila is dependent on the presence or absence of the Y chromosome.
E)No,it takes two X chromosomes to produce a female in humans and a Y chromosome to produce a male in Drosophila.

Question 30

What is the ratio of male to female conceptions in a population called?

A)secondary sex ratio
B)conception birth order number
C)primary sex ratio
D)anomalous gender reorder calculation
E)gender order

Question 31

A cross is made between a female calico cat and a male cat having the gene for black fur on his X chromosome.What fraction of the offspring would one expect to be calico?

A)1/4
B)none
C)2/3
D)1/2
E)3/4

Question 32

Assuming a normal number of autosomes,what would be the sex of the following: XXY mouse,XXY Drosophila?

A)male and female,respectively
B)both neuter
C)female and female,respectively
D)male and male,respectively
E)female and male,respectively

Question 33

For an individual with the XXY chromosomal composition,the expected number of Barr bodies in interphase cells is______.

A)two
B)one
C)three
D)variable
E)zero

Question 34

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.

A)nondisjunction in meiosis I or II in father
B)nondisjunction in meiosis I of the mother
C)nondisjunction in meiosis II of the mother
D)nondisjunction in meiosis I of the father
E)nondisjunction in meiosis I of both the mother and father

Question 35

What are the sex- chromosome constitution X and Y chromosomes of the inviable offspring resulting from a cross between a white- eyed female X^w X^wY and a wild- type male normal chromosome complement in Drosophila melanogaster?

A)X⁺X^wX^w and YY
B)X⁺X^wY and X⁺X^wX^w
C)YY and X^wYY
D)X^wX^wY and YY
E)X⁺Y

Question 36

Which of the following statements below is false?

A)Normally in humans,a male that is carrying an X- linked dominant trait will pass it to all his daughters.
B)Normally in humans,females are carriers of X- linked recessive traits if they are heterozygous.
C)At meiosis I,the X and Y chromosomes line up as if they were homologs.
D)Normally in humans,all the sons of a female homozygous for an X- linked recessive gene will inherit that trait.
E)Normally in humans,all the sons of a male showing an X- linked phenotype will inherit the trait.

Question 37

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 father had red eyes,and the mother had 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.

A)nondisjunction in meiosis I of mother and meiosis II of father
B)nondisjunction in meiosis II of mother
C)nondisjunction in either meiosis I or meiosis II of the mother
D)nondisjunction in meiosis I of mother
E)nondisjunction in meiosis II of father

Question 38

Which of the following is not a tenant of the Lyon hypothesis?

A)X inactivation occurs early in development.
B)X inactivation is passed down during mitosis.
C)initial X inactivation is random.
D)X inactivation of descendant cells is the same as the progenitor cell.
E)X inactivation occurs on the maternal X chromosome.

Question 39

In Drosophila,sex is determined by a balance between the number of haploid sets of autosomes and the number of ______.

A)centromeres
B)telomeres
C)X chromosomes
D)nucleolar organizers
E)Y chromosomes

Question 40

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 .

A)female; male; male
B)male; male; female
C)female; male; female
D)male; female; female
E)male; male; male

Question 41

Genotypic sex determination does not in____ .

A)mammals
B)birds
C)reptiles
D)round worms
E)flies

Question 42

In Drosophila,the female is the ____ sex.

A)isogametic
B)heterogametic
C)homogametic
D)mosaic
E)genic balance

Question 43

Data produced by C.Bridges in the early part of this century indicate that sex in Drosophila is determined by__________ .

A)a balance between the number of X chromosomes and the number of haploid sets of autosomes
B)the ratio of X to Y chromosomes
C)the number of X chromosomes
D)the number of Y chromosomes
E)the SRY gene

Question 44

In Drosophila,the sex of a fly with the karyotype____ is male.

A)XX:2A
B)XXY:2A
C)XO:2A
D)XYY:4A
E)XXX:2A

Question 45

In ____,sex is determined by the ratio of the number of X chromosomes to the number of haploid sets of autosomes.

A)humans
B)Drosophila
C)C)elegans
D)reptiles
E)Drosophila and C.elegans