Deck 4: Sex Determination and Sex Chromosomes

Question 1

A human individual has a karyotype that is XY but is phenotypically female.An explanation for this could be

A) a deletion of the Sry gene on the Y chromosome, thus resulting in an female phenotype.
B) a translocation of the Sry gene to one of the X chromosomes has occurred, thus resulting in a female phenotype.
C) the Sry gene has been amplified 10 fold on the Y chromosome.
D) sex is determined by genes located on autosomes, not sex chromosomes.

Answer 1

A

Question 2

What gene is most responsible for X-inactivation?

A) Xic
B) Xist
C) TsiX
D) Xce

Answer 2

B

Question 3

In a Z-W system,which is considered to be the homogametic sex?

A) males
B) females

Answer 3

A

Question 4

The genetic control of X-inactivation is governed by a short region on the X chromosome called the ________.

A) Y-inactivation center (Yic)
B) condensation center
C) X-inactivation center (Xic)
D) X-initiation center

Question 5

Who originally identified a highly condensed structure in the interphase of nuclei?

A) Lyon
B) Barr and Bertram
C) Ohno

Question 6

Sex determination in humans and Drosophila is similar in the fact that

A) the ratio of X chromosomes to sets of autosomes determines maleness or femaleness in both.
B) males in both will always have one Y chromosome, whereas females will not have a Y chromosome.
C) females lack X chromosomes.
D) males have one X chromosome and females have two X chromosomes.

Question 7

The first person to experimentally determine that a trait is located on a specific chromosome was ________.

A) Mendel
B) Boveri and Sutton
C) Weissman
D) Morgan and Bridges

Question 8

What gene is encoded in the Xic?

A) Xce
B) Xist
C) TsiX

Question 9

Dosage compensation offsets the problems associated with differences in the number of ________ chromosomes in many species.

A) sex
B) autosome
C) somatic
D) nuclear

Question 10

An example of a mechanism in which sex is determined by environmental factors is

A) females are produced from fertilized eggs, whereas males are produced from unfertilized eggs.
B) when the male cares for the eggs, all of the offspring will be male, whereas if the female cares for the eggs, all of the offspring will be female.
C) fertilized eggs incubated at one temperature produce males, whereas eggs incubated at a different temperature produce females. 
D) males will have a Y chromosome, whereas females will not have a Y chromosome.

Question 11

If a gene is located on the X chromosome,but not the Y,it is said to be an example of ________.

A) autosomal inheritance
B) sex-linkage
C) reciprocal cross
D) pseudoautosomal inheritance
E) holandric

Question 12

A male that is produced from an unfertilized haploid egg is an example of what type of sex determination system?

A) X-Y
B) Z-W
C) X-O
D) haplo-diploid

Question 13

In humans,which sex is considered to be the heterogametic sex?

A) male
B) female

Question 14

During sexual reproduction,each parent contributes one set of chromosomes.Similar chromosomes from each parent are called ________.

A) karyotypes
B) sister chromatids
C) homologues
D) sex chromosomes

Question 15

The coat color of calico cats is a result of ________.

A) maternal inheritance
B) X-inactivation
C) imprinting
D) extra nuclear inheritance

Question 16

How many Barr bodies would an individual with a XXY genotype possess?

A) 0
B) 1
C) 2

Question 17

A testcross

A) is used to determine if an organism that is displaying a recessive trait is heterozygous or homozygous for that trait.
B) results in the F2 generation having a phenotypic ratio of 1/2 dominant to 1/2 recessive.
C) is used when an individual with a dominant phenotype and unknown genotype is crossed to an individual with a recessive phenotype.
D) results in offspring that always display the recessive phenotype.

Question 18

The Lyon hypothesis attempts to explain the molecular mechanism of ________.

A) X-inactivation
B) genomic imprinting
C) maternal inheritance
D) extra nuclear inheritance

Question 19

Which of the following does not inactivate an X chromosome?

A) mammals
B) Drosophila
C) C. elegans
D) humans

Question 20

Studies of X-linked inheritance and sex chromosomes provided the evidence for which of the following?

A) chromosomal theory of inheritance
B) particulate theory of inheritance
C) theory of natural selection
D) law of segregation
E) principle of dominance

Question 21

With rare exceptions,a calico cat is likely to be female.

Question 22

Red-green colorblindness is a X-linked recessive trait in humans.If a woman who is a carrier for red-green colorblindness marries a normal male,what percent of their sons will be colorblind?

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

Question 23

Pseudoautosomal inheritance occurs when

A) a gene on an autosome is silenced by inactivation.
B) a gene on a Y chromosome has the same inheritance pattern as a gene on an X chromosome.
C) a gene on an autosome has the same inheritance pattern as a gene on a sex chromosome.
D) a gene on a sex chromosome has the same inheritance pattern as a gene on an autosome.

Question 24

Brown spotting of the teeth in humans is caused by a dominant X-linked gene. If a man with normal teeth marries a woman with brown teeth who had a father with normal teeth,then ________ of their daughters will have brown teeth.

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

Question 25

Flowering plants will produce flowers that are dioecious,meaning that the male and female parts are contained within the same flower.