Section 2

Question 1

The sequencing of human chromosomes 21 and 22 showed that

a. some regions of chromosomes do not code for proteins.
b. all of the DNA of chromosomes codes for proteins.
c. different chromosomes have the same number of genes.
d. different chromosomes contain the same number of DNA bases.

Answer 1

a.some regions of chromosomes do not code for proteins.

Question 2

Alleles found on the same chromosomes…

Answer 2

are linked

Question 3

The long stretches of repetitive DNA in chromosomes 21 and 22 are unstable sites

Answer 3

where rearrangements occur.

Question 4

Most sex-linked genes are located on

Answer 4

the X chromosome only *

Question 5

Colorblindness is more common in males than in females because

Answer 5

the allele for colorblindness is recessive and located on the X chromosome.

Question 6

This statement is true

Answer 6

The mother of a colorblind boy must be colorblind.

Question 7

Which of the following form(s) a Barr body?

Answer 7

one of the X chromosomes in a female cell

Question 8

The formation of a Barr body

Answer 8

causes the genes on one of the X chromosomes in a female cell to be switched off.

Question 9

A cat that has spots of only one color

Answer 9

must be a male.

Question 10

The failure of chromosomes to separate during meiosis is called

Answer 10

nondisjunction.

Question 11

Because the X chromosome contains genes that are vital for normal development, no baby has been born

Answer 11

without an X chromosome.

Question 12

Which of the following combinations of sex chromosomes represents a female?

Answer 12

XX

Question 13

If nondisjunction occurs during meiosis,

Answer 13

the chromatids do not separate.*

Question 14

Nondisjunction can involve

Answer 14

homologous chromosomes.

Question 15

Why are sex-linked traits more common in males than in females?

Answer 15

A recessive allele on the X chromosome will always produce the trait in a male.

Question 16

Sex-linked genes are genes on

Answer 16

the X and Y chromosomes.

Question 17

A carrier is a person who has

Answer 17

one recessive and one dominant allele for a trait.

Question 18

What must occur for a girl to be colorblind?

Answer 18

Each parent must be colorblind.

Question 19

Hemophilia is caused by a(n)

Answer 19

recessive allele on the X chromosome.

Question 20

Sex-linked traits that are controlled by recessive alleles are more likely to show up in males

Answer 20

True

Question 21

A boy who has hemophilia inherited the disorder from his

Answer 21

Mother

Question 22

A Barr body is a turned-off ____________________ chromosome.

Answer 22

X

Question 23

A female with the disorder _________________________ inherits only one X chromosome and has the genotype XO.

Answer 23

Turner’s syndrome

Question 24

Nondisjunction in males can lead to the disorder called ______________________________.

Answer 24

Klinefelter’s

Question 25

A person who has the genetic disorder called ____________________ bleeds easily.

Answer 25

Hemophilia

Question 26

Down’s syndrome is caused by the presence of an extra ____________________.

Answer 26

three copies of a chromosome

Question 27

A karyotype can be used to diagnose the genetic disorder called ____________________.

Answer 27

down syndrome

Question 28

A person with Down syndrome has two copies of the 21st chromosome.

Answer 28

False 3

Question 29

Males generally do not have Barr bodies.

Answer 29

true

Question 30

A boy who has hemophilia inherited the disorder from his father.

Answer 30

False mother

Question 31

A female with the disorder Kleinfelter’s syndrome inherits only one X chromosome and has the karyotype 45XO.

Answer 31

true