Chapter 4.2: Sex Chromosomes and Sex Determination

Question 1

What does the sex chromosome genotype XXX produce in drosophilia?

Answer 1

dies

Question 2

When is amniocentesis performed?

Answer 2

 Performed approximately 16 weeks after woman’s last menstrual period

Question 3

What does the sex chromosome genotype OY produce in drosophilia?

Answer 3

dies

Question 4

What does the sex chromosome genotype XO produce in drosophilia?

Answer 4

sterile male

Question 5

Define sex chromosomes

Answer 5

two distinct chromosomes that provide the basis of sex determination

Question 6

What does the sex chromosome genotype XX produce in humans?

Answer 6

normal female

Question 7

Define SRY

Answer 7

sex determining region of Y

Question 8

What does the sex chromosome genotype XY produce in humans?

Answer 8

normal male

Question 9

What does the sex chromosome genotype XYY produce in humans?

Answer 9

normal or nearly normal male

Question 10

What are two distinct chromosomes that provide the basis of sex determination?

Answer 10

sex chromosomes

Question 11

What does the sex chromosome genotype XXY produce in humans?

Answer 11

Klinefelter male (sterile); tall, thin

Question 12

Where did evidence of SRY come from?

Answer 12

o Evidence implicating SRY came from sex-reversal: the existence of XX males and XY females

Question 13

What does the sex chromosome genotype XY produce in drosophilia?

Answer 13

normal male

Question 14

What are pseudoautosomal regions (PARs)?

Answer 14

o The two ends of the Y chromosome are called pseudoautosomal regions (PARs), because homologous regions are present at the ends of the X chromosome

Question 15

What is amniocentesis?

Answer 15

o Method to obtain fetal cells whose DNA and chromosomes can be analyzed for genotype

Question 16

What is a o Method to obtain fetal cells whose DNA and chromosomes can be analyzed for genotype?

Answer 16

amniocentesis

Question 17

What does the sex chromosome genotype OY produce in humans?

Answer 17

dies

Question 18

What is the heterogametic sex?

Answer 18

o The sex having two different sex chromosomes is termed the heterogametic sex because it gives rise to two different types of gametes
 These gametes in humans would contain either X or Y

Question 19

What does the sex chromosome genotype XXX produce in humans?

Answer 19

nearly normal male

Question 20

What does the sex chromosome genotype XX produce in drosophilia?

Answer 20

normal female

Question 21

Describe amniocentesis

Answer 21

o Doctor inserts needle through pregnant woman’s abdominal wall into the amniotic sac where fetus is growing
o Use ultrasound imaging to guide needle and withdraw some amniotic fluid
 Fluid contains living cells called amniocytes shed by the fetus
 When placed in a culture medium, these fetal cells undergo mitosis several times and increase in number
o Once enough fetal cells are available, clinicians look at the chromosomes and genes in those cells

Question 22

What does the sex chromosome genotype XYY produce in drosophilia?

Answer 22

normal male

Question 23

What does the sex chromosome genotype XXY produce in drosophilia?

Answer 23

normal female

Question 24

What does the sex chromosome genotype XO produce in humans?

Answer 24

Turner female (sterile); webbed neck