Chapter 4: Sex Determination

Question 1

What is the difference between sex chromosomes vs autosomes?

Answer 1

Sex chromosomes: Chromosomes that differ between males and female

Autosomes: chromosomes that are the same for male and female

Question 2

What determines male vs female?

Answer 2

Females make larger gametes

Males male smaller gametes

Question 3

What is the sex determination for grasshoppers?

Answer 3

XX-X0 system

1. Females have 2X chromosome, are homogametic
2. Males have one X chromosome, are heterogametic

Question 4

How do the XY chromosomes separate during anaphase if their size is very different?

Answer 4

Question 5

What is genic sex determination?

Answer 5

No obvious differences in chromosomes between males and female. Genotype at one or more loci determine sex

System found in some plants, fungi, protozoans, and fish

Question 6

Who uses the ZZ-ZW sex determination?

Answer 6

Chicken, birds, snakes, butterflies, amphibians and some fish

Female: ZW (heterogametic)

Male: ZZ (homogametic)

Question 7

What are the two types on environmental sex determination?

Answer 7

1. Temperature-dependent sex determination
2. Sequential hermaphroditism

Question 8

How many chromosomes does a diploid Drosophila have?

Answer 8

6 autosomes and 2 sex chromosomes

• Sex determined by balance of female-determining genes on X and male-determining genes on the autosome
• Divide # of X chromosomes by # of complete set of autosomes
• female if above 1 and male if below .5

Question 9

What determines maleness in humans?

Answer 9

Presence of SRY gene on Y chromosome

Question 10

What is

XO

XXY

XXX

XYY

Answer 10

Turner syndrome

Klinefelter syndrome

Poly X female

XYY syndrome (Jacob’s syndrome)

Question 11

What is responsible for non-traditional number of chromosomes?

Answer 11

Nondisjunction

Question 12

What type of non-disjunction occurs during meiosis I

2n=2

Answer 12

Question 13

What type of non-disjunction occurs during meiosis II

2n=2

Answer 13

Question 14

What does more than 3 X chromosomes cause

Answer 14

Physical and mental problems

Question 15

Will the SRY gene be found in

1. XX male
2. XY female

Answer 15

1. Yes
2. No

Question 16

What is Androgen-Insensitivity syndrome?

Answer 16

XY individuals that have testes and produce testosterone, but have a defective androgen receptor

Range of phenotypes: inability to make sperm to development of female secondary sexual characteristics

Androgen receptor is on the X chromosomes so it is inherited from mothers

Question 17

What is dosage compensation?

Answer 17

Equalizes the amount of protein produced by the X chromosome in males vs females

Females inactivate an X and condense it to form Barr body