Sex Determination & Sex Linkage - Lecture 12

Question 1

Why are pseudoautosomal regions needed?

Answer 1

○ Shared between the X and Y
○ Required for X-Y pairing in male meiosis

Question 2

What are the sex determinations in mammals?

Answer 2

○ XX = Females
○ XY = Males
○ XO = Females
○ XXY = Males

Question 3

What gene defines an individual as male?

Answer 3

SRY gene

Question 4

What are sterile males?

Answer 4

Translocation of SRY to the X chromosome is found in rare XX males

Question 5

What gives rise to XY females?

Answer 5

Mutation of the SRY gene

Question 6

How does SRY work?

Answer 6

○ A transcription factor
○ When turned on: formation of testis

Question 7

What is the sex determination in birds?

Answer 7

○ ZW = Females
○ ZZ = Males

Question 8

What is gynandromorph?

Answer 8

○ Cells on the right side of the body have the female sex chromosome set
○ Cells on the left side of the body have male sex chromosome set

Question 9

How did the Y and W chromosome evolve?

Answer 9

○ From different autosomes
○ One of the autosomes acquires sex determining locus
○ Accumulates male advantage genes
○ Mutation and deletion

Question 10

What are the facts of sex-linked inheritance?

Answer 10

○ Usually involves genes located on the X chromosome
○ There are also Y-linked genes like spermatogenesis but make up a small %
○ Most genes on X are unrelated to sex determination
○ Males are hemizygous for genes on the X chromosome

Question 11

What is a barr body?

Answer 11

○ Highly condensed X chromosome
○ Happens in females