lecture 11: sex determination and sex chromosomes

Question 1

only natural mechanism for producing new members in a wide variety of species

Answer 1

sexual reproduction

Question 2

meiosis ensures

Answer 2

genetic constancy

Question 3

Klinefelter syndrome

Answer 3

male (XXY)
testes are rudimentary and fail to produce sperm

Question 4

turner syndrome

Answer 4

female (X)
ovaries rudimentary

Question 5

pseudoautosomal regions (PARs)

Answer 5

present on both ends of Y chromosome
critical for segregation of X and Y chromosomes during male gametogenesis

Question 6

male-specific region of the Y (MSY)

Answer 6

divided equally between euchromatic and heterochromatic regions
*makes up remaining 95% of chromosome

Question 7

sex-determining region Y (SRY)

Answer 7

critical gene controlling sexual development
* absence of this region leads to female development

Question 8

SRY encodes the protein

Answer 8

TDF (testes-determining factor)

Question 9

dosage compensation

Answer 9

one of the X chromosomes that the female is giving is turned off and condensed into a Barr body

Question 10

occurs in the early female embryo, where both the maternal and paternal X chromosome have an equal chance of become inactivated

Answer 10

random X inactivation

Question 11

process whereby expression of genes on one homolog but not other is affected

Answer 11

imprinted X-inactivation

Question 12

lyon hypothesis

Answer 12

which X chromosome becomes inactivated is random (can be maternal or paternal)

Question 13

how many barr bodies in turner syndrome

Answer 13

no Barr bodies (XO)

Question 14

how many barr bodies in klinefelter syndrome

Answer 14

one barr body (XXY)