ch 7: sex determination and sex chromosomes

Question 1

heteromorphic chromosomes

Answer 1

XY

Question 2

mosaics

Answer 2

somatic cells show two different genetics lines

Question 3

primary sexual differentiation

Answer 3

only gonads where gametes produced

Question 4

secondary sexual differentiation

Answer 4

overall phenotype of organism, clear differences in organs like mammary glands and external genitalia

Question 5

Pseudoautosomal regions (PARs)

Answer 5

share homology with regions on X chromosome-meiosis

Question 6

Male-specific region of the Y (MSY)

Answer 6

non recombining region of Y, still some homology with X

Question 7

Sex-determining region Y (SRY)

Answer 7

critical gene controlling male development (includes TDF)

Question 8

Testis-determining factor (TDF)

Answer 8

transcription factor

Question 9

heterochromatic

Answer 9

regions lacking genes

Question 10

Paternal Age Effects (PAE)

Answer 10

paternal age associated with increased risk of congenital disorders with genetic basis

Question 11

primary sex ratio

Answer 11

proportion of males to females conceived in population

Question 12

secondary sex ratio

Answer 12

proportion of each sex that is born
-easier to measure, but doesn’t account for the disproportionate embryonic or fetal mortality

Question 13

dosage compensation

Answer 13

always 2 of all chromosomes, except sex chromosomes, males hemizygous

Question 14

barr body

Answer 14

-number of inactive X chromosomes
highly condensed structure lies against nuclear envelope of interphase cells and stains positively using DNA dyes

Question 15

number of Barr bodies

Answer 15

=N-1
(N being the total number of X chromosomes present)

Question 16

lyon hypothesis

Answer 16

inactivation of X chromosome occurs randomly in somatic cells early in embryonic development
-once inactivation occurs, all descendant cells have same X chromosome inactivated

Question 17

imprinting

Answer 17

• gene from one parent is expressed while the other parents is silenced
• EX: brown and blue eyed parents with brown eyes child

Question 18

X-inactivation center (Xic)

Answer 18

major control region on X chromosome, genetic expression occurs only on the chromosome which is inactivated

Question 19

XIST

Answer 19

-part of Xic that is a long noncoding RNA
-recruits a protein complex that silences transcription at epigenetic level by spreading over and coating X chromosome to be inactivated

Question 20

hermaphrodite

Answer 20

contains testes and ovaries
-can self-fertilize
-ratio of X to autosome still determines sex

Question 21

temperature-dependent sex determination (TSD)

Answer 21

sex determined by incubation temperature of eggs during stage of embryonic development

Question 22

extrachromosomal inheritance

Answer 22

influenced by the parent contributing the most cytoplasm to the embryo
-dont follow typical mendelian patterns