Chapter 5: Sex Determination & Sex Chromosomes Flashcards
about how many genes are present in the Y chromosome?
75
about how many genes are present in the X chromosome?
900-1400
pseudoautosomal regions share
homology with regions on X chromosome
the male specific region of the Y chromosome is equally divided between
euchromatic and heterochromatic regions
euchromatic regions are known as
functional genes
heterochromatic regions are known as
lacking genes
the sex determining region of the Y chromosome is a critical in
controlling sexual development
what does SRY stand for?
sex determining region
what does MSY stand for?
male specific region of the Y
what does PAR stand for?
pseudoautosomal region
what does TDF stand for?
testis-determining factor
The SRY gene encodes for what protein?
testis determining factor
a form of dosage compensation are known as
Barr Bodies
what is the lyon hypothesis?
inactivation of X chromosome is random; all descendant cells have same inactivation
mechanisms of X chromosome inactivation include
- DNA or histone proteins
- imprinting
define imprinting
process where expression of genes on one homolog is affected but not the other
in drosophila sex is determined by?
the ratio of X chromosomes to haploid sets of autosomes
describe sex ratios in drosophila
female- 1:1
male- 1:2
genic balance theory states that
- threshold of maleness is reached when X:A ratio is 1:2
- presence of additional XX:A alters balance resulting in female
hermaphrodites have
both testes and ovaries
TSD stands for?
temperature-dependent sex determination
Why is TSD so profound in influencing sex determination?
enzymes are inhibited by temperature
What are the 3 different patterns of TSD in reptiles?
- low temp = 100% females
high temp = 100% males - low temp= 100% males
high temp= 100% females - low and high temp = 100% females
intermediate temps = various proportions of males
