Sex determination and sex chromosomes Flashcards
What is phenotypic dimorphism
differentiation of sexes
What is the protenor mode of sex determination
two X chromosomes - female
one X chromosome - male
what is lygaeus mode of sex determination
All female gametes have X (homogametous)
male gametes have either x or y (heterogametous)
What is ZZ/ZW sex determination
females are ZW sex
males are ZZ
Describe Klinefelter syndrome
XXY - male genitalia, more than one X chromosome, wide hips narrow shoulders, poor beard growth, small testicular size
Describe Turner syndrome
a single X chromosome
no y
female genitalia
no menstruation
What are pseudoautosomal regions?
Share homology with regions on the X chromosome and synapse with it
What are MSY and SRY?
MSY - male specific region
SRY - subregion of MSY, sex determining region containing genes required to develop as male, becomes active at 6-8 weeks of development, triggers testes formation
Describe sex differentiation in terms of gonads
gonadal primordia are tissues that form the gonad
gonadial ridges form by fifth week of gestation
biopotential gonads can form either as ovaries or testies
what is dosage compensation?
balances dose of X chromosome gene expression in males and females
extra x in female cells is inactivated through Barr bodies
What is the Lyon Hypothesis
random inactivation of X chromosome causes all descendant cells to have same X inactivation
Describe sex determination in drosophila
if ratio of X chromosomes is greater or equal to 1, female
0.67-1 = intersex
0.33-.5 = male
x inactivation not observed in drosophila
