Sex determination Flashcards
what is an autosome?
nonsex chromosomes, same in males and females
how do the X and Y chromosomes pair?
pairing occurs at the pseudoautosomal regions, in humans the tips of the X and Y chromosomes. these are the only homologous regions of the X and Y
sex vs gender
sex is the sexual phenotype, male or female. gender is not the same, it’s more of a cultural social thing.
monoecious vs dioecious
monoecious: both male and female reproductive structures in the same organism
dioecious: either male or female reproductive structures
mechanisms of sex determination?
chromosomal: XX-XO, XX-XY, ZZ-ZW, haplodiploidy
genic: no obvious difference in chromosomes, only sex genes at one or more loci determine sex
environmental: location, temperature, etc. reptiles, invertebrates, etc
heterogametic
produce two different types of gametes XY
homogametic
produce gametes that are all the same sex chromosomes XX
What did TH Morgan work with? what did he discover?
mutant fruit flies that confirmed the Chromosomal Theory of Inheritance (sex linked traits)
does an XY always develop a male phenotype?
no. androgen insensitivity syndrome creates the female phenotype. cells don’t respond to testosterone and develop female.
Turner syndrome
XO female, missing an X. normal intelligence, short stature, webbed neck, infertility
Triple X syndrome
extra X. not very detectable, tall and fertile
Klinefelter syndrome
XXY male (up to 3 extra X). not very detectable, partial breast development, wide hips, infertile
Supermales
XYY. severe acne, tall, not very detectable, high testosterone levels (?)
how can individuals end up with too many or too few sex chromosomes?
nondisjunction. the X chromosomes fail to separate in meiosis
X linked traits vs Y linked traits inheritance patterns
X linked dominant disorders are equally likely in males and females, while recessives are more likely in males. Y linked traits are only in males and can be used as genetic markers.
