ch.4 sex determination and sex linked characteristics Flashcards
what are the costs of sexual reproduction?
-can be expensive (energy-wise)
- you do not pass on all of your genes because each offspring only has half of your genes
what are the benefits of sexual reproduction?
- genetic variability
what is the homogametic sex?
gametes that all have the same sex chromosome
(females in humans)
what are pseudoautosomal regions?
regions where you can have cross over between the X and Y chromosomes because they are homologous with each other at that section
- allow for autosomal inheritance
what is the SRY gene and what does it do?
the SRY gene determines maleness (on the Y)
- it is a transcription factor that stimulates the transcription of genes that promote differentiation of testes
- males can have multiple X’s as long as they have this gene
What is androgen insensitivity syndrome?
hormones such as testosterone and anti-mullerian hormone are made but not perceived by the body so male characteristics cannot fully develop
- leads to intersex individuals
What is environmental sex determination?
- sex phenotype is partly or fully determined by environment
- ex. temp - as temps rise there are more female reptiles than males and so females may not be able to find mates
- ex. sequential hermaphroditism - certain larva settles and develops into a female; then as more crawl on top they mate and then turn into females themselves (environmental factor is position on the stack)
what is the XX-XO sex determination systems?
grasshoppers and other insects
- XX = female
- XO = male
what is the XX-XY sex determination system?
Insects, fish, amphibians, reptiles, mammals, and humans
- XX = female
-XY = male
what is the ZZ-ZW sex determination system?
Butterflies, birds, some reptiles and amphibians
ZW = females
ZZ= males
What is hemizygosity?
since diploid males have only 1 X they are hemizygous at x-linked alleles
- one recessive alleles is enough for X linked recessive to show up in males
