genetics chapter 4.1

what does meiosis produce?

haploid gametes

what does fertilization produce?

diploid zygote

fertilization

fusion of gametes

3 types of sex determination

1. chromosomal
2. genetic
3. environmental

homogametic sex

2 of the same sex chromosomes (eg XX, ZZ)

heterogametic sex

2 different sex chromosomes (eg XY, ZW)

X chromosome

sex chromosome in both men and women; XX is female

Y chromosome

the sex chromosome found only in males

O chromosome

stands for the abscense of a sex chromosme; commonly found in insects

Haplodiploidy

ploidy level determines sex (fertilized is female, unfertilized is male)

genic sex determination

sex is determined by genes instead of sex chromosomes

environmental sex determination

the environment determines sex of offspring

How does the heterogametic sex differ from the homogametic sex?

gametes of the heterogametic sex have different sex chromosomes; gametes of homogametic sex have the same chromosomes

do X and Y chromosomes cross over?

no

do X and Y chromosomes behave like homologous chromosomes?

yes

Are X chromosomes or Y chromosomes larger and which have more gentic info?

X are larger and have more gentic info

What part of the X and Y chromosomes are homologous?

pseudoautosomal regions

how many pseudoautosomal regions are there and what are they called?

2; primary and secondary

what are pseudoautosomal regions essential for?

pairing in meiosis

What is Turner Syndrome?

Occurs in females when they only have one X chromosome (genotype XO)

What is Klinefelter syndrome?

occurs in males when they have at least one extra X chromosome (XXY genotype)

What is Poly-X Syndrome?

females have an extra X chromosome (XXX genotype)

how many X chromosomes are required for normal human development?

at least one

which chromosome contains genetic info for both sexes?

X

what chromosome is the male determining gene located on?

Y

what does the abscense of a Y chromosome result in?

female phenotype

what chromosomes are genes affecting fertility located on?

X and Y

what is the male determining gene in humans?

SRY gene

what does SRY stand for?

sex determining region of the Y chromosome

what is SRY protein?

a transcription factor that binds to and bends DNA molecules. an alteration may affect the expressin of the other gene that encodes testis development

What is androgen insensitivity syndrome?

male individual (XY) that is phenotypically female. Testes form inside the body and do not function