BISC 200: Sex Determination and Sex Chromosomes

Exam 2

sexual dimorphism

shape, size, and structure of chromosomes

sex determination

the genes on sex chromosomes is what determines the sexual phenotype

acrocentric

centromere is near the end of a chromosome

heterogametic

males produce different gametes

homogametic

females produce the same gametes

pseudo autosomal regions

regions at the tip of chromosomes that allow for genetic recombination

male specific region of the Y (MSY)

95% of the Y chromosome that doesn’t synapse (undergo genetic recombination)

euchromatic

contains most of the genes; involved in transcription

heterochromatic

remains condensed; mostly genetically inactive

what and where is the sex-determining region of Y (SRY)

determines sex; located under PAR (pseudo autosomal region)

genic sex-determining systems

sexual phenotype determined by genes at one or more loci (no sex chromosomes)

the Y chromosome is divided equally with what material?

euchromatic and heterochromatic material

Turner Syndrome

45, X

Klinefelter Syndrome

47, XXY

Poly-X females

47, XXX

Jacob’s Syndrome

47, XYY

How can an individual have two X chromosomes and phenotypically be a man.

only part of the Y chromosome needs to be present (mostly seen when SRY gene is present on the X chromosome)

primary sex ratio

males to females conceived in a population

secondary sex ratio

number of each sex that’s born