These notes are a 3-page summary of GTS161 study unit 3. They provide a detailed but concise overview of the lecture notes with colour images to aid understanding. They were written by a student who obtained a distinction in the module.
Theme 3
Sex
•
Hermaphrodi.sm - both sexes in 2. XX-XO determina.on:
same organism § Females (XX) - soma.c cells
• Monoecious - both male and have 2x autosome sets and
female reproduc.ve structures in 2X / haploid cells have one
same organism autosome set and 1X
• Diecious - either male or female chromosome
reproduc.ve structures in one § Males (XO) - soma.c cells
organism have two sets autosomes and
§ Chromosomal, 1X chromosome / sperm
environmental or genic sex have one set autosomes and
determina.on either 1X or no sex
Chromosomal sex determina.on chromosome
• Determined by genes on 3. ZZ - ZW sex determina.on
chromosomes § Females (ZW) - soma.c cells
• sex chromosomes - chromosomes have two sets of autosomes
which differ in number and/or and 1Z or 1W / eggs have one
morphology between males and set of autosomes and 1Z or
females 1W
• Autosomes - the same in males § Males (ZZ) - soma.c cells
and females have two sets of autosomes
• Homogame.c sex - sex that and 2Z / sperm have one set
produces gametes that are all the of autosomes and 1Z
same with respect to the sex Genic sex determina.on
chromosomes • NO sex chromosomes
• Heterogame.c sex - sex that • Genes on autosomes determine
produces two different types of sex
gametes with respect to the sex Environmental sex determina.on
chromosomes • Environmental factors determine
• SRY gene on Y = maleness sex
1. XX-XY determina.on: Drosophila melanogaster
§ Female (XX) - soma.c cells • Sex predicted by X:A ra.o (A -
have two sets of autosomes haploid sets of autosomes)
+ 2X chromosomes / • Y does not determine sex but plays
Haploid eggs - one set if a role in male fer.lity
autosomes and 1X
§ Males (XY) - soma.c cells
have two autosomes sets
and 1X / sperm have one
autosome set and 1X or 1Y
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