sexing and mating systems Flashcards
what is true of the genotype frequencies in a population in HWE
genotype frequencies have reached a stable condition
why is sex identification important
behavioural and ecological research
breeding and conservation work
what morphological cues can be used for sex ID and what is the issue with this method
external genitalia and secondary sexual characteristics
not all animals are sexually dimorphic
how can sex ID be carried out surgically and what is the issue with this method
incision along abdomen to allow direct examination of internal sex organs
risky for some animals, time-consuming, stressful for animal
how do you carry out cytological sex ID and
what is the issue of cytologically determining sex
examination of the chromosomes in the nucleus to identify sex chromosomes
need to culture cells, field sampling challenging, technique requires expert training
how can DNA fingerprinting be used for sex ID
what is the issue with this method
examine microsatellite, (RAPD or AFLP) polymorphisms to find markers which are sex specific
mutation rate is high as it usually based on polymorphisms of non-coding regions and there are different protocols needed for different species
how can PCR amplification of sex-linked gene be used for sex ID
what are the benefits of this method
what is the issues with this method
DNA sequences of genes tend to be conserved across species
markers based on sex-linked gene more likely to be useful across many species and PCR primers can be specific
not all organisms have sex determined genes
‘universal’ molecular sex ID using PCR is possible for what organisms
mammals and birds
what gene is used in mammals and where is it found
SRY gene on the Y chromosome
what are the sex chromosomes in birds
ZZ (male) and ZW (female)
what gene is used when sexing birds via PCR amplification and what is this method known as
chromosome-helicase-DNA-binding (CHD1) gene
females have CHD1-W and CHD1-Z
males only have CHD1-Z gene
known as ‘Griffiths’ or ‘CHD1’ sexing method
PCR products separated by size with gel electrophoresis, 2 bands for female and 1 band for male
what is Fisher’s sex ration theory
that the optimal and stable primary sex ratio (at fertilisation) must be 50:50
what are 2 assumptions of Fisher’s theory
male and female parents are equally good at producing male and female offspring at all ages
mating is random in a large population
explain how red deer exhibit changing sex ratio in response to environment
male must be large enough to defend harem, size provides reproductive advantage
mother in good condition who can produce large offspring is more likely to produce a male
a mother in poor condition who can only produce small offspring is more likely to produce females
sex with higher reproductive cost is choosy, which sex is this (usually)
females
