EE6 Flashcards
What is sexual dimorphism?
phenotypic differences in sexes of species
What is Batemans Principle?
Variance in reproductive success is generally greater in males than in females. Consequence of anisogamy. (fusion of disimilar gametes)
What is Trivers theory of parental investment?
females invest more - compete for resources
males invest less - compete for females
females are therefore more choosy
What did the interbirth interval correlate with the !Kung Tribe?
If IBI is less than 4 years more infants died as mother cant care for new born and young.
What is Fishers runway selection hypothesis?
females mate with attractive males and make attractive sons.
genes for male trait and female preference become associated and magnify over time
natural selection halts process when all males have traitss
What is Zahavais handicap principle?
exagerated secondary sexual traits are a good indicator of good genes. Low quality males can’t fake signal because not strong enough to over come handicap
What is the sexual selection hypothesis reguarding MHC?
Females should prefer males hat produce favourable MHC genotypes for offspring.
Requires female to know MHC type of self and potential ,mate.
females want to max heterozygosity of offspring
What is dissortative mating?
3 examples
Mating of individuals having traits more dissimilar than likely in random mating.
eg. mice have MHC dissortative mating based on odour.s
eg. cycling woman prefer scent of MHC dissimilar men as opposed to woman on the pill.
What conclusions have been drawn from studying MHC sexual selection?
- sharing MHC alleles increases time to conception
- woman are less sexually responsive to men with similar MHC genes
- female preference changes across menstral cycle.
What is the MHC complex and where is it found and what is it responsible for?
most variable region of genome.
encodes immune system proteins
3.6mb region on short arm of chromosome 6
responsible for transplant rejection.
What is the function of the MHC?
recognise foreign polypeptides
bind foreign fragments derived from pathogens and display them on cell surface for recognition by T cells
What are the 2 classes of MHC?
Class 1:
occurs on all nucleated cells. (eg. not rbc)
helps mediate cellular immunity
can only hold short PPs
Class 2:
conditionally expressed by all cell types but normally only occurs on official antigen presenting cells- macrophage, B cells etc.
take up antigen, process and return molecular fragment-epitope to APC - antigen presenting cell
