Sex conflict and cooperation Flashcards
What is sex?
Any genetic exchange between individuals, the occurence of meoisis
What does meoisis involve
Initiated by the fusion of two haploid gametes to form a diploid zygote. Process of recombination of paternal and maternal genomes
What are the costs of sex
Physiological costs of meiosis
Risk of producing maladapted offspring
Cost of mating
Cost of producing males
What does asexual reproduction produce
Its a copying process, produces genetically identical clones
What does recombination allow
Favourable mutations to be integrated more qucikly into the population
What is mullers rachet
Random loss of mutation free chromosomes, population gets worse every generation
What is genetic hitchhiking
Deleterious mutations linked to beneifical ones, beneficial under positive selection, increasing in frequency, deleterious mutation is dragged along
What is ruby in the rubbish
Linkage between strong deleterious mutation and a weakly beneficial one, weak beneficial one will be lost so process of adaptation is slower
What is the Hill Robertson effect
Asexual population, 3 genes, when these beneficial alleles arise, they arise in different individuals. The only way to get the fittest genotype is to wait overtime
What is the benifit of sex
Shuffles the genome to produce new combinations of genes
What are the other hypothesises to why sex is maintained
Advantageous in variable environments, more likely to be an advantage if the environment changes rapidly
What is the co-evolutionary arms race aka red queen hypothesis and what does it lead to
Between parasite and the host. Leads to cycles of adaption and counter adaption
List of evidence for the red queen hypothesis
Sex of new zealand snails, parasite has large fitness consequences
High levels of parasitism favours sexual reproduction
Gibson reviewed that theres a strong correlation between parasitism and outcrossing
What determines sex in male in American alligators
Incubation of eggs, 33 degrees produces males and lower produces females
Who discorred sex chromosomes in the early 1900s
Nettie Stevens
What are the new type of chromosomes
Females have ZW, males have ZZ. Occurs in birds, fish and geckos
What happens when recombination is lost
Deleterious mutations start to accumulate
What does the X chromosome in humans contain compared to Y
1000 genes, Y only encodes 45 proteins
What does gene conversion involve
The transfer of genes from the donor sequence to the acceptor sequence facilitated by the amplionic regions
What are palindrome regions
Mirror image repeat structures
How many palindrome repeats does the Y chromosome have
9
Whats the cycle of sex chromosome evolution
Sex chromosomes -> supression -> divergence -> degeneration -> loss of Y/W -> autosomes ->
What are the two different strategies for gamete production
One really big gamete, or lots of smaller gametes
What is zygote size determined by
The sum of gametes that fuse from it
Which gametes are more likely to survive
The bigger gametes
What does disrputive selection of gamete size act against
Medium gametes as they are mediocre at both functions. Disruptive selection leads to unequal gamete sizes