U2T6 - Population Genetics Flashcards
Population Genetics
What are the conditions of the Hardy-Weinberg Principle?
Large population, random mating, no mutations, all genotypes equally fertile (no selection), generations don’t overlap, no emigration/immigration, diploid individuals + no differential selection.
What is the basis of evolution?
When alleles confer advantages to a group and its frequency increases through subsequent generations.
What is necessary for a population to adapt to changing conditions?
Variation must be present. Comes in alleles that gene pool contains. Without these, all individuals look exactly the same.
What are some of the sources of variation that shuffle?
Heterozygotes, alleles, meiosis + cross fertilisation.
Why are heterozygotes a source of variation?
Carry 2 versions of an allele so when reproduce, pass each version on to next gen.
Why is meiosis a source of variation?
Independent assortment of chromosomes during metaphase 1 + crossing over of maternal + paternal sections of chromosomes during prophase 1. IA has potential to create lots of variation in humans as 23 pairs of chromosomes. Num of diff mat + pat chromsomes is 2 to the power of 23!!
Why is cross fertilisation a source of variation?
Gametes fuse randomly so any sperm meets any egg. All offspring genetically diff from each other + parents.
Describe the directional selection of the development of antibiotic resistance by bacteria.
In large pop of bacteria species, some may carry gene for antibiotic resistance. When antibiotic taken by patient with bacteria, most of pop killed off. Resistant bacteria proper + create future pop, all of which are resistant so genome changed abruptly.
Give an example of heterozygous advantage.
Sickle Cell Anaemia. Homozygous HbsHbs - Bad anaemia/death.
Homozygous HbAHbA - No anaemia, susceptible to malaria.
Heterozygous HbAHbS - Mild Anaemia, malaria resistant.
Give 2 methods of speciation by isolation.
Geographic isolation by barriers, restricts movement + breeding.
Reproductive isolation, prevent interbreeding between members of small, isolated pops that have genetically diverged due to isolation.
Allopathic Speciation
Occurs due to geographical isolation (rivers, mountains).
Discuss a model for geographical isolation (allopathic speciation).
Interbreeding pop of 1 species. Pop divided by physical barrier (migration or disaster) If 2 environments different, diff pops experience diff selection pressures + evolve separately. Even if environments similar, pops change by random genetic drift, especially if small pop. Even if barrier removed + pops meet again, now so different they can’t interbreed. Reproductively isolated, 2 distinct species.
What are the reproductive isolating mechanisms?
Temporal isolation, barriers to reproductive process, behavioural isolation, gamete incompatibility + ecological isolation.
What are the barriers before mating?
Geographical separation, habitat isolation + temporal isolation.
What are the barriers after mating?
Gametal incompatibility, non-viable hybrid + hybrid sterility.
