lec 13- the way of change, drift and selection Flashcards
what does the Ester gene in mosquitoes produce?
the enzyme esterase , which is used to detoxify compounds
what were mosquitoes resistant to pesticides found to have?
-mutant allele, called Ester1 which produces much larger quantities of esterase than wild type
-ester provides resistances to pesticides (beneficial mutation)
how did the population of mosquitoes change in two years when they were exposed to pesticides? was the HWE supported or disrupted?
-the mosquitoes carried 100% ester1 alleles rather than normal alleles
-the mosquitoes had evolved (microevolution)
-disrupted
who studied mutations and selections by using E. Coli?
Richard Lenski 1988
how did Richard Lenski test mutations in E coli?
-had 12 populations of E coli that are genetically identical in 12 flasks
- each morning the flasks get new supply of glucose, in the afternoon it runs out
-next day, small sample of survivors from all 12 flasks are transferred to new flasks
-samples from the new flasks were frozen for later study every 500 generations
-all 12 populations increased their fitness in low glucose medium
what is genetic drift?
changes in alleles resulting from random sampling errors or events
when are sampling errors higher?
when populations are smaller
how does genetic drift decrease variation in small populations?
-it randomly changes the alleles in a population, while some alleles are more common and other not so much
-if one allele goes to 0, another allele goes to 1.0 (fixation)
-this can cause the overall loss of an allele in the gene pool which reduces the genetic diversity of the population
are allele frequencies more stable in larger populations?
yes
are rare alleles most likely to be lost in small populations?
yes (p = 0.01, so p + q = 1, alternate allele q is the most common, q = 0.99)
explain the genetic drift experiment of Drosophila that show incomplete dominance in alleles?
bw/bw - white eyes
bw75/bw = orange eyes
bw75/bw75 = red eyes
-start of with 16 heterozygotes (8 M, 8 F), then they randomly breed and a random 8 of each sex are chosen and bred again
-the geneotype and allele frequencies changed by genetic drift in 19 generations, allele loss and fixation clear
-become fixed for one allele, and lose another allele
what are bottlenecks and what do they reduce?
bottlenecks are population crashes and they reduce genetic variation due to drift
how many bottleneck events have cheetahs experienced?
2, one around the 100,000 years ago and the other 10,000 years ago
What have the two bottleneck events caused in cheetah populations?
high inbreeding and genetic drift resulting in high homozygosity (same variant of alleles from both parents)
-found out about homozygosity from skin grafts
what is founders affect?
when a small group of individuals establish a new population, it leads to reduced genetic diversity
were founders prone to genetic drift?
yes
is drift similar to the founders effect?
yes because they both change the allele frequencies
what were the Norfolk island people so prone to migraine?
due to genetic drift and small populations which limited gene pool
are small populations more prone to rare phenotypes?
yes, due to genetic drift
what is inbreeding?
reproduction in a population of close relatives
what does inbreeding have the same consequences as?
as founders effect and genetic drift which reduces gene variation and fixation/loss of alleles
who were the Hapsburg family and what physical issues did they have?
a spanish royal family that inbred a lot resulting in kings dying young and experiencing protruding jaws with swollen tongues
at what age did king Charles II of Spain die?
39
what is inbreeding depression?
when offspring of related individuals have a reduced ability to survive and reproduce
is natural selection effective in large populations?
yes, beneficial alleles may not increase in small populations and can go extinct
what is pleiotropy?
a gene that has multiple phenotypic expressions, can be antagonistic for one trait (negative pleiotropy) and positive for another
what is the positive and negative pleiotropy of a stickleback?
bony plate protect from predators but also affect lateral line sensors used in predator detection
what gene is involved in the production of bony plates in sticklebacks and what genotypes cause low and high armour?
Eda gene, EE causes high armour and ee causes low armour
which type of armour is more common in sticklebacks and why?
low armour because it helps grow faster, survive winter better, and breed better due to less energy needed for them and can be allocated
what are the three main modes of selection?
directional, stabilizing, and disruptive selection
