Genomics week 7

winniesmith2's version from 2018-01-11 13:19

Section 1

Question Answer
What are mutations-Primary source of genetic variation! Mutation rates can generate a lot of potential variation in a population - 7 billion humans would produce about 14 billion new alleles per generation.
What are mutation rates very low - about 10-6 (1 in a million) for a gene, 10-9 (1 in a billion) for a particular base pair in DNA
The overall number of mutation is low, why?-Repair mechanisms and repair enzymes.
-Mutations can be Forward (AB allele) or Backward (BA) maintaining balance and only small, slow change to allele frequencies in the population.
-Unless mutation rates are abnormally high, the change in p and q are virtually nil.
-No major effect on HWE.
-only if you have radiation disaster will allele frequencies drastically change.
Mutations, why do they only have a small effect?Mutation rates are very low-
at a rate called mu. Mathematically, q will now be equal to that fraction of p that mutated.
This calculation also does not even take into account back mutations.
how long does it take a mutation to become a polymorphism needs to been seen in 1% of the population. takes many generations to occur, and the mutation needs to be passed to offspring.
what is mutation NOTNOT the primary reason for departure from HWE. that would be genetic drift and migration.

Section 2

Question Answer
What is differential reproductionthose individuals best able to survive and reproduce will do so more often than others
What is selection based on differences in fitness. Fitness refers to the ability to survive and produce offspring (pass on genes). Fitness is a measure of offspring produced.
How can alleles/genotypes effect fitnessCertain alleles can increase or decrease fitness. These effects can be dominant, recessive, co-dominant or additive. Whether an allele is selective will also depend on the genetic background (other genes) and environment.
What is fitnessthe number of offspring an individual produces that survive to reproduce themselves.
What does it mean if fitness=1.0means that individuals of this phenotype are successfully passing on 100% of their genes, on average
Natural selection will not take place ifthere is no variation,
if the gene is not heritable,
if there is no difference in survivorship or reproductive ability between variants.
'Survival of the fittest' This saying is a bit misleading and doesn’t quite capture the essence of what is natural selection. You can be as “fit” an individual as can be but it is the ability to reproduce that is the key feature for an increase in representation in the next generation
What is darwinian fitness the average number of offspring left by a genotype
What is relative fitness (w)calculates fitness in relation to the most fit genotype
What is the selection coefficient (another way to look at fitness) the amount of selection against a genotype. With a difference in fitness, each genotype no longer has an equal likelihood of contributing to the gene pool of the next generation. The contribution to the next generation is a result of frequency times fitness. ex. pg 13
What is the heterozygote advantage Way for selection to maintain a stable equilibrium with polymorphism -BOTH alleles selected for -Heterozygote more fit than either homozygote -eg. Sickle cell anemia