midterm review Flashcards
define * Population Genetics
this branch of genetics uses knowledge of the rules of inheritance to predict how the genetic composition of a population will change under the forces of evolution and compares the predictions to relevant data
Define Epistasis
Epistasis: a phenomenon where the expression of one gene is modified: masked, inhibited, or suppressed, by the expression of one or more other genes
D Eugenics
Eugenics is the scientifically incorrect and immoral theory of racial improvement and planned breeding - theory that humans can be improved through selective breeding of populations
D Epigenetics
Epigenetics - study of how your behaviors and environment can cause changes to the functionality of your genes
D Balanced Polymorphism
A system of genes in which 2 alleles are maintained in stable equilibrium because the heterozygote is more fit than either of the homozygotes
Who are the leaders of the Modern Synthesis in the field of population genetics?
Main founders: Mendel, Galton, Darwin
3- Who are the leaders of classical Population genetics?
○ R.A Fisher
○ J.B.S Haldane
Sewall Wright
What was R. Fisher famous for?
Balanced polymorphism
What was J.B.S. Haldane famous for?
○ Genetic linkage in mammals
○ Suggested traits can be evolved by natural selection that are detrimental to the population
○ Specific population able to survive due to natural selection and adaptations
6- What was S. Wright famous for?
○ Founder of population genetics
○ The four major factors of evolution
○ Mutation: the author of variation
○ Natural selection: the editor
○ Genetic drift: the randomizer
○ Gene flow: the homogenizer
Describe probability
○ The probability of an event is the relative frequency of that event when the experiment is repeated a large number of times
○ The probability of an event is between 0 and 1
○ The sum of the probabilities of all possible outcomes of an experiment MUST equal 1
○ The probability that something will NOT OCCUR is 1 MINUS the probability that it will occur
different ways of calculating the probability
○ Law of addition
○ The probability that either of two events will occur is the sum of their individual probabilities
○ If A and B are mutually exclusive (cannot happen simultaneously)
- p(A or B) = P(A) + P(B)
Law of multiplication
the prob that both of two independent events will occur is the product of their individual probs
P(A AND B) = P(A) x P(B)
What does the Hardy-Weinberg equation solve?
○ Genotype frequencies if the population is not evolving
What does the Hardy-Weinberg equilibrium explain?
if evolution is occuring - if in HW, it is not
How would the relation between genotype frequencies be explained for a single locus with two alleles (on a graph)? look at it
- Nonnlinear relationship between between allele frequencies and genotype frequencies
○ As p increases, the proportion of homozygous genotype AA increases geometrically, and the frequency of homozygous genotype aa decreases geometrically
○ The frequency of hetero increases as p increase to reach a max at p=0.5 after which the freq of heterozygotes decreases
. What are the assumptions of Hardy-Weinberg Equilibrium?
And what does equilibrium indicate?
■ Sexually reproducing species
- One male, one female
■ Each generation doesn’t overlap
- No one from current generation will not mate with next generation
■ Random mating
- Within same generation
■ No mutation
- No evolution/microevolution
■ No genetic drift
■ No natural selection
■ No gene flow
- Organisms are assumed do not move from one place to another
When would you use the Chi-square?
○ To see how likely it is to get differences between expected and observed genotype numbers that large - if its stat sig
How would the H-W-E equation differ for three alleles
compared to two?
(P + q + r) 2 = 1
Define inbreeding.
○ inbreeding, the mating of individuals or organisms that are closely related through common ancestry
Is inbreeding considered an evolutionary force? Explain your answer.
○ No, it increases homozygosity and decreases heterozygosity but does not really change anything generationally
What does inbreeding affect (genotype or allele frequencies)? Explain.
○ Indirect effect on allele freq
○ Direct effect on genotypes - increases homo decreases hetero
Give an example from the animal kingdom on the effect of inbreeding.
○ white tiger ex
Most white tigers are the result of inbreeding - lots of genetic issues
Who described the inbreeding coefficient?
Wright
. - Define the inbreeding coefficient.
A statistic to estimate the level of inbreeding - how to calculate the inbreeding coefficient
- Give examples from history about inbreeding.
○ King tut
Hapsburg family
- What is the difference between identity by descent and identity by state?
○ The probability that two alleles in an individual were both descended from a single allele in an ancestor (identical by descent IBD)
§ A measure of the level of inbreeding
§ Identity by descent - two alleles the same bc both inherited from a common ancestor (not always the case)
§ The coefficient is F
○ Identical by state - occurs when the identical alleles do not come from common ancestor, they just happen to be the same
Define effective population size.
The breeding population size in an idealized population where a number of conditions (such as equal sex ratio and constancy in population size) apply
- Define fitness.
The probability of an individual with a given genotype surviving and reproducing
Briefly describe the effect of inbreeding on dogs with examples.
○ Dogs have between 2-3% higher genetic load than grey wolves - pattern driven by poor natural selection/inbreeding
○ Also has to do with bottleneck
○ Still being studied
Small population size during domestication and strong artificial selection for breed-defining traits has unintentionally increased the number of deleterious genetic variants (inbreeding depression)
english bulldog ex
○ English bulldog
○ Many large regions of the bulldog genome have been altered to change its appearance
○ Significant loss of variation
○ Loss of the genes that regulate immune responses
○ One of the most popular dog breeds - even as a purebred
Define inbreeding depression
- Inbreeding depression
- The reduced survival and fertility of offspring of related individuals
- The amount of inbreeding depression varies for different individuals, populations, and species
Define genetic rescue
“introduction of beneficial variation from outside the population at
genes which are fixed for (or have a high frequency of) variants
causing inbreeding depression in the population”
what is the word clinicians use when they refer to mutations to avoid incorrect assumptions of Pathogenicity?
§ clinicians are utilizing the word ‘variant’ to avoid the incorrect assumption of pathogenicity as a result of a change in a gene.
Not all mutations are associated with diseases
State different types of mutations and explain each.
- Point mutation:
○ Pyrimidine to pyrimidine or purine to purine (transition)
○ Pyrimidine to purine (transversion)
○ Silent mutations: result in the same amino acid
○ Nonsense- can be a truncated protein if the code is changed to a stop codon
○ Missense - the substitution of the base pair results in a different amino acid
§ Conservative: no change in the function
§ Non-conservative: change in the function
* Frameshift mutations:
○ Insertions and deletions (indel)
○ Causes a shift in the whole reading frame for producing a specific protein- Chromosomal mutations:
○ When a whole segment is deleted, translocated, duplicated, or inverted
- Chromosomal mutations:
Why would species vary in their rate of molecular evolution?
Molecular evolution can vary depending on species body size, pop dynamics, lifestyles, and locations
State three points regarding mutations (including how important they are, where they need to be to pass to the next generation, and whether they are random concerning evolutionary significance?)
○ Mutations occur at random
○ Have to occur in germline/gametes to be passed down
○ Create variety - can be an evolutionary force, main force for genetic variation
5- What are neutral mutations?
○ A mutation whose fixation is independent of natural selection is termed a neutral mutation. Therefore selective neutrality of a mutation can be defined by independence of its fixation from natural selection.
mutations in which natural selection does not affect the spread of the mutation in a species are termed neutral mutations.
- What is the difference between germline mutations and somatic mutations?
○ Germline mutations- occur in gametes, passed down genetically
Somatic mutations - occur in somatic cells and not passed on to offspring
