genetics & evolution Flashcards
penetrance
proportion of individuals with an allele that express the phenotype associated with the allele
expressivity
varying phenotypes despite identical genotypes; may be a range of possible phenotypes
Mendel’s first law- of segregation
an organism has two alleles for each gene, one inherited from each parent; if two alleles are different, only dominant will be expressed
law of independent assortment
inheritance of one gene does not affect inheritance of another gene; doesn’t account for linked genes
Griffith study with rough (not virulent) and smooth (virulent/disease causing) pneumonia strains
If inject rough/non-virulent strain– mouse lives
If inject smooth strain– mouse dies
If inject heat killed smooth strain– mouse lives
If inject rough strain and heat-killed smooth strain–mouse dies– transformation: the live, nonvirulent bacteria acquired ability to form smooth capsules from dead, virulent bacteria
Transposons
elements that can insert and remove themselves from the genome; if it inserts into the middle of a coding sequence, will disrupt the gene
Inborn errors of metabolism
mutations that cause defects in genes required for metabolism
genetic leakage
flow of genes between species
genetic drift
changes in the composition of the gene pool due to chance
founder effect
small population of a species ends up in reproductive isolation due to natural barriers or catastrophic events; as a result- inbreeding may occur, causes reduction in genetic diversity
Monohybrid cross
only one trait is being studied
Test cross
used to determine an unknown genotype; unknown genotype is crossed with homozygous recessive organism; if all dominant offspring- it was homozygous dominant, if 1:1 ratio, then it was heterozygous
Dihybrid cross
consider two traits; observe a 9:3:3:1 ratio if cross two heterozygotes; easiest to solve by making two separate punnett squares
sex-linked crosses
Use X and Y to symbolize the chromosomes, subscripts to represent alleles; males only need one recessive allele to express a sex-linked disease
chiasma
point of crossing over during recombination
recombination frequency
likelihood that two alleles will separate from each other during recombination, increases with distance of separation
genetic mapping
one map unit/centimorgan corresponds to 1% chance of recombination occurring between two genes
allele frequency
how often an allele appears in a population; ex. if you had 50 plants, you would have 100 alleles; if 75 of them were dominant, allele frequency= 75/100
Hardy Weinberg Equilibrium conditions
large population size; no mutations in gene pool; random mating within population; no migration into or out of population; genes in pool are equally successful at reproducing
Hardy Weinberg equations for a trait with two alleles, where p is dominant and q is recessive
p+q=1 (where p and q indicate allele frequencies)
p^2 + 2pq +q^2 = 1 (can get equation by squaring top one)
sum of p^2 and 2pq would represent dominant phenotype frequency
modern synthesis model of evolution (neo- Darwinism)
updated form of Darwinism; when mutations occur that are favorable to the organism, the change is likely to be passed on to the next generation; it is the GENE POOL that evolves over time- populations evolve, not individuals
Inclusive fitness
organism’s success in a population, based on number of offspring and ability to support offspring
Altruistic behavior
may threaten an individual’s life, but can improve the success of the population as a whole by helping others
Punctuated equilibrium
pattern of evolutionary change where long periods pass with little change followed by a brief period of rapid change; changes occur in short bursts
