Flashcards
Genetics and Evolution
Cards in this deck (38)
- 1locuseach gene has a particular locus or location on a specific chromosome,
- 2hemizygous genotypedescribes a situation in which only one allele is present for a given gene as is the case of parts of the X chromosomes in male
- 3complete dominance vs codominancewhen only one dominant and one recessive allele exist for a given gene, in this case the presence of one dominant allele will mask the recessive allele
codominance when more than one dominant allele exists for a given gene - 4incomplete dominanceoccurs when a heterozyogote expresses a phenotype that is intermediate between the two homozygous genotype, example pink
- 5penetrancepopulation measure defined as the proportion of individuals in the population carrying the allele who actually express the phenotype
full penetrance - 100 percent of individuals with this allele show symptoms (more than 40 sequenced repeats for huntington)
High Penetrance - individuals with fewer sequences most butn ot all of those with the allele show symptoms
reduced penetrance , low penetrance or nonpenetrance - 6expressivityvarying phenotypes despite identical genotypes, different manifestation of the same genotype across the population
if expressivity is CONSTANT then all individuals with a given genotype express the same phenotype
however if expressivity is variable then individuals with the same genotype may have different phenotypes - 7expressivity vs penetrancepenetrance is a population parameter (what percent of individuals with a given genotype express the phenotype)
expressivity - is considered more on the individual level, e.g neurofibromatosis type II is an autosomal dominant disease that results from a mutation of a gene NF2 (merlin), a range of phenotypes is associated with carrying the allele, ranges from no clinical effect to severe disability, has a most of the population is penetrant - 8what are the four tenets of Mendel's first law (of segregation)genes exist in alternative forms (alleles)
an organism as two alleles for each gene, one inherited from each parent
the two alleles segregate during meiosis resulting in gametes that carry only one allele for any inherited trait
if two alleles of an organism are differnet only one will be fully expressed and the other will be silent (exceptions are codominant and incomplete dominance)
cellular correlate is the separation of homologous chromosomes during anaphase I of meiosis, by separating/segregating these chromosomes into different cells each gamete carries only one allele for any given trait - 9mendel's second law (independent assortment)states that the inheritance of one gene does not affect the inheritance of another gene, (note this has been problematized by the discovery of linked genes)
during meiosis prophase I homologous chromosomes pair up to form tetrads, which derive their name from the four chromatids involved (two chromatids in each of two homologous chromosomes) - 10gene poolall of the alleles that exist within a species are known as a gene pool, when mutations or genetic leakage occur new genes are introduced into the gene pool
- 11silent mutationsoccur when the change in the nucleotide has no effect on the final protein synthesized from the gene, this most commonly occurs when the changed nucleotide is transcribed to be the third nucleotide in a codon because there is degeneracy (wobble) in the genetic code
- 12missense mutationoccur when the change in nucleotide results in substituting one amino acid for another in the final protein
- 13nonsense mutationoccur when the change in nucleotide results in substituing a stop codon for an amino acid in the final protein
- 14chromosomal mutationsare larger scale mutations in which large segments of DNA are affected
deletion mutation - occur when a large segment of DNA is lost from a chromosome, small deletion mutations are considered frameshift mutations
duplication mutaiton - occur when a segment ofDNA is copied multiple times
inversion mutation
insertion mutation - occur when a segment of DNA is moved from one chromosome to another, small insertion mutaitons (includng those where the DNA is not from another chromosome) are considerd frameshift mutations
translocation mutations - occurs when a segment of DNA from one chromosome is swapped with a segment of DNA from another chromosome - 15inborn errors of metabolismthese are defects in genes required for metabolism, often times early intervention is required to prevent build up of toxic metabolites
- 16genetic leakageis a flow of genes between species, individuals from closely related species can mate to produce hybrid offspring
- 17genetic driftrefers to changes in composition of gene pool due to chance, tends to be more pronounced in small population
founder effect / bottleneck (drastically reduces the breeding population)/inbreeding
these all reduce genetic diversity - 18biometric techniquesthe statistical analysis of biological data
- 19monohybrid crosspunett square cross where only one trait is being studied
- 20test cross (aka back crosses)used to determine an unknown genotype
- 21dihybrid crossexpand the monohybrid, create a 4x4 punett square,
9:3:3:1 ratio for crosses between heterozygotes with complete dominance - 22sex linked (X linked) traitshemophilia is a sex linked trait,
an x chromosome carrying an affected allele is commonly given a subscript X_h
assume seX linked is X linked on the MCAT - 23chiasmapoint of cross over, that occurs between two genes, occurs more frequently if the genes are located far apart
- 24recombination frequencythe likelihood that two alleles are separated from each other during crossing over, roughly proportional to the distance between the genes on the chromosomes
tightly linked genes have recombination frequencies close to 0 percent, weakly linked genes have recombination frequencies approaching 50 percent as expected from independent assortment - 25genetic mapby analyzing recombination frequencies we can estimated the distance
one map unit or centimorgan corresponds to a 1 percent chance of recombination reoccuring - 26allele frequencyhow often an allele appears in a population if we took one sample from 50 of mendel's plants we could collect 100 copies of alleles for flower color, if 75 of these alleles were dominant allele we could say that the allele frequency of P is 75/100 = .75
- 27what is evolution and when does it NOT occur?evolution is the change in a populations gene frequencies
Hardy weinburg assumptions
-the population is very large (no genetic drift)
- there are no mutations that affect the gene pool
-random assorted mating, no sexual selection
- no migration
-the genes in the population are all equally sucessful at reproducing - 28hardy weinburg equationsp+q=1 (tells us the frequency of alleles in the population)
P^2 + 2pq + q^2 = 1 (provides information about the frequency of genotypes and phenotypes in the population)r - 29modern synthesis modelincorporates knowledge of genetic inheritance and changes in the gene pool to darwin's original theory,
differential reproduction when changes that can be favorable are more likely to be passed on - 30inclusive fitnessmeasure of an organism's success in the population, based on the number of offspring, success in supporting offspring and the ability of the offspring to support others
- 31punctuated equilibriumsuggests that changes in species occur in rapid bursts rather than evenly over time
- 32stabilizing selectionkeeps phenotypes within a specific range by selecting against extremes
- 33directional selectionadaptive pressure can lead to the emregence and dominance of an intially extreme phenotype
- 34disruptive selectiontwo extreme phenotypes are selected over the norm, darwin finches the beaks are either large or small, no intermediate phenotype
exacerbated by polymorphisms - naturally occuring differences in form between members of the same population
adaptive radiation - describes the rapid rise of a number of different species from a common ancestor, benefit of adaptive radiation is that it allows the various species to occupy different niches - 35isolationwhen two populations are geographically isolated for so long that the progeny can no longer freely interbreed
prezyogotic mechanisms - prevent formation of zygote completely, temporal isolation (breeding at different times), ecological isolation (living in different niches within the same territory), reproductive isolation (dick dont fit lol)
post zygotic mechanisms - allow for gamete fusion but yield either nonviable or sterile offspring - 36divergent evolutionrefers to independent development of dissimilar characteristics in lineages that share a common ancestor
cats and seals lol - 37parallel evolutionrefers to the process whereby related species evolve in similar way for a long period of time in response to analagous environmental section
tigers and jaguars - 38convergent evolutionrefers to the independent development of similar characteristics in two or more lineages not sharing a recent common ancestor
fish and dolphinsd
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- Flashcards on Genetics and Evolution, created by Xiao Yuan on 02/02/2018.
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