Ch. 12: Genetics and Evolution Flashcards
what are genes
genetic sequences that code for heritable traits which can be passed from one generation to the next
how are genes organized
into chromosomes
what are alleles
alternative forms of genes
what are homologues
the two copies of each chromosome each cell possesses
what is a locus
the specific area on a chromosome where a gene/gene info is located
what is a homizygous genotype
situation i which only one allele is present for a given gene
ex: parts of the x chromosome in males
what occurs during complete dominance
phenotype of one dominant allele masks the phenotype of a recessive allele
what occurs during codominance
phenotype two dominant alleles are expressed simultaneously
ex: AB bloodtype
what occurs during incomplete dominance
phenotype is an intermediate of the two homozygous phenotypes
ex: red snapdragons = RR, pink snapdragons = Rr, white snapdragons = rr
what is penetrance
proportion of a population with a genotype who actually express the phenotype
probability of expressing phenotype if you have the genotype
what is expressivity
different phenotypic manifestations across a population with the same genotype
what does the law of independent assortment specify
inheritance of one gene does not affect another
mendelian law, complicated by discovery of linked genes
what is the gene pool
all of the alleles that exist within a species
how does mutation to a DNA sequence affect alleles
can potential result in mutant alleles
what is a mutagen
substance that can cause a mutation
how many nucleotides are affected in point shift mutations
one nucleotide
where do silent mutations usually occur
the wobble position (last nucleotide in a codon)
results in no effect on the final synthesized protein
how is the final synthesized protein affected with a missense mutation
appropriate amino acid is switched for another
how is the final synthesized protein affect with a nonsense mutation
appropriate amino acid chain is stopped short by AUG (methionine)
how is the final synthesized protein affect with a frameshift mutation
appropriate amino acid chain has inserted or deleted sequence due to shift in reading frame
how are chromosomal mutations different than point shift mutations
large areas of the chromosome are affected
what are deletion mutations
a large segment of DNA is lost from the chromosome
what are duplication mutations
a segment of DNA is copied multiple times in the chromosome
what are inversion mutations
a segment of DNA is reversed within the chromosome
what are insertion mutations
a segment of DNA is moved from one chromosome to another
what are translocation mutations
segment of DNA on one chromosome is swapped with that of another chromosome
how are genes affected by genetic leakage
genes flow from one species to another during inter-species mating
how is the gene pool affected by genetic drift
the composition of the gene pool changes due to chance, usually within isolated/small populations
what occurs during the founder effect
a small population of a species becomes physically isolated from the rest d/t changes in the natural environment, resulting in genetic drift of the gene pool
what occurs during bottlenecking
the amount of available breeders within a population are suddenly and drastically reduced
what gene pool changes result in inbreeding depression
limited genetic variation resulting in reduced fitness of the population
what gene pool changes result from outbreeding/outcrossing
introduction of unrelated individuals to a breeding pool, possibly increasing population fitness
how many traits are studied in a monohybrid cross
one trait
what individuals in a genetic cross are the P generation
the parents, the ones being crossed
what individuals in a genetic cross are the F generation
the offspring/filla, the ones being produced
when crossing two heterozygotes of a completely dominant trait, what are the genotypic and phenotypic ratios of the offspring?
Rr x Rr
genotype - 1:2:1 RR x Rr X rr
phenotype - 3:1 RR and Rr x rr
what is the phenotypic ratios of offspring for a heterozygous dihybrid cross
TtPp x TtPp
phenotype: 9:3:3:1
on what chromosome are sex-linked traits carried
seX-linked = X linked, recessive
can occur on Y but very, very rare
what is a chiasma
cross over of genes on homologous chromosomes, more likely with genes further apart on a chromosome
what does recombination frequency measure
likelihood that two alleles are separated from each other during crossover
what does a genetic map plot
the relative distance between genes on chromosomes
what are centimorgans
map units, the distance that corresponded to a 1% increased chance of recombination between two genes
25 map units apart = 25% chance of recombination
what is the hardy-weinberg equation
p + q = 1 where p is frequency of dominant allele and q is frequency of the recessive allele
therefore…
p^2 + 2pq + q^2 = 1
what do the criteria for the Hardy-Weinberg principle all imply
study population is NOT undergoing evolution; allele frequency will remain stable over time
what does the theory of natural selection imply about a species
certain characteristics/traits of individuals within a species may help those individuals have greater reproductive successes which increases the likelihood of those genes being passed on to offspring
how does stabilizing selection impact phenotypes
selection against extremes keeps phenotypes within a certain range
how does directional selection impact phenotypes
adaptive pressure shifts phenotype towards an extreme
how does disruptive selection impact phenotypes
selection of two extreme phenotypes over the norm
what is the effect of adaptive radiation
rapid rise of a number of different species, each with their own niche, from a common ancestor
what is the definition of species
the largest group of organisms capable of breeding to form fertile offspring
what is accomplished through speciation
a new species is formed
