natural selection and inheritance Flashcards
a genotype is…
genetic constitution of an organism
a phenotype is…
expression of the genotype and its interaction with the environment
alleles are…
variants of a different gene (eye colours), occur due to mutations in a gene that occur at different positions in the gene.
in diploids, chromosomes form pairs called…
homologous chromosomes
alleles at specific locus can be homozygous if they are…
the same type of allele or heterozygous if both alleles are different
an allele is dominant if…
it’s expressed in the phenotype of a heterozygote, so only 1 copy is needed for expression
an allele is recessive if…
it is not expressed in the phenotype of a heterozygote, so 2 copies have to be present for expression
codominant alleles are…
when both alleles are equally dominant and equally expressed in the phenotype
a monohybrid cross is when…
1.if you cross a homozygous dominant with a homozygous recessive, 100% of offspring would be heterozygous carriers
2. if you cross 2 heterozygous carriers then 25% of offspring would be homozygous dominant (unaffected), 50% would be heterozygous (unaffected) and 25% would be homozygous recessive (affected)
3:1 of unaffected to affected phenotypes
test crosses are…
used to determine an unknown genotype, the unknown genotypes crosses with homozygous recessive individual
if all offspring have dominant phenotype, then unknown genotype is homozygous dominant
if half of the offspring have the recessive phenotype, then unknown genotype is heterozygous.
homozygous is when…
you inherit one type of a particular gene
heterozygous is when…
you inherit two different types of a particular gene.
a dihybrid cross is when…
you inherit 2 different genes
autosomal linkage is…
2 or more genes located on the same autosome
less likely to be separated during crossing over so inherited together
offspring more likely to resemble parental genotype
sex linkage is…
gene is on the X chromosome
males more likely to have recessive conditions because they only require one copy of the sex-linked recessive allele for expression
inherited from mother
epistasis is…
interaction between 2 genes where one gene masks the expression of the other gene in the phenotype
the suppressing gene is called the epistatic gene+ the suppressed gene is called the hypostatic gene (can be dominant or recessive)
dominant= expression of dominant allele
recessive= 2 copies required to mask expression of hypostatic gene
9:3:4
chi-squared test
determines probability of unexpected result being due to chance or being significant
based off of null hypothesis= any difference that occurs between observed and expected results is due to chance
X^2= (sum of)[(O-E)^2]/E
a population is when…
group of organisms of the same species occupying a particular space at a particular time that can potentially interbreed.
species can exist as one or more populations
a gene pool is…
total no. of genes of every individual in an interbreeding population
allele frequency is…
how often an allele occurs in a populayion
Hardy-Weinberg principal
predicts allele frequencies will not change from generation to generation
Hardy-Weinberg assumptions are…
mating is random
no natural selection occurs
no mutation
no gene flow/genetic drift
population size in infinite
Hardy-Weinberg calculation…
p^2 + 2pq + q^2 = 1
p= frequency of one (usually dominant) allele
q= frequency of other allele
2pq= frequency of heterozygote
p^2= frequency of homozygous dominant
q^2= frequency of homozygous recessive
variation is…
phenotype variation within every population due to a combination of genetic and environmental factors
