population genetics and inheritance Flashcards
define genotype
genetic constitution of an organism, determined by combo of parents alleles
define phenotype
expression of genotype
define allele
different variations of the same gene
what is the difference between homozygous and heterozygous
homo - both alleles are the same
hetero - both alleles are different
what do monohybrid crosses show
how alleles of a single allele are inherited between generations
on a monohybrid cross what will 2 heterozygous individuals produce
a ratio 3:1 dominant: recessive
what is co-dominance
when both alleles expressed in phenotype simultaneously
give an example of co-dominance
human blood type has 3 different alleles IA, IB, IO
IA and IB are dom / IO is recessive
results in 4 blood groups (A, B, AB, O)
what is a dihybrid cross and what is the ratio for 2 heterosygous
how alleles of 2 genes are inherited
9:3:3:1
what are autosomes
chromosomes that aren’t sex chromosomes
what is autosomal linkage
when genes on the same chromosome are said to be linked
what is the expected heterozygous ratio for autosomal linkage
9:4:3 due to crossing over in meiosis
what is sex linkage
genes located on sex chromosomes linked
most sex-linked genes on X chromosome (Y chromosome smaller → has fewer genes)
why are males more likely to inherit sex linked traits
- females have two X chromosomes so 3 possible phenotypes → dominant, heterozygous, recessive → XAXA, XAXa or XaXa
- males have only one X chromosome → if mutant allele inherited, they will express the condition → no second X chromosome to mask the effect → XAY or XaY
what are the inheritance patterns of sex linked traits
- fathers do not pass X-linked traits to their sons
- mothers can pass on X-linked traits to both their sons and daughters → son affected, daughter affected or carrie
what is epistasis
when one gene affects the expression of another
what is variation
describes the differences in characteristics / phenotypes that exist
what can genetic variation be caused by
meiosis
mutation
random fusion of gametes
what is a gene pool
total of all alleles of all gene loci in population at one time
what does hardy weinberg state
the frequency of all alleles of a specific gene will remain constant between generations
what does hardy weinberg assume
- large population
- no migration
- random mating
- no mutation
- no natural selection
what is genetic drift
allele frequencies change due to chance
