Inheritance Flashcards
what is phenotypic variation ?
variation in phenotype
how many genes is continuous variation usually influenced by ?
multiple (polygenic)
how many genes is discontinuous variation usually influenced by ?
one gene (monogenic)
F1 / F2 … means ?
generation of offspring
what sex chromosomes do males / females have ?
male - XY
female - XX
what is a sex-linked characteristic ?
allele located on a sex chromosome that codes for a characteristic
why are males more likely to show recessive phenotypes for sex-linked genes than females?
- most sex-linked genes carried by X
- males only have one X
- allele will be expressed as it is the only one
what is an autosome ?
any chromosome that isn’t sex chromosome
what does it mean if genes are linked ?
- located on same autosome
- alleles will stay together for independent assortment
- alleles will be passed onto offspring
what causes autosomal linked genes to be different to offspring ?
crossing over
what does ‘more closely linked’ genes mean and result in ?
- genes are closer together on the autosome
- less likely to be split up by crossing over
what is epistasis ?
allele of one gene masks (blocks) the expression of alleles of another gene
what is the recessive epistasis ratio ?
9:3:4
dominant both : dominant epistatic recessive other : recessive epistatic
what is the dominant epistasis ratio ?
12:3:1
dominant epistatic : recessive epistatic dominant other : recessive both
what are the parents for epistatic ratios ?
homozygous recessive and dominant
