Inheritance Flashcards
genotype
the genetic constitution of an organism (the alleles it has for a gene)
phenotype
the expression of the genes and its interaction with the environment
allele
different forms of a particular gene found at the same locus on a chromosome. A single gene could have multiple alleles
homozygous
a pair of homologous chromosomes carrying the same alleles for a single gene
heterozygous
a pair of homologous chromosomes carrying two different alleles for a single gene.
recessive allele
an allele whose characteristic is only expressed in the phenotype if no dominant allele is present.
dominant allele
an allele whose characteristic will always be expressed in the phenotype
codominant alleles
two dominant alleles that both contribute to the phenotype- either by showing blend of both characteristics or the characteristics appearing together
monohybrid inheritance
where one phenotype characteristic is controlled by a single gene
dihybrid inheritance
where two phenotype characteristics are determined by two different genes present on two different chromosomes at the same time
sex-linkage
a gene whose locus is on the X chromosome
why are males more likely to express a recessive sex-linked allele
most sex-linked alleles are located on the X chromosome. therefore males only get one copy of the allele, so will express it even if it is recessive. Less likely for females as they get two alleles.
autosomal linkage
when two or more genes are located the same (non-sex) chromosome. only one homologous pair of chromosomes needed for all 4 alleles to be present.
epistasis
where two non-linked genes interact, with one gene masking or suppressing the other
two types of epistasis
recessive epistasis: where two homozygous recessive alleles mask expression of another allele
dominant epistasis: where one dominant allele masks expression of multiple other alleles
