inheritance Flashcards
define genotype
genetic constitution of an organism
define phenotype
expression of an organism’s genetic constitution, combine with its interaction with the environment
what is an allele
different forms of a particular gene found at the same locus (position) on a chromosome
a single gene could have many alleles
how many alleles per gene do diploid organisms carry
two
what is meant by a dominant allele
an allele whose characteristics will always appear in the phenotype, whether one or two are present
what is meant by a recessive allele
an allele whose characteristics only appears in the phenotype if no dominant allele is present, meaning two must be present
what is meant by codominant alleles
two dominant alleles that both contribute to the phenotype, either by showing a blend of both characteristics, or the characteristics appearing together
define monohybrid inheritance
where one phenotypic characteristic is controlled by a single gene
define dihybrid inheritance
where 2 phenotypic characteristics are determined by two different gene present on two different chromosomes at the same time
what is meant by sex-linkage
where an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual
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 this characteristic even if its recessive. since females get two alleles, this is less likely
which parent do males inherit sex-linked characteristics from
their mother
Y chromosme can only come from father therefore if mother is heterozygous for sex-linked alleles she is a carrier and may pass trait on
what is meant by autosomal linkage
where two or more genes are located on the same (non-sex) chromosome. in this case, only one homologous pair is needed for all four alleles to be present. for genes that aren’t linked, two homologous pairs are needed
what is meant by epistasis
where are two non-linked genes interact, with one gene either masking or suppressing the other gene
what are the two types of epistasis
recessive epistasis
dominant epistasis
