Inheritance and Evolution

gentoype

gentoype

genetic constitution of an organism - refers to alleles present-BB/Bb-bb

phenotype

appearance of a characteristic due to the expression of the genotype and its interaction with the environment

alleles

different form of genes. can be dominant / recessive/ co dominant

dominant allele

always expressed in phenotype

recessive allele

only expressed when the genotype is homozygous recessive

codominant allele

both alleles are expressed in the phenotype

locus

position of a gene on a chromosome. alleles occupy the same locus on each member of a pair of homologous chromosome.

in a diploid organism, the alleles at specific locus may be heterozygous or homozygous

homozygous

both alleles are the same (dominant/recessive)

heterozygous

refers to both alleles differing

multiple alleles

there are more than two alleles of a particular gene. however, only two alleles can be present in a genotype - one on each member of a pair of homologous chromosomes

sex linked gene

where the gene is carried on only one type of sex chromosome- usually X

what is monohybrid inheritance

inheritance of one particular characteristic

why is a test cross used?

to determine the genotype of an organism with a dominant phenotype. involves crossing the organism with the homozygous recessive