8B - Dihybrid crosses

Dihybrid cross

a genetic cross used to observe the inheritance of alleles and phenotypes of two genes.

Unlinked genes

genes located on different chromosomes, or far apart on the same chromosome. Unlinked genes have less chance of being inherited together.

Dihybrid cross of two hetrozygotes ratio

9:3:3:1

Linked genes

genes found close together on the same chromosome and likely to be inherited together.

Idependent assortment

the random orientation of homologous chromosomes along the metaphase plate during metaphase I

• - Because linked genes are on the same chromosome, they are inherited together and not separated during independent assortment.

Crossing over

The exchange of genetic material between non-sister chromatids during prophase I of meiosis, resulting in new combinations of alleles in daughter cells.

• This can occasionally result in linked genes being separated.

Map units

a measure of the distance between two genes on the same chromatid. Genes that are closer together are more likely to be linked to genes

Recombinant chromosome

a chromosome which is not identical to one of the homologous chromosomes in a diploid cell

Crosses with linked genes can result in strage ratios like 11.5:1:1:11.5