<span>In Drosophila + indicates wild-type allele for any gene, m is mahogany and e is ebony.
Female parents are m+/m+ and males are +e/+e.
F1 are m+/+e, all wild type. F1 females are crossed with me/me males - the test cross.
Offspring will be : non recombinant m+/me, mahogany wild type or +e/me wild type ebony. OR
recombinant me/me mahogany ebony or ++/++ wild type.
As the two genes are 25 map units apart, the percentage of recombinants will be 25% and therefore percentage parental types will be 75%.
75% 1000 is 750. There are two parental types, so you would expect 375 of each. Therefore, you would expect 375 m+/me and 375 +e/me.
25% of 1000 is 250 split between two recombinants =125 of each. Therefore you would expect 135 me/me and 125 ++/++</span>
An individual having two different alleles of a specific gene is described as being Heterozygous for that specific trait.
You have a heterozygous genotype for that gene if the two versions differ. Being heterozygous for hair color, for example, means you have one allele for red hair and one allele for brown hair. The interaction of the two alleles influences which traits are expressed.
Being homozygous for a gene means you inherited two identical copies. It is the inverse of a heterozygous genotype, in which the alleles differ. People with recessive characteristics, such as blue eyes or red hair, are always homozygous for that gene. In genetics, heterozygous means having inherited different versions (alleles) of a genomic marker from each biological parent. As a result, a person who is heterozygous for a genomic marker has two distinct versions of that marker.
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