Parontal generation Long brtstles Gray body Short bristles Ebony body stso'e sse0 Tostcross F, hotorozygote Homozygous rocessive Individual F2 gonoration s'so'e Sse'e Long bristles Gray body Nonrecombinant Short bristlos Ebony body Nonrecombinant Long bristles Ebony body Recombinant Short bristles Gray body Rocombinant Total: 537 542 76 75 Use of a testcross to distinguish between recombinant and nonrecombinant offspring - The parental generation begins with two different true-breeding strains to produce an F1 heterozygote. In the testcross, an F1 female that is heterozygous for both genes (s+se+e) is crossed to a male that is homozygous recessive for short bristles (ss) and ebony body (ee). The F2 recombinant offspring carry a chromosome that is the product of a crossover. (Note: Crossing over does not occur during sperm formation in Drosophila, which is unusual among eukaryotes. Therefore, the heterozygote in a testcross involving Drosophila must be the female.)

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Mitochondrial Mutations

A mitochondrion is a cellular organelle that serves as the site for cellular respiration and energy production (ATP or Adenosine Triphosphate). It is a double-membrane-bound organelle and is only present in eukaryotic cells.