A specific allele of the Bar gene causes narrowing of the eyes of the fruit fly. The gene is located on the X

| February 8, 2021 | education

A specific allele of the Bar gene causes narrowing of the eyes of the fruit fly. The gene is located on the X chromosome and is characterized by incomplete dominance: in females bb eyes are narrow – striped, in females Bb eyes are intermediate width, in females BB – normal. A female with normal eyes was crossed with a male with striped eyes. In the offspring of the first generation, all females had intermediate eye width, and males had normal eyes. They were crossed among themselves and received the offspring of the second generation. What proportion of all descendants of the second generation are females with striped eyes?

In females bb eyes are narrow – striped, in females Bb eyes are intermediate width, in females BB – normal.

A female with normal eyes was crossed with a male with striped eyes.

ХВХВ * ХbY

F1 (first generation) XBXb * XBY

F2 (second generation) XBXB XBXb XBY XbY

After crossing them: XBXB XBXB XBY XBY XBXb XBXB XBY XbY XBXb XbXb XBY XbY

Hence, the proportion of all offspring of the second generation of females with striped eyes (XbXb) is 8



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