HEREDITY
LINKED GENES
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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A fly that received only y+w+m+ and ywm chromosomes from her parents was able to transmit different combinations of alleles to her offspring.
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A fly with a gray body and red eyes (wild type) was able to produce offspring with gray bodies and white eyes.
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True breeding yellow, white, miniature flies always had yellow, white, miniature offspring.
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None of these examples demonstrate crossing over.
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Detailed explanation-1: -Morgan’s Test Crosses In his initial test cross aimed at exploring the precise relationship between eye color and sex, Morgan bred white-eyed males (X wY) with wild-type red-eyed females (X +X +). This cross yielded only red-eyed offspring, as summarized in Table 3.
Detailed explanation-2: -Morgan discovered a mutation that affected fly eye color. He observed that the mutation was inherited differently by male and female flies. Based on the inheritance pattern, Morgan concluded that the eye color gene must be located on the X chromosome.
Detailed explanation-3: -The basic reason is that crossovers between two genes that are close together are not very common. Crossovers during meiosis happen at more or less random positions along the chromosome, so the frequency of crossovers between two genes depends on the distance between them.
Detailed explanation-4: -He concluded that closer the genes, greater the linkage and vice-versa.