Only concerned with phenotypes for classing test

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Unformatted text preview: r classing Test-cross genotype does not contribute to phenotype 10 wm/wm or wm wm O + ! O w+m+/Y or w+m+ What will the F1s be? 11 wm/w+m+ wm/Y testcross What will the F2 generation look like? Since the genes for eye colour and wing size are both on the X-chromosome, you might expect the F1 female to produce only wm (from P female) and w+m+ (from P male) gametes Therefore you would expect F2 males to be ONLY white-eye/mini wing or red-eye/full wing wm /Y w+m+ /Y 1:1 But…. 2 1 wm/Y wm/w+m+ wm /Y Recall: only concerned with phenotypes for classing w+m+ /Y wm+ /Y Not 1:1:1:1 w+m /Y 13 Unlinked genes assort independently Linked genes tend to assort together Recombination between non-sister chromatids during meiosis gives rise to recombinant phenotypes (trading of alleles) 14 wm/w+m+ w w+ w m m+ m+ X over in female between non-sister chromatids w+ m recombinant phenotypes 15 Recombination frequency depends on the gene pair note, it does not matter what his genotype is, since we are only looking at the males. Compare to genes w and y……………….. 16 white-eye/brown body Linkage red eye/ yellow body red-eye/brown body white-eye/brown body white-eye/brown body red eye/yellow body red-eye/brown body white-eye/yellow body 17 what does this tell us about the distance between genes m, y and w? Genes w and y are more closely linked than genes w and m We know this because the recombination frequency for the w and m genes (32.8%) is higher than that for the w and y genes (1%) A recombination frequency between 2 genes of 1% means only 1 out every 100 gametes has been reshuffled during meiosis in such a way that w and y genes on one chromosome have been disconnected from each other during recombination. Genes w and y behave as if they are connected to each other. During recombination in meiosis, they appear to travel together. 18 e.g., F1 gametes of w+y+m+/wym female PO + PO y+ w+ m...
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