explain briefly the bridges experiment.what is carrier $ how would we know which was carrier $ which one is abnormal.
explain briefly the bridges experiment.what is carrier $ how would we know which was carrier $ which one is abnormal.
Homogametic sex can be a carrier for many things and in this case too the homogametic females are considered as carriers for a trait. Carrier carries the allele for a particular trait without exhibiting that trait.
Let us try to understand the experiment again
White eyed female with genotype XwXw was crossed with red eyed male with genotype XrY
Xr Y Xw XwXr XwY Xw XwXr XwY
Allele for red colour expresses itself even in the presence of white allele.
According to this cross all the females should have been red eyed while all the males should be white eyed.
But the results were different as a female was of white eye colour which is normally not possible, and hence is abnormal.
After studying the karyotype of the abnormal female it was found that there was non disjunction of X chromosome resulting in gametes with XwXw genotype in female.
In drosophila, the sex is determined by the ratio of X chromosomes to autosomes and so in this case the situation XXY per 3 pairs of autosomes results in female.
It was concluded that X chromosome carries the gene for eye colour as the abnormal female even with the presence of Y chromosome did not show red eye trait even though this Y chromosome was inherited from a progeny of red eyed males.
Homogametic sex can be a carrier for many things and in this case too the homogametic females are considered as carriers for a trait. Carrier carries the allele for a particular trait without exhibiting that trait.
Let us try to understand the experiment again
White eyed female with genotype XwXw was crossed with red eyed male with genotype XrY
| Xr | Y | |
| Xw | XwXr | XwY |
| Xw | XwXr | XwY |
Allele for red colour expresses itself even in the presence of white allele.
According to this cross all the females should have been red eyed while all the males should be white eyed.
But the results were different as a female was of white eye colour which is normally not possible, and hence is abnormal.
After studying the karyotype of the abnormal female it was found that there was non disjunction of X chromosome resulting in gametes with XwXw genotype in female.
In drosophila, the sex is determined by the ratio of X chromosomes to autosomes and so in this case the situation XXY per 3 pairs of autosomes results in female.
It was concluded that X chromosome carries the gene for eye colour as the abnormal female even with the presence of Y chromosome did not show red eye trait even though this Y chromosome was inherited from a progeny of red eyed males.
