STOP Read This! The nuclei of human cells contain 22 pairs of autosomes and a pa
ID: 255438 • Letter: S
Question
STOP Read This! The nuclei of human cells contain 22 pairs of autosomes and a pair of sex chromosomes. In females the two sex chromosomes are XX and in males the sex chromosomes are XY. Unlike the autosomes, the X and Y chromosomes are non-homologous with the X likely containing around 800-900 genes that code for proteins compared to the Y chromosomes with only 50-60 genes. As a result, most sex-linked alleles are encoded on the X chromosome. Pedigree charts can be analyzed to determine if the allele causing a condition is located on an autosome or the sex chromosome. 22. Using the information in Read This above and model 3, is the hemophilia allele located on an autosome or sex chromosome? Explain your reasoning. STOPExplanation / Answer
Answer:- With the help of model 3 and the text written above the question it can be easily deduced that hemophilia is a X linked recessive disorder. This means that hemophilia allele is located on the sex chromosome, X chromosome to be specific.
In hemophilia, males are affected with this disease more rather than females. This happens because hemophilia is a X-linked recessive disorder and its allele is located on the X chromosome. Females have 2 X chromosomes (XX) and males have one X and one Y chromosome (XY). If the hemophilia mutant gene is present on one of the two X chromosome in the female there is still a healthy X chromosome that can compensate for the mutant and the female will not be affected by the disease (as the mutant is recessive in nature it will not express itself in front of a dominant normal gene). But the female will be the carrier of the diseases. If somehow both the X chromosomes of a female is mutated for hemophilia only then she will be affected with the disease, chances for which are very low. In males however, because of the presence of only 1 X chromosome if he gets the mutated chromosome from either of his parents he will not have another X chromosome to compensate for the mutant allele and will be affected with the disease. This is the reason why males are more affected with this disease as can be seen in the model 3. Based on all the information above it can be said that the mutant gene responsible for causing hemophilia is located on the sex chromosomes.
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