In: Biology
If a daughter expresses a sex-linked recessive gene, she inherited the trait from:
a) her mother
b) her father
c) both parents
d) neither parents.
show work, thanks.
Answer : C. Both parents
Explanation : Sex-linked inheritance means that the gene causing the trait or the disorder is located on the either X or Y chromosome. As the daughter is expressing the gene, the trait is located in X chromosome because females do not possess Y chromosome. In case of recessive inheritance, both matching genes from both of the parents must be abnormal to cause disease. Someone who has only one abnormal gene and do not show any symptoms is called a carrier. In X-linked recessive inheritance, a mutation in a gene in the X chromosome causes the phenotype to be mostly expressed in males because they have only one X chromosome. In case of females the disorder occurs in individuals who are homozygous for the gene mutation, means an abnormal gene on the X chromosome from each parent would be required, since a female has two X chromosomes. Carrier females who have one copy of the mutated gene do not usually express the phenotype., Notwithstanding varying degree of expression in carrier females can be seen due to the differences in X-chromosome inactivation, which is basically known as skewed-X inactivation.
* X denotes normal chromosome whereas X' denotes affected chromosome.
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