Question

In sex-linkage, what is the specialty?
a) Atavism
b) Criss-cross inheritance
c) Reversion
d) Gene-flow

Answer 1

Inheritance of genes is the basis of the evolution of Earth. Sex-linkage is a characteristic of genes on the X-chromosome. Usually, the genes located on the X-chromosome are called sex-linked genes and the phenomena of transfer of X-linked traits are called the sex-linkage.

Complete answer:
● Atavism is the inheritance of traits from one generation to the next generation.
● Reversion is a reverse mutation in which the phenotypes of wild-type traits of an individual are restored in the cell, despite having altered phenotypic traits.
● Gene flow is also called gene migration. It is the transfer of genetic material from one generation to another, as a result of interbreeding between individuals of two different locations.
● Criss-cross inheritance is the type of inheritance pattern in which the characters of the mother are passed on to the son, while that of the father are passed on to the daughter.
● This inheritance type shows a crossing-over of sex-linked sister chromosomes, thus it is named the criss-cross inheritance by Thomas Morgan.
● The following diagram explains the criss-cross inheritance pattern of sex-linked genes:

● In the above figure, among the two parents, the father is unaffected and the mother is a carrier of X-linked disorder (Eg. Haemophilia).
● The parents gave birth to four progenies (F1 generation). The affected X chromosome is passed on to a son.
● A daughter is a carrier due to one affected X-chromosome from the mother and one unaffected X-chromosome from the father.
● The other two children, one boy, and one girl are normal.
● In the further generation (F2), the affected son would pass on the X-chromosome to his daughter and she would become the carrier of the disease.
● In case if the affected male marries a carrier or the affected female, his daughter will be affected.

Hence, the correct answer is option (B).

Note: The characteristics of sex-linked inheritance are;
The sex-linked traits are recessive in most of the cases. Males demonstrate more Sex-linked traits than females.
Males suffer more from sex-linked disorders due to the harmfulness of many sex-linked traits. Females are generally the carriers of sex-linked diseases. Do not get transmitted to the son if the mother does not exhibit them