Question

Which of the following is a reliable way to recognize a sex-linked trait?

Group of answer choices

A All male offspring of an affected male are also affected

B Y-linked traits are inherited only from the maternal grandfather

C Observing a trait only in males

D Observing a trait only in grandfathers of the maternal line

Answer 1

Sex linked genes are the genes present in one of the sex chromosomes (allosomes) X and Y.

X-linked Genes : The genes which are present on the non-homologous portions of X chromosome and not on Y chromosome are called X-linked genes.

Y-linked Genes : The genes which are present in the non-homologous portions of Y chromosome and not present on X chromosome are called Y-linked genes. Y-linked genes are also called holandric genes.

Characteristics of sex-linked inheritance :

• Sex-linked traits are more frequently expressed in one sex than the other.
• X-linked recessive traits are more commonly expressed in males than in females as males have a single X chromosome and the counterpart for the gene present in x-chromosome will not be present in Y chromosome.
• X-linked traits show criss-cross pattern of inheritance. i.e a sex-linked trait will be transmitted from father to grandson through a carrier daughter and follow a zig-zag pattern of inheritance.
• Y-linked traits are inherited directly from father to son.

The correct answer choice that best describes a sex-linked trait is : All male offspring of an affected male are also affected.

Y-linked traits are only transmitted in paternal line. A mother doesn't have Y chromosome and is unable to transmit Y-linked traits.