Question

Why do many syndromes have pleiotropic effects?

Why do males display X-linked recessive traits more frequently than females?

What are polygenic traits, and why are many traits polygenic?

Answer 1

Ans.1

Pleiotropic is having producing multiple effects from a single gene. in a pleiotropic gene may have an effect on several traits simultaneously, due to the gene coding for a product used by a myriad of cells or different targets that have the same signaling function.Quite, pleiotropy reflects the fact that most proteins have multiple roles in distinct cell types; thus, any genetic change that alters gene expression or function can potentially have wide-ranging effects in a variety of tissues.An example of pleiotropy is phenylketonuria, an inherited disorder that affects the level of phenylalanine in the human body. Phenylalanine is an amino acid that can be obtained from food. Other examples of pleiotropy are albinism, sickle cell anemia, and certain forms of autism and schizophrenia.

Ans.2.

Because male with a mutation in a gene on the X chromosome is typically affected with the condition. Because females have two copies of the X chromosome and males have only one X chromosome, so if male affected with this disease there are two chances first is affected and second is non affected but in female have a three condition first is affected second is Carrier and third is non affected. Thus in male one out of two conditions is affected while in females have a one out of three is affected. So X recessive diseases are more common among males than females.Examples of X-linked recessive disorders are hemophilia, color blindness, and Lesch-Nyhan syndrom.

Ans.3.

A "polygene” is a member of a group of non-epistatic genes that interact additively to influence a phenotypic trait. A polygenic trait is, whose phenotype is influenced by more than one gene. Traits that display a continuous distribution, such as height or skin color, are polygenic.

Many traits are polygenic because characteristic, of traits we call them phenotypes, that are affected by many different genes. Height in humans is very strongly genetically controlled, but there are many, different genes that control height. And this is why people are not the exact height of their parents.skin colour is an example of polygenic inheritance. This trait is determined by at least three genes and other genes are also thought to influence skin color. Skin color is determined by the amount of the dark color pigment melanin in the skin.