Home Genetics PLEIOTROPY

PLEIOTROPY

by Ramneet Kaur
1507 views

Pleiotropy

Pleiotropy is a condition in which single gene affects many characters or single gene affects many phenotypes.

  • It occurs due to inter-relationship between metabolic pathways that contribute to the formation of the different phenotype.
  • Effect of the gene is more evident in one trait and less evident in other traits.

EXAMPLE 1:

Gene for Phenylketonuria: 

  • Causes mental retardation and reduces skin and hair pigment.
  • It is an autosomal recessive metabolic disorder. Gene present on chromosome 12.
  • The gene in homozygous condition lacks Phenylalanine hydrolase enzyme, which converts Phenylalanine to Tyrosine.
  • Phenylalanine starts accumulating in blood, where it changes into Phenylpyruvic acid which is toxic to the Central Nervous System, damages the brain and causes mental retardation.
  • Melanin, the pigment is formed from Tyrosine. As Tyrosine is not formed there is a reduction in skin & hair pigment.

EXAMPLE 2:

Gene for Sickle cell anaemia:

  • Occurs due to an autosomal recessive gene.
  • Gene in homozygous condition alters the Haemoglobin, it forms Sickle cell haemoglobin HbS.
  • It makes RBC sickle shaped, rigid and short lived. Due to which the person becomes anaemic, oxygen carrying capacity decreases and clogging of arteries occurs.
  • Gene in heterozygous condition is codominant.

EXAMPLE 3:

Gene for starch synthesis in Pea.

BB, dominant gene in homozygous condition:

  • More effective in starch synthesis.
  • Starch grains are of larger size.
  • Seeds are round.

bb, recessive gene in homozygous condition:

Advertisements
  • Less effective in starch synthesis.
  • Starch grains are of smaller size.
  • Seeds are wrinkled.

Bb, gene in heterozygous condition:

  • More effective in starch synthesis.
  • Seeds are round.
  • Starch grains are of intermediate size as the gene shows incomplete dominance.

EXAMPLE 4:

Gene for Marfan Syndrome:

  • Occurs due to an autosomal dominant gene.
  • It is a genetic disorder of connective tissue.
  • It is characterized by long limbs, hypermobility of joints, lens dislocation, and are susceptible to cardiac diseases.

EXAMPLE 5:

Gene for white eye color in Drosophila:

  • It occurs due to a recessive gene present on the X chromosome.
  • It also causes depigmentation in many parts of the body.

ALSO WATCH: Pleiotropy

You may also like

Leave a Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Lets make Biology simple

This website uses cookies to improve your experience. We'll assume you're ok with this, but you can opt-out if you wish. Accept Read More

Subscribe
SUBSCRIBE NOW

Join Our Newsletter Today!

Stay updated with all latest MCQs, Topic Summary, Mnemonics, Videos, tips & tricks for Biology.
close-link

Send this to a friend

Skip to toolbar