Pleiotropy is the effect of a single gene on more than one characteristic. Select primary and secondary pleiotropy.

Date: 2015-10-07; view: 435.

Pleiotropy

Penetration of genes

Within a population some quantity of organisms have the allele. But the quantity of organisms that have the trait defined by this allele might be less. It means the penetration of allele is less than 100%.

Penetration (penetance) means characteristic of gene (allele) to realize itself in phenotype.

P = f/g x 100%,

P – penetration,

f – quantity of traits defined by the allele (gene) within the population,

g – quantity of the gene within the population

In the case of primary pleiotropy there isn't causal relationship between characteristics, and the characteristics arise simultaneously. An example is the cats that are white with blue eyes are often deaf, white cats with a blue and an yellow-orange eye are deaf on the side with the blue eye. Morphan's syndrome is a human heredity disease realizes by defects of aorta, lens of eye, fingers, and foots.

In the case of secondary pleiotropy there is causal relationship between characteristics, and the characteristics arise one after the other. An example is the "frizzle-trait" in chickens. The primary result of this gene is the production of defective feathers. Secondary results are both good and bad; good include increased adaptation to warm temperatures, bad include increased metabolic rate, decreased egg-laying, changes in heart, kidney and spleen. Sickle-cell anemia is a human disease originating in warm lowland tropical areas where malaria is common. Sickle-celled individuals suffer from a number of problems, all of which are pleiotropic effects of the sickle-cell allele. At the first the structure of a protein of erythrocytes changes, then the shape of erythrocytes becomes abnormal and red cells destroy more than normal erythrocytes.