A trait is caused by a rare dominant autosomal allele with full penetrance. Practically all individuals with the trait are heterozygous and result from matings between affected and normal individuals. What would be the expected concordance values for monozygotic and dizygotic twins?

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Social Studies

Lane Poole

27 January, 12:14

A trait is caused by a rare dominant autosomal allele with full penetrance. Practically all individuals with the trait are heterozygous and result from matings between affected and normal individuals. What would be the expected concordance values for monozygotic and dizygotic twins?

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Rodolfo Bryan · Answer 1

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Explanation:

Concordance: This is a term used in genetics. This term is used to imply the presence of the same trait/characteristic in both the members of a pair of twins.

Twins can be of 2 types. They are monozygotic twins and Dizygotic twins. Monozygotic twins are identical twins, i. e. they are formed from one zygote that later splits into two forming two embryos.

Dizygotic twins are non-identical twins or fraternal twins formed from the fertilization of two different eggs with two different sperm cells.

Concordance values can be calculated as:

C = Number of concordance pairs / (number of concordant pairs + number of discordant pairs)

Monozygotic twins generally have a concordance value of 44% for a specific trait.

Dizygotic twins have a concordance value of less than 5 % for a trait.

For identical twins the number of concordant pairs would be 50 out of 100. concordant pair would be

For non-identical twins, the number of concordant pair would be 17 out of 100.

For a recessive trait to be expressed, both the parents should be heterozygous for that trait.