Question

Give examples of intra genic intersection.

Answer 1

In simple words, intra means within and so intragenic can be referred to as occurrence within a gene. Here, interactions take place between alleles of the same genes. Alleles are at the same locus and therefore it is termed as intralocus gene interaction. It includes four important Mendelian inheritance patterns.

Complete answer:
Intra genic intersection includes the following; Incomplete dominance, Codominance, Lethal genes and Pleiotropic genes. Each of them is explained well below.

Incomplete Dominance: It is also called semi-dominance. Here the dominant allele does not completely mask the expression or effects of the recessive allele. The resulting organism will show physical traits of both the alleles. One such example: In rose, the allele responsible for red color is dominant over the allele responsible for white color. The heterozygous roses will be of pink color (i.e. blend of red and white).

Codominance: Alleles of a gene pair in heterozygote are fully expressed. Here it does not matter whether the trait is dominant or recessive. Phenotype of offspring is a combination of parent phenotype. Example: AB blood group- A and B both proteins are present at same time. Every person has two gene copies from each parent.

Lethal genes: Allele that has ill effects on an organism and causes death of the organism. Examples of diseases by recessive lethal alleles are cystic fibrosis and sickle-cell anemia.

Pleiotropic genes: When one gene influences two or more unrelated phenotypic traits, the phenomenon is called Pleiotropy. One such example is phenylketonuria which is responsible for affecting the level of phenylalanine.

Note: There is also a phenomena of multiple alleles. It occurs when more than two alleles of a gene are present in a population. In such cases, phenotype depends on which two alleles exist in diploid individuals.