Question

1. Are recessive alleles harmful?

2. Are all traits represented by only one gene?

3. In any given population, can there be more than two alleles present?

Answer 1

1) All recessive allels are not harmful. There are harmful recessive allels that can affect the organisms. But they only affect the organisms in a homozygous condition. In heterozygous condition they cannot affect the organisms since they are suppressed by the dominant gene. This allows the population to carry a recessive harmful allel from one generation to another.

2) No. All the traits are not represented by only one gene. The characters that are controlled by only one gene is called single gene traits. Attached earlobes (and free earlobes) is an example of single gene trait. There are polygenic traits in which a trait is controlled more than one gene. There are many examples for polygenic trait. Some of the common ones are , height in humans, blood group, eyecolour, skin colour etc.

3) In actual terms, a diploid individual posses only 2 allels for a particular trait or character. But in a population, there can be more than two allels for a character. For example, consider the allels that determine the blood group. In a population all the allels ie I^A, I^B, i can be present. But in a diploid individual only 2 of the allels will be present that determine his/her blood group.