Question

The allele which is unable to express its effect in the presence of another is called:

• A. Supplementary
• B. Codominant
• C. Recessive
• D. Complementary

Answer 1

The correct option is C

Recessive

The correct option is C.

Explanation of the correct option:

1. Recessive alleles are expressed only if the individual has two copies of the allele i.e. they are in homozygous condition,
2. It is a genetic code that doesn't get expressed phenotypically if a dominant allele is present with it.
3. For example if t is recessive for short and T is dominant for tall then in genetic code Tt tall phenotypic character will be only expressed.

Explanation for the incorrect option:

Option A

1. Supplementary genes are two dominant genes that exist and interact together and produce a different phenotypic character from earlier than what gene produced alone.
2. These are non-allelic genes capable of producing independent traits.
3. For example color of maize grains is controlled by two factors R and P.

Option B

1. In co-dominance, the phenotype of offspring is a combination of both traits.
2. In this way of inheritance alleles of gene pairs in heterozygous conditions are fully characterized.
3. For example ABO blood grouping in which A, B, and O are alleles and A and B also co-dominate or exist together.

Option D

1. Complementary genes are found on different loci of genes but are expressed together for a single trait.
2. These also have their individual effect but also express single traits when existing together.
3. For example color of the flower in sweet pea plants, in these flowers can be white or purple but for purple to be expressed the dominant allele of both the genes should be present.

Final answer: The allele which is unable to express its effect in the presence of another is called a recessive allele.