Question

Read the passage and answer the following question.

Many mammalian cell membrane receptors associated with the immune system contain repetitive structures known as the immunoglobulin fold. Receptors containing even one of these folds are considered members of the immunoglobulin superfamily.

Which of the following explains this common feature in different molecules?

• A. All of the genes that produce these proteins used to be part of a much larger gene that fragmented in the past
• B. All of the genes in question are retrotransposons
• C. Most of the genes in question are introns that experienced mutations that removed the splice sequence
• D. The fold was so successful as a signaling molecule that it encouraged its propagation
• E. The fold is repetitive because of gene duplication

Answer 1

The correct option is E The fold is repetitive because of gene duplication

Repetitive gene products are produced by gene duplication. A duplicated gene produces the same protein in multiple repeats. Retrotransposons can amplify themselves but are not necessarily present in multiple copies at the same chromosomal location. Introns are noncoding sequences. Proteins are encoded by genes only; they are not a product of encouraged propagation caused by relative success in the functioning. So, the correct answer is option E.