The size distribution of exons coding for collagen helical domains in various vertebrates reveals a unique pattern. This pattern provides clues to the evolutionary history of the genes encoding fibrillar collagen α chains. What is this pattern?
A) The length of most exons is a multiple of 100 nucleotides.
B) Most exons code for 54, or a multiple of 54, Gly-X-Y repeats.
C) The length of most exons is a multiple of 30 nucleotides.
D) Most exons code for 6, or a multiple of 6, Gly-X-Y repeats.
E) None of the above.

Question

Quizplus · Accepted Answer

The size of the coding exons for collagen helical domains is often 54 or a multiple of 54 nucleotides. This suggests that duplications of an ancestral gene (that was 54 nucleotides long and coded for six Gly-X-Y repeats) gave rise to the helical domains in modern fibrillar collagens.

The Size Distribution of Exons Coding for Collagen Helical Domains