Question

Recessive genes a, b, c, d, e, and f are closely-aligned in a chromosome, but their order is unknown. Two deletions in the region are examined: one deletion uncovers genes a and e, and the other uncovers genes c and f. Which of the following could NOT be the order of genes?

a) a - b - c - d - e - f
b) b - a - d - c - e - f
c) d - c - b - a - e - f
d) f - e - d - c - b - a

Answer 1

The correct order of the genes is a - b - c - d - e - f, so option (b) b - a - d - c - e - f could NOT be the order of genes.

Step-by-step explanation:

The order of the genes can be determined based on the deletions observed. The deletion uncovering genes a and e tells us that a and e are adjacent to each other, and the deletion uncovering genes c and f tells us that c and f are adjacent to each other. Therefore, the correct order of the genes can be determined by placing a and e next to each other and c and f next to each other. Let's go through each option and see if it matches this order:

1. a - b - c - d - e - f - In this order, a and e are next to each other, and c and f are next to each other, so this could be the correct order.
2. b - a - d - c - e - f - In this order, a and e are not next to each other, so this cannot be the correct order.
3. d - c - b - a - e - f - In this order, a and e are next to each other, and c and f are not next to each other, so this cannot be the correct order.
4. f - e - d - c - b - a - In this order, a and e are not next to each other, and c and f are not next to each other, so this cannot be the correct order.

Based on this analysis, the correct order of the genes is a - b - c - d - e - f. Therefore, option (b) b - a - d - c - e - f could NOT be the order of genes.