Question

If an egg cell of a diploid plant species has 10 chromosomes, the expected number of chromosomes in a double trisomic somatic cell of this species would be ............. (Answer in integer).

Hint:

In a trisomic condition, there is an extra chromosome for one chromosome pair. In a double trisomic condition, two extra chromosomes are present. The total chromosome count increases by 2 from the normal diploid number.

Answer 1

To solve this problem, we need to understand the concepts of diploid, haploid, trisomy, and double trisomy. Let’s break it down:

- In a diploid species, an organism has two sets of chromosomes: one set from the mother and one from the father. A diploid plant species with 10 chromosomes means it has 10 chromosomes in total in its diploid somatic cells. In this case, the number of chromosomes in its diploid somatic cells is 20 (2 sets of 10 chromosomes).

- The egg cell, which is haploid, contains only one set of chromosomes. Therefore, since the diploid number is 10, the haploid egg cell would have 10 chromosomes.

Now, let’s consider the concept of a "double trisomic" cell. A double trisomic cell is a somatic cell that contains two extra chromosomes, one from each of two different chromosomes. So, if we take a diploid somatic cell (which has 20 chromosomes) and add 2 extra chromosomes (one from each of two chromosomes), we end up with a total of:

\[ \text{Chromosome count in double trisomic cell} = 20 + 2 = 22 \]

Thus, the number of chromosomes in the double trisomic somatic cell will be 22 chromosomes. This is because the cell has one extra chromosome from each of two chromosomes.

Therefore, the correct answer is 22.