To determine the number of chromosomes in the body cell of a person whose mother produced an egg cell containing two copies of chromosome 21, we need to consider the typical number of chromosomes in human cells.
Humans normally have 46 chromosomes in their body cells, arranged in 23 pairs. This includes one pair of sex chromosomes and 22 pairs of autosomes. If a mother produces an egg cell with two copies of chromosome 21, this means there is a duplication of this specific chromosome. However, this doesn’t alter the count of the total number of chromosomes unless it affects the overall structure of the chromosomes in the egg.
When this egg fertilizes, it combines with a sperm cell, which normally contains one copy of each chromosome (including chromosome 21). In this scenario, the body cell will still ultimately have a full set of pairs because the sperm contributes one copy per chromosome pair.
Thus, if the body cell of this person is genetically normal except for the duplication of chromosome 21 from the egg, they will still have a total of 46 chromosomes.
So the correct answer is c 46.