How many chromosome would be found in dog gametes?
how many chromosomes would be found in deer mouse brain cells?
how many chromosomes would be found in deer mouse gametes?

In dog gametes, there are half the chromosomes contained in normal diploid cells. In the normal diploid cell of the dog there are 78 chromosomes, thus, in dog gametes, there are 39 chromosomes.
Similarly, in deer mouse brain cells there are 48 chromosomes since brain cells are diploid cells.
In gametes there are half of that number, so in deer mouse gametes there are 24 chromosomes.