Answer: 35 chromosomes
Step-by-step explanation:
In sexually reproducing species like dogs, the number of chromosomes in the gametes (sperm and egg cells) is only half that of the somatic cells (cells in the body other than gametes). This results from the meiotic process, which cuts the number of chromosomes in half.
We can presume that the somatic cells' chromosome count is diploid (2n) as the tissue sample from the dog's liver has 70 chromosomes. Consequently, the dog's gametes would contain 35 haploid (n) chromosomes (half of 70).
Thus, the dog's gametes should include 35 chromosomes.