Mark has a friend named Chloe. How different are Mark's and Chloe's DNA?

The correct answer would be less than 1 percent.

As Mark and Chloe are individuals of the same species that is, Homo sapiens, that means they share more than 99 percent of the genome.

The genomes of both the individuals are arranged in 23 pairs of chromosomes.

The order of chromosomes, order of genes in each chromosomes are even same.

The difference between the nucleotide of two genomes in 1 in 100 and sometimes it is 1 in 1000.

This less than 1 percent change make individuals unique in themselves such as skin color, hair color, height et cetera.

0.01 % is the answer on apex