Final answer:
The number of CAG repeats increases due to genomic instability and mutations, particularly trinucleotide repeat expansion, where replication slippage leads to extra repeats that are passed down to future generations.
Step-by-step explanation:
The increase in the number of CAG repeats in each generation can be due to a phenomenon known as genomic instability, especially during meiosis.
Specifically, this is associated with a type of mutation called trinucleotide repeat expansion.
During DNA replication, slippage can occur, leading to the addition of extra CAG repeats.
These expanded repeats can then be passed to the subsequent generations, often resulting in a greater number of repeats with each generation.
Besides, the enzyme telomerase may play a role in maintaining these repetitive sequences at the chromosomal ends, though its impact on trinucleotide repeat expansion is less direct.
Moreover, environmental and physiological factors can also influence the mutation rate, contributing to genetic variation.