That would be the Endoplasmic Reticulum my good friend hope this helped... :D
The HTT mutation that causes the Huntington's Disease involves a DNA segment otherwise known as a CAG trinucleotide repeat.
Cross: Ib Ib × Ia Ib
Offspring: IaIb , IbIb, IaIb, IbIb
ab = 50%
b = 50%
a = 0%
In short, Your Answer would be Option A) 0%
Hope this helps!
Topoisomerase is the enzyme that can be added to correct the untwisting that is led to strain ahead of the replication fork.
I would say D narrow temperature. Most other planets are too hot or cold to sustain life.