Topoisomerase is the enzyme that can be added to correct the untwisting that is led to strain ahead of the replication fork.
Answer:
If T=tall and t=short, what will be the physical appearance of the offspring in the cross?
Explanation:
It looks like your question is incomplete, so I'll try to fill in the blanks.
The offspring will depend on the parents. Each parent will need two alleles, so each parent would have to be TT (tall), Tt (tall) or tt (short--this is the only way to have a short individual).
Here are all the possible crosses:
TT X TT = 100% TT (all tall)
TT X Tt = 50% TT, 50% Tt (all tall)
TT X tt = 100% Tt (all tall)
Tt X Tt = 25% TT (tall), 50% Tt (tall), 25% tt (short)
tt X tt = 100% tt (short)
Note that if there is a T present in the genotype (TT or Tt), that individual will be tall. The only way to produce short offspring is for the both parents to have a copy of the short allele (t).
