Question

a certain compound that is an analogue of the base cytosine can become incorporated into dna. it normally hydrogen bonds just as cytosine does, but it quite often isomerizes to a form that hydrogen bonds, as thymine does. do you expect this compound to be mutagenic, and, if so, what types of changes might it induce at the dna level?

Answer 1

A cytosine analogue that hydrogen bonds like thymine is mutagenic as it can cause GC to AT base pair changes, leading to point mutations. Cells attempt to repair such mutations, but if unsuccessful, they can become permanent and lead to genetic diseases.

Step-by-step explanation:

Yes, a compound that is an analogue of the base cytosine and isomerizes to a form that hydrogen bonds like thymine is expected to be mutagenic. This analogue can be incorporated into DNA during replication. When it adopts the bonding characteristics of thymine, it can lead to incorrect base pairing during DNA replication. Specifically, if this compound pairs like thymine instead of cytosine, it could potentially turn a GC base pair into an AT base pair, thereby introducing a point mutation.

Chemical mutagens such as this base analogue can cause various types of mutations, such as transitions (where a purine is replaced by another purine or a pyrimidine is replaced by another pyrimidine) or transversions (purine for pyrimidine substitutions and vice versa), which can lead to mispairing and thus genetic mutations after several rounds of replication.

Cells have mechanisms like DNA polymerase proofreading activity and mismatch repair to correct such errors. However, if these mechanisms fail, the mutations can become permanent, leading to possible genetic diseases or contributing to the evolution of a species.