Final answer:
A mutation where cytosine is replaced with adenine changes the DNA structure by altering base pairs, converting a CG pair into an AT pair. This type of mutation, a transversion, can affect the genetic code and lead to various consequences if uncorrected. It is one way chemical mutagens can induce alterations in the organism's DNA.
Step-by-step explanation:
Impact of Cytosine Replacement by Adenine on DNA Structure
When a mutation occurs and cytosine is replaced with adenine, this will disrupt the normal base pairing in DNA. Cytosine normally pairs with guanine (C-G), but if it is replaced with adenine, the mutated DNA strand will attempt to pair the adenine with thymine (A-T), which is its correct pairing partner. This results in the conversion of the original CG base pair to an AT base pair. This type of mutation is known as a transversion, which is a substitution mutation where a purine is replaced with a pyrimidine, or vice versa. The consequence of this mutation impacts the genetic code, as it can lead to the synthesis of erroneous proteins or have regulatory effects on gene expression. If uncorrected, this change could potentially contribute to diseases or various traits depending on the location and function of the affected gene.
In a typical DNA repair situation, either the incorrect base would be excised and replaced with the correct base, or if the mutation is not repaired, it may be kept and passed on during successive rounds of DNA replication, possibly leading to permanent changes in the organism's genome. Thus, in the context of chemical mutagens like hydroxylamine, inducement of such mutations could lead to significant alterations in an organism's DNA sequence over time.