Chapter 9: Problem 28

While demethylation can convert thymine to uracil, deamination can convert cytosine to uracil. Suppose these two mutations occur in a cell. What would be the impact on the DNA structure?

Short Answer

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Answer: Demethylation and deamination can alter the DNA structure by replacing thymine or cytosine with uracil, disrupting the normal base pairing rules and leading to incorrect DNA replication or transcription. If these mutations go uncorrected, they could lead to harmful consequences such as genetic mutations, gene silencing, or the initiation of diseases like cancer.

Step by step solution

Understand DNA Structure

DNA (Deoxyribonucleic acid) is a double helix structure composed of two antiparallel strands. Each strand is made of nucleotides, which consist of a sugar molecule, a phosphate group, and a nitrogen base. The four bases in DNA are Adenine (A), Thymine (T), Cytosine (C), and Guanine (G). These bases form specific base pairs through hydrogen bonds: Adenine with Thymine and Cytosine with Guanine.

Demethylation

Demethylation is the process of removing a methyl group from a molecule. In the context of DNA, demethylation converts thymine (T) to uracil (U) by removing its methyl group (-CH3). The base pairing in the DNA would change due to this mutation. Uracil (U) would now pair with Adenine (A) instead of Thymine (T).

Deamination

Deamination is the removal of an amino group (-NH2) from a molecule, typically replaced by an oxygen atom. In the context of DNA, this process can convert cytosine (C) to uracil (U). As with demethylation, deamination changes the base pairing in the DNA strand. In this case, any cytosine that undergoes deamination will be replaced by uracil, which pairs with adenine (A) instead of guanine (G).

Impact on DNA Structure

Both demethylation and deamination can alter the DNA structure by replacing thymine or cytosine with uracil, which can disrupt the normal base pairing rules (A-T, C-G) and lead to incorrect DNA replication or transcription. The presence of uracil might cause errors in the DNA sequence, affecting the structure and function of proteins and other cellular components encoded by the altered sequences.

Consequence for the Cell

The cell has several DNA repair mechanisms in place to correct such errors and maintain genome integrity. However, if these mutations go uncorrected, they could lead to harmful consequences, such as genetic mutations, gene silencing, or even the initiation of diseases like cancer. Therefore, understanding the impact of demethylation and deamination on DNA structure is crucial for elucidating the relationship between DNA changes, gene function, and disease onset.

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While demethylation can convert thymine to uracil, deamination can convert cytosine to uracil. Suppose these two mutations occur in a cell. What would be the impact on the DNA structure?

Short Answer

Step by step solution

Understand DNA Structure

Demethylation

Deamination

Impact on DNA Structure

Consequence for the Cell

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