Textbook Question
What is the chemical basis of molecular hybridization?
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7. DNA and Chromosome Structure
DNA Structure
0:31 minutesProblem 29
Textbook Question
In some organisms, cytosine is methylated at carbon 5 of the pyrimidine ring after it is incorporated into DNA. If a 5-methyl cytosine molecule is then hydrolyzed, what base will be generated?
Verified step by step guidance1
Understand the context: Cytosine can be chemically modified by the addition of a methyl group at the carbon 5 position of its pyrimidine ring. This modification is known as 5-methylcytosine and is a common epigenetic marker in DNA.
Recall the process of hydrolysis: Hydrolysis involves the breaking of chemical bonds in the presence of water. In the case of 5-methylcytosine, hydrolysis can lead to the removal of the amino group (-NH2) from the cytosine base, a process known as deamination.
Recognize the product of deamination: When cytosine undergoes deamination, it is converted into uracil. However, in the case of 5-methylcytosine, deamination results in the formation of thymine instead of uracil because of the presence of the methyl group at carbon 5.
Summarize the chemical transformation: The hydrolysis of 5-methylcytosine leads to the removal of the amino group, and the methyl group remains intact. This results in the generation of thymine, a base naturally found in DNA.
Conclude the reasoning: The base generated from the hydrolysis of 5-methylcytosine is thymine, which is chemically distinct from cytosine due to the presence of the methyl group and the absence of the amino group.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
DNA Methylation
DNA methylation is a biochemical process involving the addition of a methyl group to the DNA molecule, typically at the 5-carbon position of cytosine residues. This modification can influence gene expression and is crucial for processes such as genomic imprinting and X-chromosome inactivation. Methylated cytosines can affect the binding of transcription factors and the accessibility of the DNA for transcription.
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Hydrolysis of Nucleotides
Hydrolysis of nucleotides refers to the chemical reaction where water is used to break down nucleotides into their constituent parts. In the context of DNA, hydrolysis can lead to the release of nitrogenous bases, sugars, and phosphate groups. When 5-methyl cytosine undergoes hydrolysis, it is essential to understand which base is released as a result of this reaction.
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Cytosine and Its Derivatives
Cytosine is one of the four main bases found in DNA and RNA, and it can exist in various forms, including its methylated derivative, 5-methyl cytosine. Understanding the structure and properties of cytosine and its derivatives is crucial for predicting the outcomes of biochemical reactions, such as hydrolysis. When 5-methyl cytosine is hydrolyzed, it is important to recognize that it will yield cytosine as the base, despite the methylation.
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