Which statement about cytosine methylation is correct?

Which statement about cytosine methylation is correct?

• A. Cytosine methylation of CG sequences can be propagated in daughter DNA strands by maintenance DNA methyltransferases
• B. Epigenetics is the study of heritable changes that are due to changes in DNA sequences
• C. Cytosine methylation generally enhances transcription
• D. Histone modifications cannot be inherited by daughter cells

Answer: (A)

Cytosine methylation is an important epigenetic modification that typically occurs at cytosine bases within CG sequences in DNA. The statement regarding the propagation of cytosine methylation in daughter DNA strands accurately reflects how maintenance DNA methyltransferases operate during DNA replication. These enzymes recognize the existing methylation patterns on parental DNA strands and ensure that the newly synthesized daughter strands are appropriately methylated, thereby preserving the methylation state through cell divisions. This mechanism is crucial for maintaining gene expression patterns and cellular identity across generations of cells. The other statements do not accurately represent current understanding of epigenetics. The concept of epigenetics encompasses heritable changes that do not involve changes to the underlying DNA sequence itself, rather than changes that are due to DNA sequence alterations. Furthermore, cytosine methylation typically acts to suppress transcription rather than enhance it, directly impacting gene expression. Lastly, histone modifications can indeed be inherited by daughter cells, so this statement misrepresents the capabilities of histone modifications in the context of inheritance.

Cytosine methylation is an important epigenetic modification that typically occurs at cytosine bases within CG sequences in DNA. The statement regarding the propagation of cytosine methylation in daughter DNA strands accurately reflects how maintenance DNA methyltransferases operate during DNA replication. These enzymes recognize the existing methylation patterns on parental DNA strands and ensure that the newly synthesized daughter strands are appropriately methylated, thereby preserving the methylation state through cell divisions. This mechanism is crucial for maintaining gene expression patterns and cellular identity across generations of cells.

The other statements do not accurately represent current understanding of epigenetics. The concept of epigenetics encompasses heritable changes that do not involve changes to the underlying DNA sequence itself, rather than changes that are due to DNA sequence alterations. Furthermore, cytosine methylation typically acts to suppress transcription rather than enhance it, directly impacting gene expression. Lastly, histone modifications can indeed be inherited by daughter cells, so this statement misrepresents the capabilities of histone modifications in the context of inheritance.