Question

1.) In your own words, what is Dnmt1 and what does it do?

2.) In your own words, what is Dnmt3a and 3b, and what do they do?

3.) Identify two distinct ways that DNA methylation regulates gene expression. One way is related to histone modifications, the other way is not.

Under Regulating X Inactivation

4.) Describe how DNA-methylation and histone modifications play a role in X-chromosome inactivation.

Answer 1

ANSWER-

QUESTION 1) DNMT1 (DNA (cytosine-5)-methyltransferase 1) is an enzyme. This enzyme is responsible for maintenance DNA methylation which ensures the fidelity of replication of inherited epigenetic patterns.

QUESTION 2) The family of DNA methyltransferase enzymes, which consists primarily of DNMT1, DNMT3A, and DNMT3B.

The enzyme DNMT3A is responsible for de novo DNA methylation. Such function is to be distinguished from maintenance DNA methylation which ensures the fidelity of replication of inherited epigenetic patterns.

DNMT3B is a protein associated with immunodeficiency, centromere instability and facial anomalies syndrome.

QUESTION 3) DNA methylation regulates gene expression by recruiting proteins involved in gene repression or by inhibiting the binding of transcription factor(s) to DNA. During development, the pattern of DNA methylation in the genome changes as a result of a dynamic process involving both de novo DNA methylation and demethylation. As a consequence, differentiated cells develop a stable and unique DNA methylation pattern that regulates tissue-specific gene transcription.

(A) The CpG island promoter is unmethylated and allows binding of transcription factors, which is required for transcription initiation. (B) The CpG island promoter methylation prevents binding of transcription factors and results in gene silencing.

QUESTION 4) X-inactivation or X-chromosome inactivation is also called lyonization. It is a process by which one of the copies of the X chromosome present in female mammals is inactivated. The role of DNA methylation in X dosage compensation is to "lock in" the process initiated by such factors.

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