Which of the following best describes how changes in the epigenome affect gene e

Question

Which of the following best describes how changes in the epigenome affect gene expression? a. Acetyl groups and methyl groups are attached to newly synthesized proteins leading to changes in structure and function of the target proteins. b. Mutations in the epigenome can lead to changes in the protein structure and therefore affect the protein function. c. The addition of methyl groups to cytosines interferes with base pairing and can lead to mutations. d. The presence or absence of acetyl groups on histones and methyl groups on cytosines determine if a gene can be expressed. Which of the following statements is true for specific transcription factors, but not true for general (basal) transcription factors? a. These transcription factors act in a tissue or time dependent manner to stimulate higher levels of transcription. b. These transcription factors form part of the transcription initiation complex. c. These transcription factors are proteins. d. These transcription factors bind to the TATA box in the core promoter. e. These transcription factors are necessary to recruit RNA polymerase to the promoter.

Explanation / Answer

22.) d. The presence or absence of acetyl groups on histones and methyl groups on cytosine determine if a gene can be expressed: There is an alteration in gene expression due to epigenesist. Epigenesis refers to heritable changes which does not involve any alteration in DNA sequence. There occurs a chemical modification in DNA and histone protein. Mainly methylation in DNA takes place and methylation, acetylation etc. in histone protein takes place.

Methylation occurs at 5’ end of cytosine and acetylation at N- terminal of histone occurs. Thus, these changes affect the gene expression.

23). a. These transcription factors act in a tissue or time dependent manner to stimulate higher level of transcription:

Transcription factors are proteins that can activate or repress transcription.

General transcription factors are required for transcription by all mRNAs. They are involved in initiation and carrying out transcription. TATA binding protein is an example of general transcription factors. General transcription factors also recruit RNA polymerase.

Specific transcription factors act specifically and promote transcription at maximal level.

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