C785 Epigenetics Exam Latest -

C785 Epigenetics Exam (Latest - Actual Questions and Answers 100% Correct

• Proteins that promote coiling of DNA and help prevent DNA strands from

"tangling" are called?

Answer: Histones

The combination of DNA and histone proteins creates nucleosomes.

• Epigenetics. Given the following modification of the nucleosomes, dis- cuss

how the transcription and gene expression is impacted. In A the nucleosomes are less condensed, and in B they are more tightly wound. Would A or B foster the ability to have more active transcription of genes?

Answer: A

When the histones of the nucleosomes have DNA wound tightly around them, less DNA is available to be bound and activated by transcription factors.

• Some changes to the DNA do not modify the coding sequence of the DNA but do

affect its winding and unwinding from nucleosomes. These changes can increase or decrease the availability of DNA and hence, the transcription of a gene. These are called changes?

Answer: Epigenetic

Epigenetic changes result from modifications of the DNA that affect nucleosome spacing and, therefore, transcription. They do not alter the DNA sequence itself.

• Select all of the following that are involved in the process of actively tran scribing

a gene.

Answer:

Epigenetic modifications to nucleosomes

Transcription Factors Promoters RNA polymerase

• / 2

• What changes can occur to the DNA (ex. methyl groups) and to the histones that

will impact gene expression? Select all that apply

Answer:

methylation

Acetylation

• Which of the following statements about epigenetics is false?

Answer: The DNA sequence is permanently altered.

• Which of the following statements about epigenetics is True?

Answer: Environmental stimuli control gene expression.

Gene expression is influenced by chemical modifications of the DNA and/or histone proteins.Access to the promoter gene by transcription factors is affected.

• The LCT gene codes for Lactase, which is responsible for the breakdown of

lactose. Which of the following statements could explain how Lactase activity is increased in the presence of lactose?Answer: The presence of lactose causes nucleosomes to separate, exposing the LCT gene.

Tightly-packed nucleosomes impede transcription. The DNA becomes inaccessible to the transcription machinery and the gene is not exposed.

• Histone proteins can be chemically modified by addition of an methyl group. If

this causes nucleosomes to pack , the process of is decreased at those DNA sites.

Answer: more tightly; transcription

Changes to histone proteins or to DNA that result in tighter nucleosome packing make the DNA less available for transcription. Therefore, transcription is decreased.

• The LEP gene codes for an anorexigenic hormone. Interestingly, breast- feeding

has been shown to alter methylation of the promoter of this gene, leading to

• / 2