Epigenetics

Questions and Answers

What is the primary result of hypermethylation in tumor suppressor genes?

Stimulation of cell growth

Increased gene mutation rates

Activation of transcription

Repression of transcription (correct)

Which type of DNA methylation is associated with global genomic implications in cancer development?

Oxidation

Acetylation

Hypomethylation (correct)

Hypermethylation

In organic chemistry, what defines a methyl group?

One carbon atom bonded to three hydrogen atoms (correct)

One carbon atom bonded to four hydrogen atoms

One carbon atom bonded to two hydrogen atoms

Two carbon atoms bonded to six hydrogen atoms

What is the effect of acetylation on proteins?

It impacts gene expression and metabolism significantly Signup and view all the answers

Which of the following statements about acetylation in bacteria is true?

90% of proteins involved in central metabolism are acetylated. Signup and view all the answers

What effect does plentiful food have on diabetes mortality in grandchildren?

It increases diabetes mortality. Signup and view all the answers

Which chemical change occurs at CpG sites during DNA methylation?

Conversion of cytosine to 5-methylcytosine. Signup and view all the answers

What is the primary role of DNA methylation in gene expression?

Regulating gene transcription and potentially silencing genes. Signup and view all the answers

Which regions of the human genome are typically not methylated?

CpG islands associated with promoters. Signup and view all the answers

What is the general fidelity of DNA methylation patterns in somatic cells during cell division?

High fidelity, transmitted to daughter cells. Signup and view all the answers

Study Notes

Transgenerational Epigenetic Inheritance

Increased diabetes mortality observed in grandchildren when food was plentiful, indicating epigenetic inheritance.
Paternal granddaughters of women who experienced famine in utero had shorter average lifespans.

DNA Methylation in Cancer

DNA methylation occurs primarily at CpG sites, converting cytosine to 5-methylcytosine via DNA methyltransferase.
Around 80-90% of human CpG sites are methylated; CpG islands (65% CG residues) are typically unmethylated and associated with 56% of mammalian gene promoters.
Aberrant DNA methylation leads to unscheduled gene silencing and is linked to cancer, manifesting as hypermethylation (gene repression) and hypomethylation (cancer progression).

Acetylation and Gene Expression

Acetyl is a functional group with the formula COCH3; methyl is an alkyl group from methane (CH3).
Acetylation significantly influences gene expression and metabolism, particularly in histones and metabolic enzymes.
Overexpression of histone deacetylases (HDACs) is associated with tumorigenesis and metastasis, impacting oncogene expression.

Histone and Chromosomal Structure

Human genome contains over 20,000 genes organized into 23 pairs of chromosomes, with DNA tightly wound around histones into nucleosomes.
Nucleosomes can move to expose DNA for transcription through histone modifications (tags) signaling whether a region should be open or closed.
Chemical modifications like phosphorylation, methylation, and acetylation affect histone charge and DNA winding.

Epigenetic Regulation

Changes in histone proteins and DNA impact gene expression without altering the DNA sequence, classifying them as epigenetic modifications.
The epigenetic regulation process allows for temporary changes that can persist through cell divisions, influencing transcriptional activity based on need.

Estrogen Receptor in Breast Cancer

Estrogen receptor alpha (ESR1α) serves as a critical prognostic marker in breast cancer; about two-thirds of cases are ESR1-positive.
Estrogen binding to ESR1 regulates mammary gland growth and differentiation, playing a role in breast cancer progression.