Answered: Which of the following are examples of…

Human Anatomy & Physiology (11th Edition)

11th Edition

ISBN:9780134580999

Author:Elaine N. Marieb, Katja N. Hoehn

Publisher:Elaine N. Marieb, Katja N. Hoehn

Chapter1: The Human Body: An Orientation

Section: Chapter Questions

Problem 1RQ: The correct sequence of levels forming the structural hierarchy is A. (a) organ, organ system,...

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Question

Which of the following are examples of molecular changes that
can have an epigenetic effect on gene expression?
a. Chromatin remodeling
b. Covalent histone modification
c. Localization of histone variants
d. DNA methylation
e. Feedback loops
f. All of the above

Expert Solution

Step 1

Epigenetic effects are such changes that bring about changes in the phenotypic expression of a gene without causing any changes in the DNA (deoxyribonucleic acid) sequence.
Epigenetic effects are helpful in determining whether the genes are in switched OFF or in switched ON mode.
Additionally, epigenetic effects can influence protein synthesis in many cells and make sure that only essential proteins are synthesized.

Step 2

Option A: Chromatin remodeling

Chromatin remodeling can be described as the rearrangement of chromatin thread from its condensed shape to a state that is accessible to the transcription machinery.
This helps the transcription factors and DNA binding proteins in accessing the DNA and hence controlling gene expression.
Chromatin remodeling just changes the arrangement of chromatin without causing any structural changes in the DNA sequence.

Option B: Covalent histone modification

Covalent histone modification is a post-translational modification in histone proteins with the help of methylation, phosphorylation, and so on.
The post-translational modifications that occurred in histone can pose an impact on the gene expression by the help of alteration in chromatin structure.
The covalent histone modification does not cause any structural changes in DNA

Option C: Localization of histone variants

Histone variants are special proteins that work as a substitute for the core histone proteins in the nucleosome of eukaryotic organisms.
The variants of histone protein help provide a diversity of functions in a cell including regulation of gene expression without causing any structural changes in the DNA.

Option D: DNA methylation

Methylation of the DNA is a process in which a methyl group is introduced on the molecule of DNA.
Methylation of DNA helps in the repression of gene expression.
DNA methylation has the tendency to alter the activity of DNA without causing any changes in the gene expression.

Option E: Feedback loops

Feedback loops in a cell provide the ability to regulate their inner state for adapting them to environmental and genetic stress.
The epigenetic regulations generated a positive feedback loop that along with gene regulation can result in expression memory.

Option F: All of the above

The chromosomal remodeling only rearranges the chromatin threat and is responsible for epigenetic effects.
Covalent histone modification is a post-translational modification that is responsible for epigenetic changes.
Localization of histone variants helps in controlling gene expression and hence brings epigenetic changes.
DNA methylation suppresses the gene activity without causing any structural changes and it is epigenetic modification.
Feedback loops with gene regulation bring expression memory and regulate epigenetically.

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