Question 1 1 pts Which of the following is NOT a definition of epigenetics? A mi

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Question 1 1 pts Which of the following is NOT a definition of epigenetics? A mitotically or meiotically heritable state of different gene activity and expression (phenotype) that is independent of differences in DNA sequence (genotype). The sum of the alterations to the chromatin template that collectively establish and propagate different patterns of gene expression (transcription) and silencing from the same genome. Epigenetic changes influence the phenotype without altering the genotype. Alterations in gene expression that arise from environmental changes. Question 2 1 pts Which of the following is NOT true of nucleosome positioning: Most genes have a well positioned + 1 nucleosome In higher eukaryotes, there are typically nucleosome free regions at both the 5' and 3' ends of most genes. Positioning is fairly stereotypic across evolution. No transcription factor can bind to their cognate motifs if that motif is covered by a nucleosome

Explanation / Answer

Q1) option A

Epigenetics is defined as the study of changes in an organism due to differences in gene expression levels and not due to changes in the gene sequence.

All the options except A are alternate forms of the above definition.

Where as in option A, changes to genotype or genome sequence is mentioned. Such changes do not happen in epigenetics.

Q2) Option C is not true

Nucleosomes are a structure that compact DNA with the help of histones. They also help in gene regulation and have a key role in epigenetics. It is know that most genes have a well positioned +1 nucleosome and there are some nucleosome free zones that result in transcription. However, if the promoter sequnce is masked by a nucleosome, trasncription does not occur.

But position of nucleosomes are not conserved and hence are not stereotypic across evolution. IF this were the case, epigenetic difference would not have been observed.

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