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MCAT

Unit 3: Lesson 1

Chemical and physical sciences practice passage questions

The influence of histones on genetic inheritance

Problem

Genetic inheritance is not only limited to the nucleic acid sequence passed from parent to offspring. Genetic regulation via histone structure is also an inherited element of gene expression. Post-translational modification of histone protein complexes allow for an additional level of regulation – by changing the structure of histone complexes, different loci of genetic code can be exposed or occluded, leading to the expression of different genes without changing a cell’s nucleic acid sequence.
Histone Methyltransferases are some of the enzymes responsible for modifying histone structure. The enzymes use SAM as their cofactor to add methyl groups to amino acids on the histone protein that contain amine groups on their side chains (arginine and lysine). By adding methyl groups to these amino acid side chains, the structure of the entire histone protein complex will change, thereby altering the expression of different genes.
What type of enzyme is being described in this passage?
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