1. What does the term "gene expression" mean in terms of a eukaryotic cell? What percentage of the genes in a human cell are expressed at any given time? What is the most important point of regulation of gene expression? Gene expression means that different genes are expressed in a eukaryotic cell (all cells in an organism have the same genome). About 5-20% of genes in a human cell are expressed at any given time. The most important point is transcription. 2. What are the effects of histone acetylation and DNA methylation on gene expression? Once an mRNA reaches the cytoplasm of a eukaryotic cell, what are four mechanisms that can regulate the amount of active protein that can be produced from the sequence on the mRNA? Histone Acetylation attaches acetyl groups (--COCH 3 ) to positively charges lysines in histone tails. This neutralizes positive charges on the histone tails of a nucleosome, so they cannot bind to beighboring nucleosomes. This is turn makes the chromatin less dense. Methylation does the opposite, condensing the chromatin.
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