Table of contents

1. Overview of Cell Biology2h 49m
2. Chemical Components of Cells1h 14m
3. Energy1h 33m
4. DNA, Chromosomes, and Genomes2h 31m
5. DNA to RNA to Protein2h 31m
6. Proteins1h 36m
7. Gene Expression1h 42m
8. Membrane Structure1h 4m
- The Lipid Bilayer
  38m
- Membrane Proteins
  25m
9. Transport Across Membranes1h 52m
10. Anerobic Respiration1h 5m
11. Aerobic Respiration1h 11m
12. Photosynthesis52m
13. Intracellular Protein Transport2h 18m
14. Cell Signaling1h 28m
15. Cytoskeleton and Cell Movement1h 39m
16. Cell Division3h 5m
17. Meiosis and Sexual Reproduction50m
18. Cell Junctions and Tissues48m
19. Stem Cells13m
- Stem Cells
  13m
20. Cancer44m
21. The Immune System1h 6m
22. Techniques in Cell Biology1h 41m

4. DNA, Chromosomes, and Genomes

The Epigenetic Code

Cell Biology

4. DNA, Chromosomes, and Genomes

The Epigenetic Code

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Multiple Choice

Which of the following histone tail modifications is most likely to cause closed chromatin?

Acetylation

Methylation

Phosphorylation

Ubiquitination

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Verified step by step guidance

Understand the role of histone tail modifications in chromatin structure. Histone modifications can either open (euchromatin) or close (heterochromatin) chromatin, affecting gene expression.

Recognize that acetylation of histone tails generally leads to an open chromatin structure. This is because acetylation neutralizes the positive charge on histones, reducing their affinity for the negatively charged DNA, thus loosening the chromatin.

Identify that methylation of histone tails can lead to either open or closed chromatin, depending on the specific amino acid residues that are methylated and the number of methyl groups added. However, certain methylation patterns, such as trimethylation of histone H3 at lysine 9 (H3K9me3), are associated with closed chromatin and gene silencing.

Consider phosphorylation, which can have varied effects on chromatin structure. It often plays a role in signaling pathways and can lead to either chromatin condensation or relaxation, depending on the context.

Ubiquitination typically marks proteins for degradation but can also influence chromatin structure. However, it is less directly associated with chromatin condensation compared to methylation.