BIOA01H3 Lecture Notes - Lecture 29: Histone Code, Methylation, Lysine

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5 Jan 2018

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Lec 29: regulation of gene expression in eukaryotes. Can occur at many levels: epigenetic control, transcriptional control, translational control. Dna in chromatin is inaccessible to the transcription until it is remodeled. Chemical modification of histone tails repositions nucleosomes and exposes stretches of. Occurs during development and in response to environmental cues. Sequence of dna remains the same, tails can be modified. Compacted with tails that are lysine rich and lysine amino acids can be altered. Further compaction of dna makes it inaccessible by adding methyl groups. If tails are modified with acetyl group, this loosens the region and makes the dna accessible. Patterns of modifications = histone code = affects chromatin structure and gene. Methyl groups added to histone tails result in further compaction. Acetyl groups added to histone tails result in less compaction. Methylation is the addition of methyl groups. Acetylation is the addition of acetyl groups.

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QUESTION 3

What is the purpose of chromatin-remodeling enzymes in human cells?

The enzymes control the rate of translation of an mRNA transcript

The enzymes add phosphate or methyl groups to histone tails

The enzymes slide nucleosomes farther apart or closer to each other

The enzymes send damaged proteins to the proteasome for degradation

The enzymes cause DNA looping to occur

QUESTION 10

If you can drink milk as an adult, it means that you have inherited a mutation in the an enhancer for your lactase gene (the gene that encodes the enzyme you need to break down lactose). Predict the effect of this mutation:

The mutation changes the number of domains in the enzyme, which makes it work more efficiently

The mutation changes the amino acid sequence of the lactase protein

The mutation increases the number of copies of the lactase gene that will be found in your genome

The mutation changes whether the lactase sequence is found in an intron or exon

The mutation affects the expression of the lactase gene

QUESTION 12

What determines where in the genome a transcription regulator will bind?

Transcription regulators bind to the 5' UTR region of a gene

Regulators bind via complementary base-pairing to certain DNA molecules

Covalent bonds form between the transcription regulator and the atoms of the DNA backbone

Every eukaryotic gene has a different transcription regulator that will bind to the 5' end of the gene

Transcription regulators bind to specific DNA sequences via multiple weak non-covalent interactions

QUESTION 15

What is the histone code used for?

		Phosphorylation and acetylation of DNA affect its ability to be compacted
		Changes to the sequence of DNA change whether DNA will wrap around histone proteins
		Covalent modifications of histones affect the ability of the transcription initiation complex to form
		Histones provide the codon sequences needed for translation to occur
		The histone code affects which amino acids will get added to a polypeptide

Synergism in transcriptional regulation occurs when two transcription factors have a much greater effect when they are both active than would be predicted if one added their individual effects.
A. True
B. False

The N-terminal region of histones extends from nucleosomes. These histone tails can be covalently modified to signal that a gene in the region should be transcribed. What is the covalent modification?
A. Adding a poly A tail
B. Adding acetyl groups
C. Removing acetyl groups
D. Removing a poly A tail

You are studying how the estrogen receptor regulates expression of a particular gene in breast cancer cells grown in a test tube. You examine cells grown in the presence of estrogenic hormones. Using various biochemical techniques, you find that the activated estrogen receptor [i.e., with hormone(s) bound] binds to cis regulatory sequences in the gene of interest and recruits (physically interacts with) a protein that has histone deacetylase activity. Based on this information, do you predict that estrogen hormones induce transcription, have no effect on transcription, or suppress transcription of the target gene?
A. No effect
B. Induce
C. Suppress

BIOA01H3 Lecture Notes - Lecture 29: Histone Code, Methylation, Lysine

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