BIO 2306 Lecture Notes - Lecture 17: Cytosine, Deoxyribonuclease I, Histone Deacetylase

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erinmoose740

10 Mar 2018

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Chapter 17: control of gene expression in eukaryotes. Regulation at multiple levels: changes in chromatin structure. When dna is tightly packaged, transcription is inhibited (can"t nd promoter) Dnase i hypersensitive sites: regions of the dna that is not highly packaged, thus are sensitive to digestion by dnase i: chromatin remodeling. Proteins bind to dna and reposition the nucleosomes. Allows transcription factors to bind to promoters: histone modi cation, methylation of histones. Can package the dna more or less depending on which animo acid of the histone are methylated. Demethylase remove methyl groups: acetylation of histones. Causes positive charge histone to be neutralized. Negatively charged dna no longer has an af nity for the histones. Deacetylase remove acetyl groups: dna methylation. Methyl groups added to cytosine in dna. Attracts deacetylases, which remove acetyl groups from histone. Cpg islands: stretched of dna high in guanine and cytosine nucleotides.

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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

BIO 2306 Lecture Notes - Lecture 17: Cytosine, Deoxyribonuclease I, Histone Deacetylase

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