BIOL 123 Lecture Notes - Lecture 5: Methylation, Genome Size, Heritability

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1 Jan 2021

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Gene control region: (upstream section) refers to an upstream section of dna that includes the promoter region as well as other regulatory sequences that influence the transcription of dna. Repressor: proteins that bind to a sequence of dna or rna and inhibit the expression of one or more genes it attaches to upstream region and blocks the advance of the transcribing molecule = gene not expressed. Exons/introns = give flexibility: alternative splicing: describes the process of combining different subsets of exons together, yielding different mrna transcripts from a single gene. Proteins can be modified after translated post-translational regulation may involve addiction of elements or the protein may be cleaved into subunits, or undergo chemical reactions. Regulation of gene expression and protein modification can change in a matter of seconds. Two mechanisms for long-term changes: methylation: involves addition of methyl groups to dna (can silence genes, coiling: prevents gene expression because transcription machinery can"t reach.

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Discussions Questions (4,2) Please help me Answer ALL to compare to my answers and Thank you with details & clarity!

3. Most regulatory proteins (activators or repressors) form dimers before they can bind. What are the advantages of dimerization of these proteins? Why do heterodimers bind different DNA sequences than homodimers? How might dimerization be used to regulate gene expression?

4. Architectural like HMGâs can bind to DNA and cause the DNA to bend at a sharp angle. Some of these protein promote transcription even though they do not contact the RNA Polymerase, GTF or any other regulatory protein. What is a plausible explanation for how these DNA bending proteins influence gene expression?

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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

1 DNA sequences found in introns provide [A] amino acid sequence information.

[B] regulatory information.
[C] no known useful information.

[D] structure for the gene.
[E] alternative DNA splicing possibilities.

3. The TATA box is a(n)
[A] sequence close to the promoter region of many genes.
[B] square-shaped sequence.
[C] enhancer consensus sequence.
[D] activator sequence necessary for proper translation.
[E] None of the above

5. Regarding genes and gene expression, which of the following is not a difference between prokaryotes and eukaryotes
[A] Eukaryotic DNA does not contain a TATA box close to the initiation site as does prokaryotic DNA.

[B] In eukaryotes, RNA polymerase requires

'transcription factors'or initiation.

[C] Prokaryotic genes are often grouped together in

operons.

[D] In eukaryotes, the regulation of several genes at once requires common control elements in each of the genes.
[E] There is a diversity of eukaryotic polymerases that is reflected in the diversity of eukaryotic promoters.

10) In eukaryotic cells, a repressor

[A] is made of DNA.
[B] binds to the enhancer region to block transcription. [

C] is located both upstream and downstream from the promoter.
[D] binds to the operator to block RNA polymerase.

[E] binds to a silencer to reduce transcription rates.

Coordinated regulation of genes in eukaryotic cells [A] is the result of positioning the same regulatory sequence in front of each gene.
[B] results from all of those genes being under the control of one promoter.

[C] occurs because related genes all have the same

operons.
[D] occurs because enhancers cause DNA to bend.

BIOL 123 Lecture Notes - Lecture 5: Methylation, Genome Size, Heritability

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