BIOLOGIA MOLEKULARNA - Seminarium
LISTA 7
Chromosomy i kontrola ekspresji genów u Eukaryota
1. Match the DNA polymerase in the left column with the function or property with witch it is associated from the right column.
(a) DNA polymerase α
(1) Involved in chromosomal DNA repair
(b) DNA polymerase β
(2) Involved in chromosomal DNA replication
(c) DNA polymerase γ
(3) Involved in mitochondrial DNA replication
(d) DNA polymerase δ
(4) Synthesizes leading strand in nucleus
(e) DNA polymerase ε
(5) Synthesizes lagging strand in nucleus
2. Which of the following statements about histones are correct?
(a) They are highly basic because they contain many positively charged amino acid side chains.
(b) They are extensively modified after their translation.
(c) In combination with DNA, they are the primary constituents of chromatin.
(d) They account for approximately one-fifth of the mass of a chromosome.
3. Which of the following statements about nucleosomes are correct?
(a) They constitute the repeating units of a chromatin fiber.
(b) Each contains a core of eight histones.
(c) They contain DNA that is surrounded by a coating of histones.
(d) They occur in chromatin in association with approximately 200 base pairs of DNA, on average.
4. Which of the following statements about eukaryotic genes that are actively being transcribed are correct?
(a) They are cell-type specific.
(b) They are highly condensed.
(c) They are more susceptible to hydrolysis by DNAase I than are silent genes.
(d) They are developmentally regulated.
(e) They can be detected by chromatin immunoprecipitation.
5. Specific combinatorial control of transcription
(a) is enabled by specific interactions between transcription factors and specific DNA sequences.
(b) allows a given regulatory protein to have different effects depending upon the neighboring proteins with which it is associated.
(c) is effected by transcription factors, some of which do not themselves interact with DNA.
(d) depends upon the assembly of multicomponent nucleoprotein complexes.
(e) results from the ability of one protein to recruit another to a complex.
6. Which of the following statements about steroid hormones are correct?
(a) They bind to a seven-helix transmembrane receptor to initiate a series of phosphorylations that culminate in gene transcription.
(b) Upon binding to their specific receptor proteins, they may enable the receptors to bind specific DNA sequences.
(c) They activate specific protein kinases and protein phosphatases.
(d) They are recognized by members of the nuclear receptor superfamily of proteins.
(e) They require plasma membrane transporters to go from the blood to the cytosol.
BIOLOGIA MOLEKULARNA – Lista 7 – Chromosomy i kontrola ekspresji genów u Eukaryota.
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(a) are dimers.
(b) bind to response elements, which are specific DNA sequences at or near the genes the hormones control.
(c) undergo conformational changes when they bind their ligand.
(d) contain zinc finger domains.
(e) interact with coactivators and corepressors in a manner dependent on their ligands.
8. The tails of histones
(a) when acetylated have lower affinity for DNA.
(b) are involved in recruiting chromatin-remodeling engines that move nucleosomes.
(c) when acetylated, serve as substrates for histone deacetylases.
(d) have their positive charges reduced by acetylation.
(e) when acetylated interact with the bromodomain of many eukaryotic transcription factors when that domain is brominated.
9. Unlike bacterial RNA polymerases, eukaryotic polymerases have relatively low affinity for their promoters and therefore often depend on several activator proteins for initiation of transcription. Thus, while many bacterial genes are subject to negative regulation by repressor proteins, eukaryotic genes are more likely to be under positive regulatory control. What are the advantages of positive regulation in the control of gene expression in eukaryotes?
10. In sex determination in humans, female is the default state. To become male, genes must be activated that lead to the development of the testes and external male genitalia and suppression of the development of what would ultimately become the female sex organs. Many of these genes are on the Y chromosome, which is absent in genotypic (XX) females. The steroid hormone testosterone, an androgen, is involved in this process. What would you predict would happen to a genetic male (XY) fetus whose testosterone receptor had a mutation in its C-terminal domain that rendered that domain resistant to binding the androgen?
BIOLOGIA MOLEKULARNA – Lista 7 – Chromosomy i kontrola ekspresji genów u Eukaryota.
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