CSB351Y1 Lecture 13: Lecture 13

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redskunk879

15 Feb 2012

School

UTSG

Department

Cell and Systems Biology

Course

CSB351Y1

Professor

Mounir Abou Haidar

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Document Summary

Viroids are small circular rna, have no coding capacity, but are capable of replication. They use rna polymerase, a dna directed rna polymerase in the nucleus for their replication. Viroids that have ribozymes, replicate in chloroplasts; small amount, not in nucleus; majority are in nucleus. Usually they have a structure that is ds rna, that has some mismatches; looks like ds, this is diagram, shows lots of bubbles, they don"t match. That structure that looks like ds, is very important for the life of those viroids. They have to have an origin of replication, dna dep rna polymerase of the cell has to recognize an origin of replication. 20 types of viroids, did a study, most have this conserved sequence, nothing to memorize, in the middle, then have conserved domains, which are circular, but then makes this kind of odd shape due to mis-match base pairing.

Related Questions

Multiple choice.

1.Origins of replication...

A. occur at many sites on bacterial and human chromosomes

B. contain one replication fork each where the daughter stands are being sythesized

C. initiate replication in a uni-directional manner

D. result in bubbles opened by helicases

E. occur at one site per chromosome

2.Telomerase...

A. is important for the replication of circular chromosomes

B. is important for the replication of linear chromosomes

C. carries a template in the form of a DNA molecule

D. sythesizes RNA primers

E. both the 1st and 2nd option are correct

3.What are topoisomerases?

A.Enzymes that lay down an RNA primer during DNA synthesis.

B.The ends of the chromosomes.

C. Proteins that unwind DNA.

D. A strain of mice.

4.Which enzyme produces the first piece of nucleic acid synthesized in DNA replication?

A. Primase

B. DNA polymerase

C.ORC

D. DNA ligase

5. Which of the following does not contribute to the mutagenesis of our DNA?

		A. alterations to bases (nucleotides) that change their hydrogen bonding characteristics
		B. passing on of mismatched DNA into daughter cells
		C. inefficiency of MutS to recognize errors in base pairing
		D. DNA polymerase slipping during synthesis and creating insertions or deletions
		E. DNA polymerase erroneously synthesizing DNA in the reverse direction during S phase

Which of the following is correct about DNA replication? A. Replication begins from one end of the molecule, and ends at the other end. B. A type of RNA polymerase is the enzyme that lays down the first nucleotide of the daughter strand. C. Replication occurs in one chromosome at a time. D. DNA polymerase III and the primase have opposite directions of functions. E. At the end of replication, two DNA molecules are present- the original molecule, and a newly synthesized DNA molecule.

rosewoodchuck649

An individual inherits two defective copies of the MLH1 gene, a protein involved in mismatch repair of DNA during its replication. What do you predict will be the consequences of deficient mismatch repair upon DNA replication?

a. The fidelity of DNA polymerase activity will be decreased.

b. Mismatched nucleotides will no longer be detected by the replication complex.

c. Ligase will not be able to repair nicks in the DNA.

d. There will be a higher frequency of nucleotides damaged by external agents.

e. A higher frequency of mutations will become fixed in the newly synthesized strand.

CSB351Y1 Lecture 13: Lecture 13

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