BIOL 3110 Lecture Notes - Lecture 2: Central Dogma Of Molecular Biology, Dyskeratosis Congenita, Antiviral Drug

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7 Nov 2017

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The telomerase loss of function: loss of function means that you have a mutation that causes decrease in telomerase activity. Immune system gets weaker: amount of stem cells goes down, premature aging, cancer, drugs are being made to reduce the activity of telomerase. Topoisomerases: topoisomerase runs in front of helicase, topoisomerase cut strands, release tension, and join strands together, as you pull strands apart twisting tension in the strands increases. Topoisomerase i: cuts one strand at a time and allows the other strand to pass through the break, works without atp because it is doing something but brings it back to the original form. 4 fig 4-11, 4-23, 4-25: the change in number of links per turn is n+o -1, change by a factor of 1. If you have 8 links it will be 9 and if there are 12 links there will be 13. It breaks one strand at a time but makes a connection always.

Related Questions

Which of the following best describes why ends of linear chromosomes cannot be replicated comepletely?

A) Telomeres are heterochromatin; therefore, no replication of the telomeres even occurs

B) Nucleotides on the 5' end of a DNA strand (template) cannot be replicated because there is no binding site for a primer, which is required by DNA polymerases

C) The 5' end of a DNA strand (template) cannot be replicated because DNA polymerase cannot add nucleotides on to the 5' end

D) Nucleotides on the 3' end of a DNA strand (template) cannot be replicate becaue there is no binding site for a primer, which is required by DNA polymerases

What are the advantages of recombination? What are the disadvantages? Under what kinds of ecological conditions (stable environment, high predation rates, exposure to rapidly evolving parasites, etc.) would you expect to favor one, or the other?

Suppose you found a region of a genome in a vertebrate that was quite large (say, 10 million base pairs) that had an extremely low recombination rate. Suggest a reason why it might be advantageous to not recombine the genes in that genomic region.

How do prokaryotes distinguish the newly synthesized strand from the old template strand? Why donât eukaryotes use the same mechanism?

What is methylation used for in prokaryotes? In eukaryotes?

What happens if mismatch repair occurs shortly after replication? How does it know which mismatched, normal base is incorrect? What happens if mismatch repair occurs long after replication has occurred?

Why does uracil DNA glycosylase have so an easier task to perform than thymine DNA glycosylase?

Describe the steps that occur following uracil DNA glycosylase activity. What needs to happen; what enzymes are involved?

What do x-rays do to DNA? What does UV radiation do? What do microwaves do?

Is there a safe minimum dose of radiation?

Why is telomerase turned off in human somatic cells? Is it turned off in mouse somatic cells? Would you expect it to be turned off in elephants? Would you expect elephants to have high cancer rates compared to mice?

Where is telomerase necessary? Is it on the leading, or lagging strand, or both? Why donât bacteria need telomerase?

Why is microsatellite instability used by physicians to measure problems with mismatch repair?

In addition to identifying the genetic material, the experiments of Avery, MacLeod, and McCarty with different strains of Streptococcus pneumoniae demonstrated that

	DNA is a double helix.
	DNA may be taken up by bacterial cells and be active.
	DNA is present in bacteriophage T2.
	eukaryotic cells may be genetically transformed.
	DNA binds to the cell wall of the bacterium.

In order to show that DNA in cell extracts is responsible for genetic transformation in Streptococcus pneumoniae, important corroborating evidence should indicate that _______ also destroy transforming activity.

	temperatures high enough to kill cells
	enzymes that hydrolyze proteins
	enzymes that hydrolyze DNA
	enzymes that hydrolyze polysaccharides
	enzymes that hydrolyze RNA

Based on what you have learned about the experiments conducted by Griffith and Avery and colleagues with bacteria, which of the following would result in transformation of living R cells?

	Pure RNA from S cells
	Cell-membrane extracts from S cells
	A mixture of pure RNA and protein from S cells
	Cell-free extracts from S cells
	Pure protein from S cells

A-T base pairs in a DNA double helix

	form three hydrogen bonds with each other.
	are more heat-stable than G-C base pairs.
	are of a substantially different length than G-C base pairs.
	are not accessible to DNA binding proteins.
	are chemically distinct from G-C base pairs.

If 23 percent of the bases in a sample of double-stranded DNA are adenine, what percentage of the bases are uracil?

	27
	50
	0
	73
	23

The uniform diameter of the DNA structure provides evidence for

	antiparallel DNA strands.
	a right-handed helix.
	a double-stranded helix.
	3â² end phosphorylation.
	purineâpyrimidine pairing.

If a sequence of one strand of DNA is 5â²-TGACTATC-3â², what is the complementary strand?

	5â²-ACTGATAG-3â²
	3â²-TGACTATC-5â²
	3â²-ACTGATAG-5â²
	3â²-ACTGATAG-3â²
	5â²-TGACTATC-3â²

What structural aspect of the DNA facilitates dissociation of the two DNA strands for replication?

	3â² end phosphorylation
	Purineâpyrimidine pairing
	Antiparallel DNA strands
	Covalent bonds between sugars and phosphate groups
	Hydrogen bonding between paired bases

If the MeselsonâStahl density gradient experiment had resulted in two bands of DNA molecules after only one round of replication, one containing only ¹⁵N and the second only ¹⁴N, this result would have indicated that replication was

	unidirectional.
	dispersive.
	conservative.
	bidirectional.
	semiconservative.

10.

The nucleoside analogue acyclovir, which is used to treat herpes simplex virus (HSV) infections, lacks a 3â² hydroxyl group (âOH). Predict what will happen if the host cell DNA polymerase incorporates a molecule of acyclovir into an elongating strand of HSV DNA.

	The replication complex will no longer bind to origins of replication.
	The DNA polymerase will only incorporate acyclovir molecules.
	Acyclovir will bind single-strand binding proteins.
	DNA polymerase will not be able to link a successive nucleotide.
	Acyclovir will block the activity of the DNA helicase.

11.

Which of the following does not demonstrate the stability of the DNA double helix?

	Single-strand binding proteins are required to keep the strands apart.
	Paired bases form hydrogen bonds.
	High temperatures are required to denature it.
	DNA synthesis requires energy.
	DNA helicases require ATP.

12.

What effect would a primase inhibitor have on DNA replication?

	DNA polymerase would not be able to add bases to the DNA.
	Primase would be blocked from joining the DNA replication complex.
	Primase would not be able to provide primers for DNA polymerases.
	DNA polymerase would not be able to use DNA as a template.
	There would be no effect on DNA replication.

13.

To replicate their DNA in a timely manner, most eukaryotic chromosomes

	normally have uncoiled DNA.
	have multiple origins of replication.
	contain linear molecules of single-stranded DNA.
	have two replication forks that move in the same direction.
	are composed entirely of DNA.

14.

Which statement about DNA replication is false?

	Okazaki fragments are synthesized as parts of the leading strand.
	Error rates for DNA replication are reduced by proofreading of the DNA polymerase.
	The sliding clamp increases the rate of DNA synthesis.
	Replication forks represent areas of active DNA synthesis on the chromosomes.
	Ligases and polymerases function in the vicinity of replication forks.

15.

In many eukaryotes, there are repetitive sequences called telomeres at the ends of chromosomes. After successive rounds of DNA replication, the _______ strand becomes shorter. In some cells, an enzyme called _______ repairs the shortened strand.

	leading; telomerase
	lagging; telomerase
	lagging; DNA polymerase I
	leading; DNA polymerase I
	leading; replicase

16.

A researcher studies normal human fibroblast cells. They can be maintained in culture but die off after about 30 cell generations. Unexpectedly, a colony of cells continues to survive and divide past 30 generations. Which scenario is most likely true for these cells?

	DNA polymerase is constantly active.
	Primase is able to extend the telomeres.
	The mismatch repair system is extra efficient.
	The telomerase gene is being expressed.
	The cells do not need the ends of their chromosomes.

17.

If DNA polymerase III introduces an incorrect nucleotide, what is the first corrective action made by the DNA repair system?

	The replication complex excises the incorrect nucleotide.
	The excision repair proteins remove the incorrect nucleotide.
	The mismatch repair system scans for base-pairing mismatches.
	There is no correction, because nucleotide errors by DNA polymerases are not repaired.
	DNA ligase connects the correct nucleotide.

18.

Choose the correct order of the following four events in the excision repair of DNA:
(1) Base-paired DNA is made complementary to the template.
(2) Damaged bases are recognized.
(3) DNA ligase seals the new strand to existing DNA.
(4) Part of a single strand is excised.

	1, 2, 3, 4
	2, 1, 3, 4
	3, 4, 2, 1
	2, 4, 1, 3
	4, 2, 3, 1

19.

Six complete cycles of PCR should result in a _______-fold increase in the amount of DNA.

	64
	32
	12
	128
	6

20.

When double-stranded DNA is heated to temperatures above 90Â°C, it denatures. Denaturation is a process that

	breaks covalent bonds.
	hydrolyzes DNA.
	separates double-stranded DNA into two single strands.
	causes new hydrogen bonds to form.
	irreversibly destroys the double helical structure.

BIOL 3110 Lecture Notes - Lecture 2: Central Dogma Of Molecular Biology, Dyskeratosis Congenita, Antiviral Drug

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