BIO130H1 Lecture Notes - Lecture 7: Telomerase Rna Component, Okazaki Fragments, Dna Replication

109 views5 pages

melodyli

12 Jul 2018

School

Department

Course

Professor

For unlimited access to Class Notes, a Class+ subscription is required.

ash-mr18 and 40043 others unlocked

BIO130H1 Full Course Notes

Verified Note

31 documents

Document Summary

Okazaki f(cid:396)ag(cid:373)e(cid:374)ts at the (cid:1007)" e(cid:374)d to extend onto to fill in for the primer: nucleases in the cell that process the. In the majority of eukaryotes, this problem is solved by having repetitive. Dna sequences at the ends of the chromosomes, which are called telomeres. Telomerase to the rescue: the (cid:396)epetiti(cid:448)e se(cid:395)ue(cid:374)(cid:272)e that is added to the (cid:1007)" end of parental strand (i. e. , lagging strand template) is determined by rna template in telomerase, uses an rna template to make a dna complementary/antiparallel copy. Lo(cid:374)ge(cid:396) (cid:1007)" e(cid:374)ds are protected by comes and tucks in to base pair with the middle of the blue strand. Topoisomerase i: single-stranded break, allows dna to rotate around the sugar-po4 backbone of one strand, no atp required. Topoisomerase ii: double-stranded break, allows one double-stranded helix to pass through another, requires atp. The high fidelity of dna replication: rna polymerases typically have an error rate of about 1 in 104, dna polymerase about 1 in.

Related Questions

Double check to see if I got these right? 3 questions

Some Processes Involved in DNA Replication

1.The replication origin is identified.

2 DNA primase builds RNA primer.

3Okazaki fragments are spliced by DNA ligase.

4Helicases bind and uncoil the DNA double helix.

5 RNA primer is the starting point for DNA polymerase.

6 DNA replication ends at the telomere where DNA codes fortermination.

7 DNA polymerase adds complementary nucleotides in the 5' to 3'direction in short segments called Okazaki fragments.

The sequence in which the events numbered above occur during DNAreplication of the lagging strand: Number 1 - 7 in order.

I put: 1,4,2,5,7,3,6

__________________Question 2:

Some Functions of Enzymes

Build DNA strands
Build RNA primers
Build mRNA strand
Cleave DNA strands
Splice Okazaki fragments

Enzyme:
Helicase :4
DNA ligase :5
RNA primase :1
RNA polymerase :3
DNA polymerase:2

Question 3:

like mRNA, tRNA has a ribose sugar, U instead of T, and issingle stranded. Unlike mRNA, which remains a long single strand ofnucleotides, tRNA folds so that some areas pair up.

The resulting structure has an anticodon on one end and a site foran amino acid to attach on the other end. There is basecomplementarity (A pairs with U and G pairs with C) between an mRNAcodon and tRNA anticodon.

If the amino acid tyrosine attaches to a tRNA, which of thefollowing anticodons could be at the opposite end of the tRNAmolecule?

Select one:

a. ATA and ATG

b. UAU and UAC

c. AUA and AUG

d. AGA and AGU

I picked B.

purpleturtle13

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.

Multiply questions here

Q2. What is the consequence of chromosome inversion on meiosis? (work on a zygote with one normal chromosome and one chromosome with an inversion)

Q3. Search the web or read the textbook. Find a disease that is caused by translocation. What kind of translocation causes the disease?

Q4. Briefly explain how downâs syndrome or other trisomy is generated (3 sentences should be enough for you to explain this clearly)

Q5. I mutated a culture of wild type E. coli cells and wanted to isolate mutants that are unable to synthesize uracil (a nitrogen base in RNA). How can I achieve my goal? (try to finish your answer in 2-3 sentences)

Q6. For the ura- mutant isolated in Q5, I want to convert it to URA+ by transformation. Please tell me how I can achive this transformation with 3 SIMPLE sentences

Q7. What is the difference and relationship between an Hfr cell and an F+ cell?

Q8. I want to set up a mating between an Hfr strain and an F- (ade- his- bio-) strain and detect bio+ recombinant. Please design the experiment for me. (What genotype for Hfr do you need to choose? How will you select your recombinant? etc).

Q9. I want to use phage T2 to transducer the wild type ADE2 gene from the wild type E. coli strain to an ade2- E. coli mutant. How can I do this experimentally? (please briefly describe the approach, not experimental details such as incubation for 10 min, etc).

Q10. We talked about recombination in both eukaryotes and prokaryotes. Are there any differences in these two recombination ? (what are they if there are?)

Q11. Whose (or what) experiment proves that DNA is the genetic material?

Q12. What knowledge did Watson and Crick use in constructing the DNA model?

Q13. How does the double helix model support the three major functions of genetic materials?

Q14. What is the major chemical force that holds DNA and histone together? Hydrogen bonds

Q15. If I label E. coli cells in an N15 medium overnight and chase cells in an N14 medium for 2 generations, what fraction of cells still carry the N15 label?

Q16. If a 1000 kilobase fragment of DNA has five evenly spaced replication origins and DNA polymerase moves at 1 kilobase per second, how many seconds will a cell take to produce two daughter molecules?

Q17. DNA polymerases catalyze the polymerization of nucleotides. Use the formula for enzyme catalyzed reaction (see the example) to describe DNA polymerases. Example: Enzyme Substrate A + substrate B -------------------ï product c + product D Q8. During DNA replication, what is the direction of the growing strand?

Q18. For DNA synthesis in cells, why are there a leading strand and a lagging strand?

Q19. The following is the DNA sequence of a template strand. If the primase begins to synthesize primers from the middle âgâ, what will the primer sequence be? (assuming the primer can be 8 nucleotides long) 5â GACTCTAgGACTCCT 3â

Q20. Both DNA polymerase I and DNA polymerase III synthesize DNA during DNA replication. Please state the different roles they played during DNA replication.