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ANHB1101 Lecture Notes - Lecture 26: Okazaki Fragments, Dna Ligase, Nucleic Acid Double Helix

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bronzeswan753
5 Sep 2018
School
UWA
Department
Anatomy and Human Biology/Anatomy, Physiology and Human Biology
Course
ANHB1101
Professor
Fiona O'Shea

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Document Summary

G0 = cell cycle rest g1 = cell contents/organelle duplicated. S = chromosomes duplicated (from single chromatids to chromosomes connected with a centromere) G2 = cell double check everything is correctly prepared + checks for errors mitosis + cytokinesis. Double helix held together by cohesins in mitosis/meiosis. Check points in mitosis - checks if cellular environment is correct for the particular mitotic process at that point. Dna polymerase moves from 5" to 3" end. Primer required (starting template for the dna polymerase). Helicase unwinds and rewinds dna. (creates replication fork and work here when unwinding). leading strand is extended continuously. lagging strand is extended discontinuously, by addition of short okazaki fragments. Okazaki fragments - due to having to move from the 3" to 5" end. Joined later by dna ligase. is occurring all the way along the dna i. e not just in one spot at one time. 3" to 5" exonuclease activity - reduces errors.

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Related Questions

1. 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.
2. 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
3. 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
4. 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.
5. 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
6. The uniform diameter of the DNA structure provides evidence for
antiparallel DNA strands.
a right-handed helix.
a double-stranded helix.
3′ end phosphorylation.
purine–pyrimidine pairing.
7. If a sequence of one strand of DNA is 5′-TGACTATC-3′, what is the complementary strand?
5′-ACTGATAG-3′
3′-TGACTATC-5′
3′-ACTGATAG-5′
3′-ACTGATAG-3′
5′-TGACTATC-3′
8. What structural aspect of the DNA facilitates dissociation of the two DNA strands for replication?
3′ end phosphorylation
Purine–pyrimidine pairing
Antiparallel DNA strands
Covalent bonds between sugars and phosphate groups
Hydrogen bonding between paired bases
9. If the Meselson–Stahl 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 3′ hydroxyl group (–OH). 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 90°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.

1)What experiment was performed that allowed for scientists to finally agree that DNA is the genetic material within living organisms?

a.Understand the materials and scientific techniques used to come to this result.

2)What group of experiments led to the discovery of the mechanism used in DNA replication?

a.Understand the materials and scientific techniques used to come to this result.

i.What is a cesium chloride gradient?

ii.Where do 14N and 15N respectively fall along this gradient?

b.The results revealed that DNA replicates using which of the three proposed models?

i. Describe the mechanism of each model.

3)What is the role of the following proteins in DNA replication?

a.Helicase

b.Single strand binding proteins

c.Topoisomerase

d.DNA polymerase III

e.DNA polymerase I

f.Primase

g.Ligase

4)What extra steps are taken to be sure the lagging strand does not shorten each time DNA is replicated?

a.What is the role of telomerase in these “steps”?

5)In DNA repair, which enzyme has “proof-reading” capabilities?

1)Which type of cells within our bodies use mitosis to reproduce?

2)Does mitosis create a cell that is different or the same as the parent cell undergoing division?

3)Describe the DNA found in sister chromatids.

4)Describe the DNA found in homologous chromosomes.

5)What occurs during the following stages of the cell cycle?

a.G1 Phase

b.S Phase

c.G2 Phase

d.M Phase

What are the phases of mitosis? What events occur in each phase?

1)Does mitosis separate homologous chromosomes, sister chromatids, or both?

2)What is cytokinesis?

a.Which fibers of the cytoskeleton contract to pinch parent and daughter cells apart from one another in animals?

b.How do microtubules move chromosomes to the two poles of a dividing cell?

3)How are centrioles involved in this process?

a.How do plants form two complete cells during cytokinesis?

4)How do bacterial cells reproduce?

5)The cell cycle is controlled at “checkpoints”. What occurs at each of the following checkpoints?

a.G1 Checkpoint

b.G2 Checkpoint

c.M Checkpoint

6)How do cyclin and cdk act to control the G2 checkpoint?

7)If presented with the schematic of the M checkpoint, you should be able to explain perturbations to the system as well as if the cell will divide or stall at metaphase.

8)Cancerous cells form when the cell cycle checkpoints do not function correctly and continues to divide even though it is damaged in some way. How does the protein p53 function to keep these cells from dividing?

9)Normal cells follow certain rules of growth that cancerous cells do not follow. What are these rules (provide a short definition for each as well)?

10)What is the difference between a benign tumor and a malignant tumor?

Question 11 options:

A condition characterized by the growth of endometrial cells in areas other than the endometrium is called

Question 12

A standard screening test for cervical cancer is called

Question 13

The period of prenatal development in which the basic parts of the organ systems are formed is the

Question 14 options:

Detection of

Spell check is used by pregnancy test kits to detect the early stages of pregnancy.

Question 15

The actual gene sequence governing the expression of a trait is called a

Spell check , whereas the physical expression of this trait is the PHENOTYPE , which can also be defined as the physical expression of a gene.

Question 16

Down syndrome is a disorder where a person has an chromosome 21.

Question

A picture of all chromosomes taken in metaphase and used for analysis is called a

Question 18

A pregnancy where the fertilized egg implants in an area other than the uterus is called

Question

The basic building blocks of DNA are called

Question 20

Monosomy of the X chromosome characterized by a short stocky neck, underdeveloped secondary sexual characteristics, and infertility is called

syndrome.

Question 21

A deletion of the short arm of chromosome 5 with a typical cry that resembles a meowing cat characterize

Question 22

A serious psychological disorder characterized by the fear of becoming obese is called

Question 23

Diffusion of gases between capillary beds and tissues is called respiration.

Question 24

The destruction of alveoli by irritants such as cigarette smoke and agricultural dust is found in a disorder called

Question 25

Of the three types of skin cancer which are the most likely to metastasize

Question 25 options:

Melanoma

Squamous cell carcinoma

Basal cell carcinoma

All of the above have equal ability to metastasize

Question 26

Cancer of this organ/gland causes the most deaths annually

Question 26 options:

Lung

Breast

Prostate

Bladder

Question 27

The correct order of stages of the cell cycle that a new cell will go through immediately after being produced by mitosis is

Question 27 options:

S, G1, G2, M

G1, G2, M, S

G1, S, G2, M

M, G1, S, G2

Question 28

What is the purpose of DNA replication

Question 28 options:

To copy the information in a gene so that extra protein synthesis can be done

To make an RNA copy of the gene

To provide the cell with extra DNA in case the original gets damaged

To ensure that two cells produced by mitosis have the same genetic information as the parent cell

Question 29

Which of the following is not a function and/or advantage of mitosis

Question 29 options:

It can repair damaged tissue

Growth takes place through mitosis

It can replace old or damaged cells

All of the above are functions and/or advantages

Question 30

Which stage of the cell cycle occurs just after mitosis

Question 30 options:

G1

G2

S

Prophase

Save

Question 31 (1.5 points) Question 31 Unsaved

DNA replication is completed by the end of

Question 31 options:

Prophase

G1

S phase

G2

Question 32

Which of the following is NOT true of DNA

Question 32 options:

Generally double stranded

Stores the cell genetic information

Replicated by DNA polymerase

Contains A, C, U, and G

Question 33

These cell may enter G0 of the cell cycle permanently

Question 33 options:

Hepatocytes

Transformed cells

Neurons

Cells in the digestive system

Question 34

When a primary spermatocyte, goes through meiosis, how many mature sperm will be produced

Question 34 options:

1

2

3

4

Question 35

When a primary oocyte goes through meiosis, how many mature eggs will be produced

Question 35 options:

1

2

3

4