DNA Replication

Question 1

What does DNA occur in?

Answer 1

Semi-conservative model

Question 2

Why does DNA replicate?

Answer 2

Cells must duplicate before they can divide. This ensures that each daughter cell gets a copy of a genome, and therefore, successful inheritance of genetic traits.

Question 3

What is the backbone of DNA?

Answer 3

Sugar-Phosphate

Question 4

What is a semi-conservative model?

Answer 4

Each daughter molecule will have one old strand (derived or “conserved” from the parent molecule) and one newly made strand

Question 5

What direction does DNA occur in?

Answer 5

5’ prime –> 3’ prime end

Question 6

What is a conservation model?

Answer 6

Two parental strands rejoin after acting as templates for new strands

Question 7

What is a dispersive model?

Answer 7

each strand of both daughter molecules contains a mixture of old and newly synthesized DNA

Question 8

What is a nucleotide?

Answer 8

A nucleotide is an organic BASIC BUILDING BLOCK of nucleic acids (RNA and DNA). A nucleotide consists of a sugar molecule (either ribose in RNA or deoxyribose in DNA), attached to a phosphate group and a nitrogenous base.

Question 9

What are the bases used in DNA?

Answer 9

Adenine, Guanine, Thymine, and Cytosine

Question 10

What is on the 5’ and 3’ end of the nucleotide?

Answer 10

The phosphate group and then OH group.

Question 11

Just a reminder..

Answer 11

DNA is Anti-Parallel

Question 12

Origin of replication

Answer 12

the place where DNA replication begins, enabling a plasmid to reproduce itself as it must to survive within cells.

Question 13

Why is the origin of replication the beginning?

Answer 13

origin of replications commonly have high AT-content across all kingdoms, since repeats of adenine and thymine are easier to separate because their base stacking interactions are not as strong as those of guanine and cytosine.

Question 14

Another Reminder

Answer 14

DNA Replication is bidirectional. It is where replication is moving along in both directions from the starting point.

Occurs bidirectionally from the origin of replication (where the replication forks are).

LOOK AT DIAGRAM ON PG 16

Question 15

What are the 3 steps of DNA replication?

Answer 15

Intiation, Elongation, and Termination

Question 16

Explain three main steps in the process of DNA replication. Name the enzymes that go with each step.

Answer 16

1) Intiation: An enzyme called “helicase” untwists the DNA helix and breaks apart the nitrogen bonds between the nucleotides in either strand of DNA. This opens up the DNA & will allow DNA - polymerase to create a copy
2) Elongation: Polymerase adds DNA nucleotides to the 3’ end of the newly synthesized
3) Termination: The lagging strand is binded with DNA polymerase enzyme for in which the continous sequence of DNA molecule is synthesized

Question 17

In eukaryotic cells, is there only one origin of replication?

Answer 17

No. In eukrayotic cells, there are multiple OOR’s because

Question 18

What protein comes in to help break the bonds between the adenine and theymine?
What do they do?

Answer 18

Pre - replication protein complex.
They come in and bind onto the areas of origin and they seperate the A-T nucleotides.
Then that forms a “replication bubble”

Question 19

What protein helps to protect the “vulnerable” parental dna strands? What does it do/their purpose?

Answer 19

Single stranded binding protein
(“S.S.B.P”)

They protect the parental strands that are now single strands from nasty enzymes that want to phosphodiester bonds called, “nucleases”.

It mainly helps the parental strands from reconnecting to one another.

Question 20

Once replication bubbles are formed, there are two ends also formed which are called “replication forks”. What enzymes unwind the DNA at the end of these replication forks?

Answer 20

Helicase. Thye

Question 21

What does helicase depend on to function?

Answer 21

ATP

Question 22

What is the point of unwinding the DNA?

Answer 22

So that the strands are seperated and enzymes can use those parental strands to makenew DNA .

Question 23

LESSON:

Answer 23

When the helicase enzymes are constantly unwinding the DNA attached to the replication forks, a problem arises. The DNA starts to bunched up in front of, downstream. This creates these things called supercoils. These supercoils are bad because they eventually stop the helicase from continuing forward. So there needs to be enzymes that come in and fix the supercoils. How do we do that/what does that? There are enzymes that are called “TOPOISOMERASES”. There are type I, type II, and type IIII (collectively all do the same kinda thing). Which is what? This enzyme has two little arms. On one arm, it can go to where the area of the supercoil is, and can cut the DNA strand USING a domain of it. Which allows it to unravel. The particular name to this domain on that topoisomerase enzyme, its called a “nuclease domain”. It creates a cut or breaks the phosphodiester bond in the DNA strand (one or two), which allows it to unravel. However, yet another problem arises as the continous unraveling would cause the DNA could fragment. So to solve this, it uses the other arm, known the “ligase domain”, which not only unwinds the DNA supercoils, but also stitches it back up. NOTE: Type 1 doesn’t require any ATP to unwind the supercoils. BUT for type 2 and type 4, they do require ATP.

Question 24

MOVING ON TO ELONGATION

Answer 24

During elongation, an enzyme called DNA polymerase adds DNA nucleotides to the 3′ end of the newly synthesized polynucleotide strand. The template strand specifies which of the four DNA nucleotides (A, T, C, or G) is added at each position along the new chain.