DNA + DNA Replication

Question 1

Base Pairing Rules of DNA

Answer 1

Adenine bonds to Thymine in a double hydrogen bond

Cytosine bonds to Guanine with triple

Question 2

Steps of DNA Replication

Answer 2

1. The double helix opens up or “unzips”
2. free-floating nucleotides line up with the matching nucleotides on the dna strand
3. The free-floating nucleotides physically connect to the DNA strand
4. a new strand of DNA is formed along the open strands
5. Two complete and identical DNA helices are created
6. Cell division can occur!

Question 3

Helicase Enzyme: What does it do?

Answer 3

Helicase unwinds the helix and separates the strands, or “unzips” the DNA
It breaks through the hydrogen bonds that hold the nucleotides together

Question 4

Primase Enzyme: What does it do?

Answer 4

It makes the primer that lets the DNA polymerase know where to go

Question 5

Ligase enzyme: What does it do?

Answer 5

Ligase seals up the spots that other enzymes miss,
it seals up the gaps between okazaki fragments

Question 6

why do we call DNA replication semi-conservative?

Answer 6

Because each new DNA strand that results from DNA replication has one old original strand, and one new strand

Question 7

Difference between leading + lagging strand?

Answer 7

DNA is anti-parallel because the two strands do not go in the same direction,
one strand goes 5’ to 3’ and the other strand goes 3’ to 5’

The DNA polymerase can only build the DNA from 5’ to 3’ and the dna that runs from 5’ to 3’ towards where the dna is being separated by helicase is the leading strand

the lagging strand is the strand that runs 3’ to 5’ towards where helicase is separating it and this causes the polymerase to make okazaki fragments

Question 8

how do you determine if a DNA strand is 5’ to 3’ or 3’ to 5’

Answer 8

The sugar in DNA is part of the backbone of DNA and it has carbons
the carbons on the sugar are numbered after the oxygen in a clockwise direction

Question 9

Functions of DNA polymerase:

Answer 9

• adds matching nucleotides to the ones on the strands that are separated by helicase
• ## rarely makes mistakes

Question 10

What are cell cycle regulators?

Answer 10

Proteins that control the progression of the cell cycle

they can inhibit the cell cycle

and stimulate the cell cycle

Question 11

What are proto-oncogenes

Answer 11

the genes that code the stimulatory proteins in the cell cycle (EX: Cyclins)

Question 12

Role of Cyclins and Kinases

Answer 12

Cyclins bond to enzymes called kinases and then the kinases activate other enzymes and proteins necessary for cell cycle control

Question 13

what happens if proto oncogenes and tumor suppressor genes are mutated

Answer 13

the cell repeatedly divides even if it should not