13.2: Many proteins work together in DNA replication and repair

Question 1

Compare pro and eukaryotes

Answer 1

Prokaryotes

Single circular chromosome

1 origin of replications

Not very much protein

circular DNA

no telomeres due to circle

Eukaryote

Many linear chromosomes

Many origins of replications

a large amount of protein

linear DNA

telomeres due to linear

Question 2

Significance of new strands

Answer 2

Each of the individuals separated strands acts as a template for new strands using base pairing

Question 3

semiconservative model

Answer 3

where each of the 2 new daughter cells will have on a strand of the parent

Question 4

conservative(wrong)

Answer 4

where the parent strands end up together

Question 5

dispersive model(wrong)

Answer 5

chunks are DNA are mixed around

Question 6

Who proved the semi-conservatives model right

Answer 6

Matthew Meselson and Franklin Stahl proved that the semi-conservative model was right

Question 7

What macromolecules are involved in DNA replication ?

Answer 7

Proteins and enzymes are involved in the accurate and elegant process of DNA replication

Question 8

origins of replication

Answer 8

the replication of chromosomal DNA beginning point

Question 9

what open up replication bubbles?

Answer 9

proteins are the ones that bind and open up replication bubbles, then move in opposite directions till the strands are separated

Question 10

replication fork

Answer 10

Y shaped region where the parental strands are being unwound

Question 11

Helicases

Answer 11

enzymes that untwist the double helix at the replication forks, separate the 2 parental strands, and makes them available as template strands

Question 12

single-strand binding proteins

Answer 12

bind to the unpaired DNA strands, keeping from repairing

Question 13

Unwinding(Summary)

Answer 13

topoisomerase: smoothes out the twisted DNA helix, removes tension in the twist

1. Helicase breaks the hydrogen bonds between nucleotide bases(starts at replication bubble)
2. Two templates are exposed, revealing free nitrogenous bases on the templates
3. Single strand binding proteins – hold open DNA

Question 14

primer

Answer 14

synthesized by enzyme primase, Since DNA can be placed yet, primers are first placed

Question 15

primase

Answer 15

adds RNA nucleotides one at a time, using the other strand as a template, the new DNA strand will start to form the 3’ end of the RNA primer

Question 16

DNA polymerases(III and I)

Answer 16

catalyze the synthesis of new DNA by adding nucleotides to the 3’ end of the preexisting chain

DNA pol III adds DNA nucleotides to the RNA primer and then continues adding DNA nucleotides

Question 17

What happens when DNA pol III

Answer 17

The leaving of the pyrophosphate creates the exergonic reaction needed in order to

Question 18

Complementary base pairing(Summary)

Answer 18

1. RNA primase sets the RNA primers on predetermined nucleotide bases
2. DNA polymerase III finds the primers and sequences complementary bases to exposed template bases. Matches A-T and G-C
3. DNA polymerase III reads in the 3’ to 5’ direction, but lays down the new complementary side from 5’ to 3’. This achieves the anti-parallel aspect of the DNA helix.
4. The DNA polymerase III that reads the template from 3’ to 5’ and follows the direction of replication is called the leading strand. It is a continuous process.
5. DNA polymerase that reads the template from 3’ to 5’ but away from the direction of replication is called the lagging strand. The lagging strand is made of discontinuous segments called Okazaki fragments
6. Leading and Lagging strands are defined by replication fork

Question 19

leading strand

Answer 19

where DNA pol 3 remains in the replication fork on that template strand and adds nucleotides only using one primer

Question 20

lagging strand

Answer 20

elongates away from the replication fork

Question 21

Okazaki fragments

Answer 21

series of segments of the lagging strand

Question 22

DNA ligase

Answer 22

joins all Okazaki fragments in order to make a continuous strand, DNA pol 1 removes the primer

Question 23

DNA replication machine

Answer 23

many proteins that participate in DNA replication actually form a single large complex, a “DNA replication machine.”, it is said that DNA simply passes through this and becomes duplicated, there are large amounts of these on each cell

Question 24

What proofreads

Answer 24

DNA polymerases proofread as well when finding a mistake nucleotide, it is removed

Nuclease/DNA polymerase proofreads the complementary side of the new helix to check for mistakes, makes repairs

Question 25

mismatch repair

Answer 25

other enzymes remove and replace incorrectly paired nucleotides resulting from replication errors

Question 26

nuclease

Answer 26

an enzyme that takes out damages strand, the resulting gap is later filled with nucleotides by DNA polymerase and ligase

Question 27

Evolutionary Aspect

Answer 27

Mutations can sometimes be good, causes genetic variation

Question 28

what produces shorter DNA?

Answer 28

repeated rounds of replication produce shorter and shorter DNA molecules with uneven ends

Question 29

telomeres

Answer 29

stop chromosomes from being eroded away, or mainly delay it, can be linked to aging, its growth enzyme, telomerase, is mainly inactive in human somatic cells, repeated subunits in DNA TTAG and can resist cancer growth