Chapter 8

Question 1

What is dna replication?

Answer 1

Is semiconservatiev

Question 2

What stage in eukaryotes does dna replication take place in?

Answer 2

The S phase

Question 3

What is the organization of the genome in prokaryotes ?

Answer 3

One circular chromosome

Question 4

What is organization of the genome eukaryotes

Answer 4

There are several linear chromosomes

Question 5

Where does replication begin ?

Answer 5

At special sites along the dna called origin of replication
Replication occurs bidirectionally

Question 6

How many Origins of replication are there in prokaryotes and eukaryotes

Answer 6

Prokaryotes = one origin
Eukaryotes multiple origins

Question 7

What is the first step in DNA replication ?

Answer 7

Proteins recognize the ori , bind to the dna and start to unwind it forming a replication bubble

Question 8

What is at the end of each replication bubble

Answer 8

The replication fork

Question 9

What is helicase ?

Answer 9

A protein that binds at the replication for , unwinding the DNA strands
The helicase moves down the DNA as replication continues

Question 10

What is the single stranded dna binding proteins ?

Answer 10

These proteins bind to the single stranded dna and keep the strands separated and stabilize the single stranded DNA

Question 11

What is the topoisomerase (dna gyrase)

Answer 11

Binds to the dna nad helps to relieve the torsional stress by breaking , swivelling and redoing the dna strands

Question 12

What is primase?

Answer 12

Synthesizes an rna primer at 5 prime end of the leading strand and at the 5 prime end of each Okazaki fragment of the lagging strand

Question 13

DNA pol iii

Answer 13

Using parental dna as a template , synthesizes new dna strand by adding nucleotides to an rna primer or pre existing dna strand

Question 14

What is dna pol i

Answer 14

Removes rna nucleotides of primer from 5 ‘ end and replaces them with dna nucleotides

Question 15

What is dna ligase?

Answer 15

Joins Okazaki fragments of lagging strand
On the leading strand it Joins the 3 prime end of dna that replaces the primer to rest of the leading strand

Question 16

What direction does dna polymerase synthesize in ?

Answer 16

5’ to the 3’ direction
No KNOWN dna polymerase can synthesize DNA de novo
DNA polymerase requires a free 3 PRIME OH GROUP

Question 17

How does dna polymerase make/elongate a new strand ?

Answer 17

DNA polymerase catalyses the formation of a phosphodiester bond between the 3’-oh group of the first phosphate of the incoming nucleotide
DNA polymerase uses DNTPS as the substrate

Question 18

What are three things dna polymerase needs to synthesize a complementary strand of dna ?

Answer 18

Template that will direct the synthesis of a complementary strand of dna
Primer to provide a free 3’-OH group to which nucleotides can be added on to
Deoxynucleotide triphosphate

Question 19

Why does DNA need a primer ?

Answer 19

Because dna polymerase can’t make a new strand of DNA from the template strand , it needs something to add nucleotides on it

Question 20

What is a leading strand ?

Answer 20

As chains are elongating one is being replicated in a continuous manner

Question 21

What is the lagging strand?

Answer 21

Chain being replicated in a discontinuous manner
Segments of DNA that make up the lagging strand are called Okazaki fragment S