CH 12 DNA Replication and Manipulation Reading Guide

Question 1

Explain semi conservative and conservative DNA?

Answer 1

Semi conservative: one strand of the newly formed DNA will be from the parent and another strand will be brand newConservative both strands are from the parents no new strand is created

Question 2

What method did me seldom and stahl up to identify parental and newly synthesized DNA strands?

Answer 2

They labeled the different strands with different isotopes of nitrogen

Question 3

Explain the three main steps of the modelson and stahl experiment?

Answer 3

1 both strands of DNA are labeled with heavy nitrogen which forms a band of heavy DNA2 after one round of replication one strand contains heavy nitrogen and one strand contains light nitrogen therefore net lighter3. After two rounds of replication two strand of light nitrogen and one stand of heavy and one strand of light similar to step 2

Question 4

How are the two daughter strands different after replication?

Answer 4

There anti parallel to one another

Question 5

What is the enzyme called that is required to catalyze the addition of new nucleotides? Do they synthesize DNA from an existing template.

Answer 5

DNA polymeraseYes

Question 6

Define leading strand

Answer 6

The daughter strand that has its 3’ end pointing towards the replication fork

Question 7

Define lagging strand

Answer 7

The daughter strand that has its 3’ end pointing away from the replication fork

Question 8

Define Okazaki fragments

Answer 8

Short pieces found within the lagging strand

Question 9

Define a primer

Answer 9

Short stretch of RNA that serves as the starting point for a strand of DNA

Question 10

What type of enzyme is primase?

Answer 10

A type of RNA polymerase

Question 11

Why does DNA polymerase require a primer in order to do its job?

Answer 11

So that it knows where to start copying

Question 12

What happens to DNA primers during the process of DNA replication?

Answer 12

Gets replaced by DNA nucleotides

Question 13

What do DNA ligases do?

Answer 13

Joins the fragments of DNA together

Question 14

Define proofreading

Answer 14

A process when DNA polymerase correct there own copying errors

Question 15

How good is DNA polymerase at finding errors

Answer 15

99%

Question 16

Define a mutation in the context of DNA polymerase?

Answer 16

When mistakes slip past the proofreading process Some mistakes in coding may cause harmful changes to the genetic code

Question 17

What is the function of helicase?

Answer 17

To unwind the parental double helix at the replication fork

Question 18

What do topoisomerases do?

Answer 18

Removes stress associated wight the unwinding at the replication fork

Question 19

What do single stranded binding proteins do?

Answer 19

Bind the resulting single stranded regions of DNA to prevent the template strands from coming back together

Question 20

How are the deoxyribose sugars linked together in a DNA strand?

Answer 20

Phosphate group