Lecture 5

Question 1

transforming principle

Answer 1

Transformation occurs when one bacterium picks up free-floating DNA and incorporates it into its own genome– the principle was that something caused the bacteria to transform from one type to another

Question 2

Briefly describe the methods of Avery’s experiments (DNA as Molecule of Heredity)

Answer 2

added protease, RNAse, and DNAse to 3 different flasks with bacteria, transformation occurred in the protease and RNAse treatments but no transformation in the DNAse flask

Question 3

What is the ultimate purpose of DNA?

Answer 3

Information storage and transfer

Question 4

DNA polymerase can only add to the _____.

Answer 4

3’ end– must have a preexisting -OH gropu to add to

Question 5

major groove vs. minor groove

Answer 5

major groove is where the backbones are far apart, minor groove where they are close together

Question 6

Which direction does proofreading occur in?

Answer 6

3’-5’ by DNA Pol I

Question 7

endonuclease

Answer 7

cleaves the phosphodiester bonds in the middle of the DNA strand– large component of restriction enzymes and recombinant DNA technology

Question 8

exonuclease

Answer 8

hydrolyze phosphodiester bonds at the 3’ or 5’ end of the DNA

Question 9

lagging vs. leading strand

Answer 9

lagging strand is constantly falling off, synthesizing, falling off, synthesizing– leading strand synthesizes continuously

Question 10

At every origin there are ______.

Answer 10

2 replication forks– creates a bubble and forks grow in both directions

(only one origin in bacteria because they are circular)

Question 11

helicase

Answer 11

enzyme that unzips DNA helix

Question 12

primase

Answer 12

synthesizes an RNA primer to be used for DNA synthesis (one primer for leading strand, one per every Okazaki fragment for lagging)

Question 13

DNA Polymerase III

Answer 13

Adds bases to new DNA chain, proofreads for mistakes

Question 14

DNA Polymerase I

Answer 14

Removes RNA primers, replaces gaps with Okazaki fragments with the correct nucleotides, repairs mismatched bases

Question 15

ligase

Answer 15

final binding of nicks in DNA during synthesis and repair

Question 16

topoisomerase

Answer 16

adds a species dependent telomere repeat sequence to the 3’ end of telomeres to help counteract overhanging at 3’– not usually active in somatic cells but is active in germ cells