Chapter Three: DNA, RNA

Question 1

Nitrogenous Bases (5)

Answer 1

1. Adenine
2. Guanine
3. Cytosine
4. Thymine (DNA)
5. Uracil (RNA)

Question 2

What are the three components of a nucleotide?

Answer 2

1. A phosphate group
2. A deoxyribose sugar
3. A nitrogen-containing base

Question 3

Purine

Answer 3

Double-ring base

Adenine, guanine

Question 4

Pyrimidine

Answer 4

Single-ring bases

Cytosine, thymine, uracil

Question 5

Leading Strand

Answer 5

Strand of DNA moving from the 5’ to 3’ end, named after the numbering of carbons in the deoxyribose sugar.

Question 6

Lagging Strand

Answer 6

Section of DNA that moves from the 3’ to 5’ direction, named after the numbering of carbons in the deoxyribose sugar.

Question 7

Fredrich Miescher

Answer 7

Isolated the nuclei of white blood cells and extracted an acidic molecule called nuclein (DNA)

Question 8

Fredrick Griffith

Answer 8

• Experimented with two strains of bacteria which affected mice. (Pathogenic and non-pathogenic)
• the pathogenic bacteria could cause the non-pathogenic bacteria to also be lethal
• established that either DNA, RNA, or proteins were the material of heredity

Question 9

Avery, MacLeod, McCarty

Answer 9

• built on Griffith’s work by identifying which molecule was causing the transformation
• subjected the heat-killed pathogenic strain to one of three enzymes: One that killed proteins, DNA, or RNA
• the DNA destroying enzyme did not allow the heat-killed pathogenic strain to become lethal

Question 10

Hershey and Chase

Answer 10

• T2 bacteriophages tracked by either the 35S isotope (for proteins) or the 32P isotope (for DNA)
• Tracked which isotope was injected into the bacteria from the virus: the 32P

Question 11

Erwin Chargaff

Answer 11

-studied nucleic acids and their composition

Chargaff’s rule: % composition of A=T, % composition of C=G

Question 12

Rosalind Franklin

Answer 12

• used x-ray diffraction to analyze DNA samples
• determined DNA’s helical structure, that the hydrogen bonds are on the inside of the molecule, and that the sugar-phosphate backbone is on the outside

Question 13

Watson and Crick

Answer 13

• worked on a description of the DNA structure:
• “handrail - ladder” illustration
• The distance between the sugar-phosphate backbones remain constant

Question 14

Semi-conservative Model

Answer 14

DNA replication that results in a hybrid molecule of one new strand and one old strand.

Question 15

Meselson and Stahl

Answer 15

Proved the semi-conservative model of DNA replication by using nitrogen isotopes to label the old and new DNA during replication.

Question 16

Replication: Initiation

Answer 16

• Unwinding starts at a specific nucleotide sequence called the origin of replication
• helicase enzymes cleave the hydrogen bonds between bases
• Topoisomerase ll (in prokaryotes) relieves strain on the double helix that is generated from unwinding.
• Replication bubble forms

Question 17

Replication: Elongation part l

Question 18

Replication: Elongation part ll

Answer 18

• lagging strand formed in short segments away from replication fork.
• primase synthesizes RNA primer for DNA polymerase lll to extend the strand by creating Okazaki fragments.
• DNA polymerase l removes primers
• DNA ligase joins Okazaki fragments to completer the strand

Question 19

Replication: Termination

Answer 19

-two new DNA molecules separate from each other, replication fork dismantled

Question 20

Helicase

Answer 20

Helps unwind the parent DNA
HELI = helix
CASE = break apart

Question 21

Primase

Answer 21

Synthesizes RNA primer used to generate Okazaki fragments

Question 22

Single strand-binding proteins

Answer 22

Help stabilize single stranded regions of DNA when it unwinds

Question 23

Topoisomerase ll

Answer 23

Helps to relieve the strain on the structure of the parent DNA that is generated from the unwinding of the double-helix (in prokaryotes)

Question 24

DNA polymerase l

Answer 24

• Removes RNA primer and fills gaps between Okazaki fragments
• recognizes and corrects errors in newly synthesized strands of DNA

Question 25

DNA polymerase ll

Answer 25

Proofreads newly synthesized DNA

Question 26

DNA polymerase lll

Answer 26

Catalyzes the addition of new nucleotides to the 3’ end of a growing nucleotide strand

Question 27

DNA Ligase

Answer 27

Joins the ends of Okazaki fragments in the lagging strand synthesis