Ch2 Nucleic acids

Question 1

Nucleotide structure

Answer 1

1. pentose sugar
2. phosphate sugar
3. nitrogenous base

Question 2

Polynucleotides

Answer 2

1. Joined by phosphodiester bonds
2. condensation reaction between pentose sugar and phosphate

Question 3

Structure of DNA

Answer 3

1. two polynucleotide stands
2. double helix
3. deoxyribose sugar and phosphate backbone
4. adenine, thymine, guanine and cytosine
5. specific base pairing A+T / C+G
6. hydrogen bonding

Question 4

Meselson and Stahl experiment

Answer 4

1. bacteria grown in 14N and other in 15N
2. DNA sample taken and centrifuged
3. 15N settled lower than 14N(heavier mass)
4. bacteria from 15N put with other
5. left for one round DNA replication
6. DNA sample taken and centrifuged
7. in caesium chloride solution
8. settled in middle
9. contained strand 14N and one 15N

Question 5

Structure of RNA

Answer 5

1. short
2. ribose sugar
3. adenine, uracil, guanine and cytosine
4. single stranded

Question 6

6. DNA adaptations

Answer 6

1. very stable
2. hydrogen bonds between polynucleotides- separation for replication and transcription
3. very large-carry lots of genetic information
4. strong phosphodiester backbone- protects H bonds and bases
5. complementary base pairing -DNA to replicate and be transcribed
6. coiling gives compact shape

Question 7

Semi-conservative replication

Answer 7

1. DNA helicase breaks H bonds
2. double helix unravels into 2 separate strands
3. strands act as template
4. free nucleotides bond to complementary base pairs
5. DNA polymerase bonds phosphodiester backbone
6. contains one parent strand and one new strand

Question 8

Stability of DNA

Answer 8

1. phosphodiester backbone protects reactive bases inside helix
2. many hydrogen bonds
3. prevents code being corrupted

Question 9

Replication discovery

Answer 9

Watson and Crick