Nucleic Acids

Question 1

What are the two types of nucleic acid

Answer 1

DNA (deoxyribonucleic acid)
RNA (ribonucleic acid)

Question 2

What are the monomers and polymers for nucleic acids

Answer 2

Nucleotides and polynucleotides

Question 3

What are the components of a nucleotide? Can you draw them?

Answer 3

Phosphate, pentose sugar, nitrogenous base

Question 4

Pyramidines

Answer 4

Double ringed
Larger
Pyramidine, cytosine, uracil (RNA) and thymine (DNA)
Pyramids are sharp so they CUT

Question 5

Purines

Answer 5

Single ringed
Smaller
Purine, adenine and guanine

Question 6

What reactions form polynucleotide chains

Answer 6

Condensation reactions

Question 7

Phosphate-sugar bonds are called

Answer 7

Ester bonds.
Become phosphodiester bonds between bases (C3 on sugar, C5 on phosphate)

Question 8

Sugar-base bond

Answer 8

Glycosidic bond

Question 9

Chargraff’s rules

Answer 9

There are equal adenine and thymine, and equal cytosine and guanine

Question 10

mRNA

Answer 10

Messenger RNA
Brings information from DNA in nucleus to ribosomes in cytoplasm, directs synthesis of polypeptides
Made in nucleus, moves to cytoplasm
What does it look like?

Question 11

tRNA

Answer 11

transport RNA
Transports amino acids to ribosomes, positions each amino acid at correct place on polypeptide chain
In cytoplasm
What does it look like?

Question 12

rRNA

Answer 12

ribosomal RNA
Site of polypeptide synthesis, not involved in coding
Ribosomes
What does it look like?

Question 13

DvsRNA - how many strands?

Answer 13

2 1

Question 14

DvsRNA - name of pentose sugar?

Answer 14

Deoxyribose, ribose

Question 15

DvsRNA - names of nitrogenous bases?

Answer 15

Adenine, guanine, cytosine

Thymine
Uracil

Question 16

DvsRNA - number of different types?

Answer 16

1 3

Question 17

DvsRNA - location in cell?

Answer 17

Nucleus
Nucleus, cytoplasm, ribosomes

Question 18

DvsRNA - relative length?

Answer 18

Long, short

Question 19

DvsRNA - lifespan?

Answer 19

Long, short

Question 20

DvsRNA - function?

Answer 20

Contain genetic coding
Transcribe and translate DNA

Question 21

Four requirements for semi-conservative replication

Answer 21

• The four types of nucleotide (each with their bases of adenine, guanine, cytosine or thymine) must be present
• Both strands of DNA acts as a template
• The enzymes DNA polymerase and DNA helicase must be present
• A source of energy is required to drive the process

Question 22

Semi conservative replication

Answer 22

Watson and Crick 1953
2 original polynucleotide strands of the DNA molecule separate
Each is a template on which a new complementary strand is laid down
Semi conservative=one chain of the original molecule is retained, one is newly synthesised
Requires energy, and the enzymes DNA Polymerase and Helicase

Question 23

Semi conservative replication process

Answer 23

DNA helicase breaks H bonds between bases, so helix unwinds, forming 2 single strands. Each is a template.
Complementary base pairing = free floating DNA nucleotides are attracted to complementary exposed bases
Condensation reactions join nucleotides (catalysed by DNA Polymerase), forming H bonds between bases

Question 24

DNA Polymerase process

Answer 24

Only complementary to the 3’ end of hte newly forming DNA strand, so can only add nucleotides to the new strand at the 3’ end.
The enzyme can only add nucleotides to the new strand at the 3’ end, so new strand is made in 3-5 direction.
Because both strands are antiparallel, DNA Polymerase works in different directions on each strand

Question 25

Evidence for semi conservative replication - meselson-stahl

Answer 25

Grew e-coli in heavy nitrogen (extra neutron) Those strands which contained heavy N would go to the bottom of the centrifuge. Switched to light nitrogen, let them duplicate. Over generations, (look up results), half of the heavy DNA was replaced by light DNA