RNA and DNA

Question 1

what makes up an RNA nucleotide?

Answer 1

• ribose sugar
• phosphate
• organic base (A,U,C or G)

Question 2

what makes up an DNA nucleotide?

Answer 2

• deoxyribose sugar
• phosphate
• organic base (A,T,C or G)

Question 3

Give 4 differences between RNA and DNA

Answer 3

• DNA is longer, RNA is shorter
• DNA is double-stranded, RNA is single-stranded
• DNA contains deoxyribose, RNA contains ribose
• (some) DNA contains Thymine as a base, RNA contains Uracil
• C.B.P is present in DNA, it is not present in RNA

Question 4

What is the role of DNA?

Answer 4

base sequence of genes codes for functional RNA and polypeptides

Question 5

What is mRNA?

Answer 5

a single-stranded polynucleotide with a complementary base sequence to 1 gene from DNA (no introns)

Question 6

What is rRNA?

Answer 6

a component that makes up ribosomes

Question 7

What is the role of tRNA?

Answer 7

transfer complementary amino acid to the site of protein synthesis

Question 8

how do polynucleotides form?

Answer 8

condensation reactions between nucleotides, forming phosphodiester bonds (sugar-phosphate backbone)

Question 9

How many bonds form between A and T?

Answer 9

2 hydrogen bonds

Question 10

How many bonds form between C and G?

Answer 10

3 hydrogen bonds

Question 11

How is DNAs structure related to its function?

Answer 11

• many H bonds & sugar-phosphate backbone gives stability
• helix is compact, so lots stored in small space
• double-stranded for semi-conservative replication
• H bonds are weak (on individual scale) so can be broken for replication
• complementary base pairing

Question 12

How does DNA replicate?

Answer 12

Semi-conservative replication

Question 13

What is meant by semi-conservative replication?

Answer 13

one of the ‘old’ DNA strands and one new DNA strand make up the new DNA molecule

Question 14

How is the structure of mRNA related to its function?

Answer 14

• breaks down quickly; so no excess polypeptide forms
• complementary codons so specific amino acids are coded for
• single stranded so ribosome can move along easily

Question 15

Outline the process of semi-conservative DNA replication

Answer 15

1) DNA helicase breaks H bonds
2) strands acts as template molecules
3) free nucleotides line up with exposed bases in complementary base pairing
4) DNA polymerase catalyses the reaction forming phosphodiester bonds between adjacent nucleotides on new strand
5) H bonds reform

Question 16

What is the general role of RNA?

Answer 16

transfer genetic information