DNA and RNA

Question 1

Nucleotide structure

Answer 1

Made up of a phosphate group, a pentose sugar and an organic base
Bases:
A = Adenine
T = Thymine (only in DNA)
C = Cytosine
G = Guanine
U = Uracil (only in RNA, replaces T)
- A pairs with T or U - forms a double bond
- C pairs with G - forms a triple bond
- Bonds between nucleotides are phosphodiester bond

Question 2

DNA

Answer 2

Deoxyribonucleic acid
- A, T, C and G
- Deoxyribose sugar
- Double stranded helix

Question 3

RNA

Answer 3

Ribonucleic acid
- A, U, C and G
- Ribose sugar
- 3 types of RNA:
- mRNA = codes for amino acid sequence
- rRNA = translates the RNA
- tRNA = brings amino acids to ribosomes
- Shorter single stranded helix
- Ribosomes are made up of RNA and proteins

Question 4

DNA replication

Answer 4

1) DNA helicase breaks the hydrogen bonds between 2 strands of DNA - unwinding the double helix and providing 2 single strands
2) In these single strands, free nucleotides bind to their complementary bases
3) DNA polymerase (enzyme) joins the new nucleotides together, creating the phosphodiester bonds
4) 2 identical strands of DNA are formed
This is semi-conservative replication