2B: Nucleic Acids

Question 1

What are nucleic acids made from?

Answer 1

Nucleotides

Question 2

Features of DNA

Answer 2

• Has A, T, C, G
• Has deoxyribose sugar
• Double stranded
• Strands run antiparallel
• Twists around a full rotation every 10.5 bases

Question 3

Features of RNA

Answer 3

• Uses A, U, C, G
• Single stranded
• Has ribose sugar

Question 4

Structure of a nucleotide

Answer 4

1. Nitrogenous base
2. Pentose sugar
3. Phosphate group(s)

Question 5

What joins the sugar-phosphate backbone in DNA/RNA?

Answer 5

phosphodiester bonds

Question 6

What joins the two strands in DNA?

Answer 6

Hydrogen bonds between complimentary bases

Question 7

Steps in RNA Polymerization

Answer 7

1. Helicase unwinds DNA
2. RNA assembles at the Promoter and moves along the Template strand from 3’ - 5’
3. Using free floating RNA nucleotides, RNA Polymerase synthesizes a pre-mRNA chain that is identical to the coding strand, apart from having Uracil instead of Thymine
4. RNA Polymerase stops transcribing and detaches from the DNA once it reaches the termination sequence
5. The DNA is rewinded while the pre-mRNA is detached

Question 8

Steps in DNA Polymerization

Answer 8

1. DNA unwinded by helicase
2. DNA Polymerase synthesizes a new strand in a 5’ - 3’ direction, while reading 3’ -5’. Ligase later joins the sugar-phosphate backbones of the new strands
3. The new DNA molecules rewind back into their original shape