4: DNA/RNA structure

Question 1

What is the central dogma of molecular biology?

Answer 1

The fact that all life is underpinned by proteins (hormones, enzymes, etc.). Link to DNA replication, transcription & translation (protein synthesis)

Question 2

What is the difference between RNA and DNA molecules?

Answer 2

RNA is made up of ribonucleotide monomer
RNA contains uracil NOT thymine
Most cellular RNAs are single stranded (allows it to fold into 3 dimensional structures that carry out structural, catalytic and regulatory roles in cells)

Question 3

Explain the different types of RNA and their functional roles in translation

Answer 3

• mRNA: (messenger RNA) codes for proteins. Information carrier; directs protein synthesis. Varies in size and is synthesised and rapidly degraded
• rRNA: (ribosomal RNA) component of ribosomes catalysing protein synthesis
• tRNA: (transfer RNA) decodes mRNA for protein synthesis, brings correct amino acid to end of polypeptide chain. Contains anticodon loop at the end.

Question 4

What are the types of regulatory RNAs, involved in the regulation of gene expression?

Answer 4

miRNAs (microRNA) = down regulate gene expression
siRNAs (small interfering RNA) = turn off gene expression

Question 5

Define the primary structure of an RNA molecule

Answer 5

The sequence of nitrogenous base pairs that constitute the RNA molecule

Question 6

Describe and explain the secondary structure of RNA

Answer 6

Hairpins and stem-loops
- formed by base pairing
- can be quote stable
- short hairpins with few nucleotides (5-10)
- stem loops may be 100s or 1000s of nucleotides long
- double stranded

Question 7

Explain the tertiary and quaternary structures of RNA

Answer 7

Tertiary = Pseudoknot = repeats of secondary structures (hairpins and stem loops)