21: W1 RNA, protein synthesis, molecular control of the genome and gene editing

Question 1

What are the three major molecular players of the cell?

Answer 1

• DNA
• Proteins
• RNA

Question 2

Describe the RNA world hypothesis

Answer 2

• The idea that RNA was the original biomolecule
• Spontaneously arose due to the presence of the correct precursors and environmental conditions
• Early RNA molecules may have had enzymatic (functional) activity
• Required a replicase (biomolecule capable of replicating other RNA molecules)
• Requires biomolecules functionally capable of performing the role of the modern ribosome
• Also requires an RNA ‘protoribosome’, a RNA molecule or collection of RNA molecules capable of performing the role of the modern ribosome
• This is an attractive concept although it has not been proven

Question 3

What did Thomas Cech discover in the 1970s?

Answer 3

• He found that RNA could function as an enzyme
• During the process he also discovered that eukaryotic mRNA contained introns which meant that the pre-mRNA had to be processed to removed the introns resulting in mature mRNA
• This experiment revealed that RNA itself could have catalytic activity as an intron was removed when there was no protein present
• These RNA enzymes have been given the name ribozyme

Question 4

What is a ribozyme?

Answer 4

An RNA molecule capable of acting as an enzyme

Question 5

What were the three original RNAs?

Answer 5

• rRNA
• mRNA
• tRNA

Question 6

What are ncRNA?

Answer 6

non-coding RNA

• These ncRNAs play a major role in controlling every aspect of our RNA genome’s operation, and controlling multicellular development and homeostasis
• Originally thought to be relatively non-functioning, but now it has been shown that they actually do have key functions

Question 7

What are miRNA?

Answer 7

microRNAs

• The first well-defined group of ncRNAs
• Begin as a long ncRNA (200+ bases) transcribed from the genome
• Processed in the nucleus into a small intermediate pre-miRNA (approximately 65 bases)
• Transported to the cytoplasm and further processed into miRNA (21-25 bases)

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Question 8

Describe a practical implication of miRNA

Answer 8

In the development of the human heart the miR-1 is critical for regulating the protein levels of Hand2 protein in order to get correct development of the heart.

This miRNA affects the level of Hand2 protein by repressing the translation of its mRNA