1. Explain the difference between a genome and a proteome.
Answer
A genome is all the organism's genes. A proteome is all the proteins that a cell produces using the DNA.
2. The sections between the exons are all removed from pre-mRNA. Name these sections.
Answer
These sections are called introns.
3. RNA polymerase is an enzyme that is involved in the process of transcription. Describe the role RNA polymerase plays in this process.
Answer
It joins adjacent RNA nucleotides together by catalysing the formation of a phosphodiester bond.
4. Translation is the process by which a polypeptide chain is synthesised. Describe the role played by tRNA in this process.
Answer
tRNA has an anticodon that is complementary to the codon on mRNA. It carries a specific amino acid that corresponds to the codon–anticodon pairing. The tRNA transports this amino acid to the ribosome, where it can form peptide bonds with adjacent amino acids during the process of translation.
5. Scientists have found that the same gene can produce more than one protein. They think this happens because of "alternative splicing". This is shown in the figure below. Name process X.
Answer
The process X is called translation.
6. Use the figure above to explain how this gene is able to produce three different proteins, A, B and C.
Answer
Exons are in a different order, which means the base sequence is different. This results in different amino acids being coded for in a different sequence.
7. Proteins A, B and C have different tertiary structures. Explain why.
Answer
Proteins A, B, and C have different tertiary structures because different ionic, hydrogen, and disulfide bonds form in different places. This occurs since different R groups are adjacent in different sequences, causing bonds to form in different positions.
8. When scientists first decoded the human genome, they estimated that humans had between 20000–25000 genes. The number of proteins a human is able to make is far greater than this number. Explain how alternative splicing causes this to happen.
Answer
One gene can code for more than one polypeptide chain.
9. Aminoacyl-tRNA synthetase (aaRS) is an enzyme involved in the attachment of the correct amino acid to its corresponding tRNA. This process is referred to as "loading" the tRNA. Once it is loaded, the tRNA molecule can be involved in the process of translation by delivering the amino acid to the growing polypeptide chain. The antibiotic mupirocin works by inhibiting aaRS in bacteria. Explain how mupirocin kills bacteria.
Answer
If enzyme is inhibited then tRNA can't load the corresponding amino acid. Therefore the production of the polypeptide chain will be stopped and amino acids will not be delivered to ribosome. Bacteria won't be able to grow or divide without their necessary proteins being made.
10. There are growing concerns for bacteria developing resistance to the antibiotic, and so scientists are trying to develop new drugs that act in the same way as mupirocin. One challenge they have faced in early testing is that the synthetic versions of this antibiotic also inhibit human aaRS. Suggest why this might occur.
Answer
Both bacteria and humans need the enzyme to load tRNA.