Need help with a couple pf VCAA questions on the concept of one gene producing many proteins:
2015 Q7c
In the rat pituitary gland, GC stimulates the production of the growth hormone protein. However, in the rat liver, GC stimulates the production of the enzyme tryptophan oxygenase. Given that the genetic sequence is identical in all somatic rat cells, explain how the production of distinct proteins in different cell types could occur. (2 marks)
Answer: Factors expressed by regulator genes could lead to production of the different proteins.
Students were required to relate their answer to how the same genetic sequence could produce different proteins.
I understand VCAA's solution, however, would I still get the marks for other explanations?
- Different receptors/second messengers between the cells leading to different genes being activated
- Alternative splicing in RNA processing e.g. exon shuffling/intron retention
2017 Q1c
Different cells within an organism have different proteins. In some cases different proteins can be coded for by the same gene. Explain how the expression of a single gene can lead to the production of different proteins. (3 marks)
Answer:
• different post-transcriptional modification or modifications of the pre-mRNA
• different exons are joined or alternative splicing
• different nucleotide sequences/mRNA sequences, code for a different protein
• post-translational changes to the protein; for example, alternative folding
I'm unsure how much detail would be required here for the 3 marks, would I have to mention 3 different reasons, or just thoroughly explain one?
Cheers