Question

a)  You cut a gene out of the DNA of a eukaryotic cell and insert it into the DNA of a bacterial cell. You find that the bacteria do not produce the protein you wanted but instead, a much larger disorganized protein is produced. Explain what happened.

b) Your teammate claims to have found a mutation in the serine tRNA synthetase that causes serine amino acids to be linked to a tRNA with a UAA anti-codon. Is this possible? If so, then what would the consequence be for the cell?

Answer 1

a. Eukaryotes contain split genes. i.e. their gene coding sequences are interrupted by intervening non-coding sequences.
Coding sequences = Exons
Non-coding sequences = Introns
These introns are removed during splicing to produce the mature mRNA.

However, prokaryotes do not contain introns or splicing machinery. So, they cannot express a eukaryotic gene with introns.

2. Yes
It is possible.
The tRNA synthetase enzyme ligates an amino acid to its cognate tRNA. Mutations in tRNA synthetase can alter its specificity.
Anticodon = 5'-UAA-3'
Codon = 5'-UUA-3'
= Leu
Due to this mutation, Ser is incorporated at the place of Leu in the polypeptide.