Question

When using bacteria to clone a human gene and express its product-as in the case of insulin-the gene cannot contain introns because bacteria do not have the enzymes to process mRNA. Therefore:

Options

• if the sequence is known, very small human genes can be built with a DNA synthesizer in a laboratory and they will lack introns

• reverse transcriptase can be used to make DNA 'backwards' from human mature mRNA and this would lack introns

• it is impossible to use bacteria to express human gene products because all human genes have introns

• both (a) and (b) are true

Answer 1

both (a) and (b) are true

Explanation:

When cloning a human gene in bacteria, the gene must lack introns because bacteria do not have the enzymes to remove introns during mRNA processing. Therefore, if the DNA sequence is known, small human genes without introns can be synthesized artificially in the laboratory. Alternatively, reverse transcriptase can be used to make complementary DNA (cDNA) from mature human mRNA, which naturally lacks introns. Both methods produce intron-free DNA suitable for expression in bacteria, such as for producing human insulin.