Question

Genomic mammalian DNA cannot be expressed directly using bacterial expression vectors because mammalian genomic DNA contains introns, which the bacterial cell cannot excise. Complementary DNA, or cDNA, enables scientists to express mammalian DNA from a bacterial plasmid. Place the sentences into the correct order to describe the formation of double‑stranded cDNA. You will only use five of the seven sentences.

Answer 1

Answer:

1. DNA to be cloned
2. mature mammalian mRNA is isolated
3. reverse transcriptase, provided with a primer, synthesizes a strand of cDNA without introns
4. the mRNA is hydrolyzed by raising the pH
5. a primer site is created on the ssDNA
6. a complementary DNA strand is synthesized, forming a ds cDNA molecule.
7. dsDNA

Explanation:

cDNA is the acronym for complementary DNA. This DNA is a single or double stranded moolecule that is synthesized from a messenger RNA molecule. This molecule is used in studies that aim to clone eukaryotic genes in prokaryotic individuals. The result of this is the expression of a protein from a eukaryotic individual in prokaryotic individuals.

To form a double-stranded cDNA molecule, the following steps would be required:

1. DNA to be cloned
2. mature mammalian mRNA is isolated
3. reverse transcriptase, provided with a primer, synthesizes a strand of cDNA without introns
4. the mRNA is hydrolyzed by raising the pH
5. a primer site is created on the ssDNA
6. a complementary DNA strand is synthesized, forming a ds cDNA molecule.
7. dsDNA