Question

In genetic engineering, antibiotics are used?

• A. As selectable markers
• B. As sequence from where replication starts
• C. To keep cultures free of infection
• D. To select healthy vectors

Answer 1

The correct option is A

As selectable markers

The correct answer is option A.

Explanation of the correct answer.

1. The recombinant cells are distinguished from non-recombinant ones using a gene that makes them resistant to antibiotics, which are carried by vectors.
2. Only recombinant cells would have this gene and would be able to live in an antibiotic-rich environment.
3. Selectable markers are those genes that distinguish recombinant cells from non-recombinant ones and that the host cell needs for growth in particular conditions.
4. Example: Beta-lactamase that makes bacterial hosts resistant to ampicillin.

Explanation of incorrect answers:

Option B:

1. The easiest strand to reproduce is the leading one. A little piece of RNA known as a primer then attaches to the 3' end of the DNA strand after the DNA strands have been split. Replication always begins with primer binding.
2. DNA double helix unwinding occurs at Ori sites. It is a genomic sequence that serves as the starting point or origin of DNA replication. Any DNA fragment can begin to replicate when it is linked to the ori region.
3. The production of a primer, a brief section of RNA that serves as the beginning point for the synthesis of fresh DNA, follows. The DNA is then replicated by a protein called DNA polymerase by matching bases to the original strand.

Option C:

1. While preparing the culture, there is a chance for the spreading of affecting of infection
2. To prevent the infection while preparing the culture, they will add another substance that will not infect the culture medium.

Option D:

1. A vector is a DNA molecule (typically a plasmid or a virus) used in molecular biology to transport a specific DNA segment into a host cell as part of a cloning or recombinant DNA process.
2. Features of a good vector: self-replicating, possess a restriction site for Restriction Endonuclease enzymes, must possess some marker gene, and have multiple cloning sites

Final answer: In genetic engineering, antibiotics are used as selectable markers.