Question

The cutting of DNA at specific locations became possible with the discovery of:

• A. Probes
• B. Restriction enzymes
• C. Selectable markers
• D. Ligases

Answer 1

The correct option is B

Restriction enzymes

The correct option is B.
Explanation of the correct option:

Option B:

1. A restriction enzyme is a bacterial protein that cleaves DNA sequences at sequence-specific places, resulting in DNA fragments having a known sequence at each end.
2. Certain laboratory processes, such as recombinant DNA technology and genetic engineering, require the use of restriction enzymes.
3. At the precise restriction site, restriction enzymes sever DNA links between the 3′ OH of one nucleotide and the 5′ phosphates of the next.
4. Adding methyl groups to certain bases at bacterial DNA recognition sites prevents the restriction enzyme from binding and so protects the bacterial DNA from being cut.
5. These are commonly referred to as molecular scissors.
6. Hind II was the first restriction enzyme to be identified.
7. These enzymes are commonly employed in DNA cloning investigations.

Explanation of the incorrect options:
Option A:

1. A probe is a single-stranded DNA or RNA sequence that is used to look for its complementary sequence in a sample genome.
2. When the probe comes into touch with the sample, the probe sequence hybridizes with its complementary sequence.
3. Chemical probes can aid in the identification of the link between a molecular target and the larger biological effects of modifying that target in cells or organisms.
4. They are also extremely synergistic with biological or genetic methods for studying protein activities.

Option C:

1. A selectable marker is a gene that, when introduced into a cell, particularly a bacterium or cells in culture, provides a phenotype amenable to artificial selection.
2. Selectable markers are used to select successful transformants from untransformed cells, and they give cells with exogenous DNA a survival advantage.
3. Transformants are cells that have received additional genetic material, either experimentally or by infection; they might refer to a cancerous cell.
4. Bacterial cells that take up the plasmid but do not incorporate the plasmid DNA into their genome are non-transformants.
5. There are two sorts of transformants: recombinants and non-recombinants.

Option D:

1. Ligase is an enzyme that helps two molecules link together.
2. A DNA ligase, for example, forms a phosphodiester connection between two pieces of DNA.
3. By connecting breaks in the phosphodiester backbone of DNA that occur during replication and recombination, as well as as a result of DNA damage and repair, DNA ligases serve an important role in maintaining genomic integrity.
4. LIG1, LIG3, and LIG4 are human genes that encode ATP-dependent DNA ligases.

Final answer: The cutting of DNA at specific locations became possible with the discovery of restriction enzymes.