Main steps in the formation of Recombinant DNA are given below. Arrange these steps in a correct sequence.
A. Insertion of recombinant DNA into the host cell.
B. Cutting of DNA at specific location by restriction enzyme.
C. Isolation of desired DNA fragment.
D.Amplification of gene of interest using PCR
Choose the correct answer from the option given below:
Which one of the following statement is not true regarding gel electrophoresis technique?
Explanation:
Option 3 is not true. In gel electrophoresis, DNA is visualized using dyes such as ethidium bromide, which after UV illumination shows bright orange fluorescence. A chromogenic substrate does not produce blue DNA bands in this technique. The statements 1, 2, and 4 are correct: elution refers to extracting DNA strands from the gel, DNA fragments are stained with ethidium bromide, and under UV light, ethidium bromide–stained DNA bands appear orange.
🧠 Did You Know?
Ethidium bromide is a common DNA stain used in gel electrophoresis because it binds DNA and fluoresces under UV light, making the fragments visible.
💡 NCERT Memory Line:
Gel electrophoresis visualization relies on ethidium bromide staining and UV light to see orange fluorescent DNA bands; chromogenic blue bands are not part of this method.
Given below are two statements : one is labelled as
Assertion (A) and the other is labelled as Reason (R). Assertion (A): Polymerase chain reaction is used in DNA amplification. Reason (R): The ampicillin resistant gene is used as a selectable marker to check transformation
In the light of the above statements, choose the correct answer from the options given below :
Given below are two statements: Statement I: Restriction endonucleases recognise specific sequence to cut DNA known as palindromic nucleotide sequence. Statement II: Restriction endonucleases cut the DNA strand a little away from the centre of the palindromic site.
In the light of the above statements, choose the
most appropriate answer from the options given
below:
Explanation:
Statement I is correct: Restriction endonucleases recognize specific palindromic nucleotide sequences. Statement II is also correct: these enzymes cut the DNA within the recognition site, often a little away from the center of the palindromic sequence, producing "sticky" or blunt ends as described in NCERT. Thus, both statements are correct.
🧠 Did You Know?
Most Type II restriction enzymes cut within or near the palindromic target, enabling precise genetic manipulation for cloning experiments.
💡 NCERT Memory Line:
Restriction endonucleases recognize palindromic sequences and cut within those sites, often not exactly at the center.
