What is the criterion for DNA fragments movement on agarose gel during gel electrophoresis?

  • The larger the fragment size, the farther it moves

  • The smaller the fragment size, the farther it moves

  • Positively charged fragments move to farther end

  • Positively charged fragments move to farther end


B.

The smaller the fragment size, the farther it moves

During gel electrophoresis, DNA fragments separate (resolve) according to their size through sieving effect provided by agarose gel.

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Restriction endonuclease

  • cuts the DNA molecule randomly

  • cuts the DNA molecule at specific sites

  • restricts the synthesis of DNA inside the nucleus

  • restricts the synthesis of DNA inside the nucleus


B.

cuts the DNA molecule at specific sites

Restriction endonuclease is a type of enzyme that can cleave molecules of DNA at a particular site called Restriction site having polindromic sequence. These enzymes are produced by many bacteria and protect the cell make leaving and destroying the DNA of invading viruses.  Now a days, restriction enzymes are widely used in the techniques of genetic engineering.
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A gene whose expression helps to identify transformed cell is known as

  • Selectable marker

  • Vector

  • Plasmid

  • Plasmid


A.

Selectable marker

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Lysozyme that is present in perspiration, saliva and tears, destroys

  • certain fungi

  • certain types of bacteria

  • all viruses

  • all viruses


B.

certain types of bacteria

Lysozyme is an enzyme that breaks down bacterial cell walls and provides protection against bacterial invasion in the skin, mucous membranes and many body fluids. It is found in tears, sweat and saliva.

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During DNA replication, Okazaki fragments are used to elongate

  • The leading strand towards replication fork

  • The lagging strand towards replication fork

  • The leading strand away from replication fork

  • The leading strand away from replication fork


D.

The leading strand away from replication fork

Two DNA polymerase molecules work simultaneous at the DNA fork, one on the leading strand and the other on the lagging strand.
Each Okazaki fragment is synthesized by DNA polymerase at lagging strand in 5  3 direction.
New Okazaki fragments appear as the replication fork opens further.
As the first Okazaki fragment appears away from the replication fork, the direction of elongation would be away from replication fork.

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