E. coli fully labelled with N 15 is allowed to grow in N 14 medium. The two strands of DNA molecule of the first generation bacteria have:

Different density but do not resemble with their parent DNA

Same density resemble with their parent DNA

Same density but do not resemble with their parent DNA

Different density but resemble with their parent DNA

HARD

Earn 100

An E. coli whose DNA is fully labeled by $^{15} N$ is grown in a medium containing $^{14} {NH}_{4} Cl$ . What will be the percentage of hybrid $(^{15} N /^{14} N)$ and light $(^{14} N /^{14} N)$ DNA molecules at the end of $80$ minutes (assume that doubling time of E. coli is $20$ minutes)?

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Important Questions on Molecular Basis of Inheritance

HARD

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

"Use of heavy isotope of nitrogen by Meselson and Stahl demonstrated semi-conservative mode of replication of a DNA molecule." Explain how did they arrive at this conclusion.

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

E. coli fully labelled with

{}^{15}N

is allowed to grow in

{}^{14}N

medium. The two strands of DNA molecule of the first generation bacteria have:

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Matthew Meselson and Franklin Stahl grew E.coli (doubling time is

20 \min

) in medium containing

{}^{15}{NH}_{4} Cl

for many generations. Then the E. coli was transferred to medium containing

{}^{14}{NH}_{4} Cl

. After

40

minutes, the cells were harvested and

DNA

was extracted and subjected to caesium chloride density gradient centrifugation. The proportion of light and hybrid

DNA

densities will be:

HARD

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Give an account of Meselson and Stahl's experiment.

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

E. coli has only

4.6 \times 10^{6}

base pairs and completes the process of replication within

18

minutes; then the average rate of polymerisation is approximately:

HARD

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

What is the significance of Meselson and Stahl's experiment?

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Arrange the following events of the replication of DNA. Choose the correct alternative?
(i) Bonds between complementary bases breaks.
(ii) Bonds between complementary bases forms.
(iii) DNA molecules are uncoiled.
(iv) Opposite strands separate.
(v) Sugar phosphate bonds form.
(vi) Free nucleotides align with the complementary nucleotides on each strand.

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

What is the function of DNA ligase?

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Light DNA

(N^{14})

transferred to

(N^{15})

labelled culture medium for replication. The ratio of total number of

N^{15}

and

N^{14}

labelled strands of DNA extracted from the culture after three generations

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Which one of the following elements is not directly involved in transcription?

HARD

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Describe the semiconservative method of DNA replication with diagram.

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

During DNA replication, Okazaki fragments are used to elongate:

HARD

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Diagrammatically express the Watson Crick's semiconservative models of DNA replication.

HARD

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Meselson and Stahl carried out centrifugation in CsCl₂ density gradient to separate:

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

What are Okazaki fragments?

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Describe the mechanism of DNA replication with a suitable diagram.

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Draw a labelled diagram of replicating fork in DNA helix.

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Which one of the following will be the ratio of heavy, intermediate and light bands in Meselson and Stahl's experiment after two generations if

DNA

replication were conservative?

MEDIUM

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

Choose the correct pair from the following.

EASY

Biology>Genetics and Evolution>Molecular Basis of Inheritance>Structure, Replication and Packaging of DNA

A mixture of equal numbers of fast and slow dividing cells is cultured in medium containing a trace amount of radioactively labeled thymidine for one hour. The cells are then transferred to regular (unlabeled) medium. After 24hrs of growth in regular media

An E. coli whose DNA is fully labeled by 15N is grown in a medium containing 14NH4Cl. What will be the percentage of hybrid 15N/14N and light14N/14N DNA molecules at the end of 80 minutes (assume that doubling time of E. coli is 20 minutes)?

Important Questions on Molecular Basis of Inheritance

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An E. coli whose DNA is fully labeled by $^{15} N$ is grown in a medium containing $^{14} {NH}_{4} Cl$ . What will be the percentage of hybrid $(^{15} N /^{14} N)$ and light $(^{14} N /^{14} N)$ DNA molecules at the end of $80$ minutes (assume that doubling time of E. coli is $20$ minutes)?