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

In Meselson and Stahls experiment if E coli was allowed to grow for 80 minutes then what would be the proportion of light and intermediate density of DNA molecules respectively if E coli divides in every 20 minutes

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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?

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

Taylor conducted the experiments to prove the semiconservative mode of chromosome replication on:

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

Experiments involving use of radioactive thymidine to detect distribution of newly synthesized DNA in the chromosome was performed on which plant?

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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:

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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)?

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

Semiconservative replication of DNA was first demonstrated in

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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:

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

The experimental proof for semiconservative replication of DNA was first shown in a

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

"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.

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

Describe the semiconservative method of DNA replication with diagram.

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

Give an account of Meselson and Stahl's experiment.

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

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

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins which carry out the essential functions of life through systems of specialized cells.>Structure and Function - Systems of specialized cells within organisms help them perform the essential functions of life.All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins, which carry out most of the work of cells.

Choose the correct pair from the following.