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An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?
- a)Equal amount of light and heavy DNA
- b)Same density as that of parent DNA
- c)Lower density than parental types
- d)Intermediate density of each molecule of DNA
Correct answer is option 'C'. Can you explain this answer?
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An E. coli having a heavy DNA molecule labelled with 15N is allowed t...
Explanation:
When an E. coli having a heavy DNA molecule labeled with 15N is allowed to grow in a medium with normal 14NH4CI, the following can be observed:
- The newly synthesized DNA molecules will have a mixture of heavy (15N) and light (14N) nitrogen.
- As the cells divide and DNA replicates, the proportion of heavy nitrogen in the DNA will decrease.
- After 40 minutes, some of the cells will have completed one round of DNA replication, while others will still be in the process.
Based on this, the correct answer is option 'C': Lower density than parental types.
Here's why:
- DNA density can be measured using a technique called density gradient centrifugation, where DNA samples are spun in a tube containing a gradient of a heavy substance like cesium chloride (CsCl).
- The CsCl forms a gradient based on density, with the heaviest molecules settling at the bottom and the lightest at the top.
- When the DNA extracted from the culture after 40 minutes is subjected to density gradient centrifugation, the following can be observed:
- The parental DNA (heavy DNA with only 15N) will form a single band at the bottom of the gradient, with a high density.
- The newly synthesized DNA molecules will have a mixture of heavy and light nitrogen, and hence a lower density than the parental DNA.
- Since some cells will have completed one round of DNA replication, their DNA will have a higher proportion of light nitrogen and hence a lower density than the parental DNA.
- However, some cells will still be in the process of replicating their DNA, and their DNA will have a mixture of heavy and light nitrogen, resulting in an intermediate density between the parental and newly synthesized DNA.
- Overall, the DNA extracted from the culture after 40 minutes will appear as a smear on the gradient, with the majority of the DNA having a lower density than the parental DNA.
When an E. coli having a heavy DNA molecule labeled with 15N is allowed to grow in a medium with normal 14NH4CI, the following can be observed:
- The newly synthesized DNA molecules will have a mixture of heavy (15N) and light (14N) nitrogen.
- As the cells divide and DNA replicates, the proportion of heavy nitrogen in the DNA will decrease.
- After 40 minutes, some of the cells will have completed one round of DNA replication, while others will still be in the process.
Based on this, the correct answer is option 'C': Lower density than parental types.
Here's why:
- DNA density can be measured using a technique called density gradient centrifugation, where DNA samples are spun in a tube containing a gradient of a heavy substance like cesium chloride (CsCl).
- The CsCl forms a gradient based on density, with the heaviest molecules settling at the bottom and the lightest at the top.
- When the DNA extracted from the culture after 40 minutes is subjected to density gradient centrifugation, the following can be observed:
- The parental DNA (heavy DNA with only 15N) will form a single band at the bottom of the gradient, with a high density.
- The newly synthesized DNA molecules will have a mixture of heavy and light nitrogen, and hence a lower density than the parental DNA.
- Since some cells will have completed one round of DNA replication, their DNA will have a higher proportion of light nitrogen and hence a lower density than the parental DNA.
- However, some cells will still be in the process of replicating their DNA, and their DNA will have a mixture of heavy and light nitrogen, resulting in an intermediate density between the parental and newly synthesized DNA.
- Overall, the DNA extracted from the culture after 40 minutes will appear as a smear on the gradient, with the majority of the DNA having a lower density than the parental DNA.
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An E. coli having a heavy DNA molecule labelled with 15N is allowed t...
After 40 minutes, there will be two hybrid DNA and two light DNA. Therefore, overall density of DNA becomes less than that of parent DNA.
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An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer?
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An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer?.
An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer? for NEET 2024 is part of NEET preparation. The Question and answers have been prepared according to the NEET exam syllabus. Information about An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer? covers all topics & solutions for NEET 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for An E. coli having a heavy DNA molecule labelled with 15N is allowed to grow in a medium with normal 14NH4CI. Which of the following is correct for DNA molecules that were extracted from the culture after 40 minutes?a)Equal amount of light and heavy DNAb)Same density as that of parent DNAc)Lower density than parental typesd)Intermediate density of each molecule of DNACorrect answer is option 'C'. Can you explain this answer?.
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