Question

A classic experiment was conducted where DNA was made from nucleotides which only contained the heavy isotope of nitrogen, N^15. This N^15-labeled DNA was then placed in a medium containing nucleotides made of only the lighter isotope, N^14. In the presence of the necessary enzymes, after a period of time, the DNA doubled in number, and the DNA was a hybrid of N^15 and N^14 labeled nucleotides. After another brief period, the DNA doubled again, but 50% of the DNA was still a hybrid of N^15 and N^14 labeled nucleotides, while the other 50% of the DNA was uniformly composed of N^14-labeled nucleotides. These results are evidence of what important discovery about DNA? Choose all that apply. 1. DNA nucleotides can be made with either isotopes of nitrogen. 2. To replicate DNA, the parent DNA remains intact while serving as a model to synthesize new DNA. 3. To replicate DNA, the parent DNA strands split and each strand individually serves as a template to make a new complementary strand of DNA. 4. DNA replication is dispersive. 5. DNA replication is semi-conservative. There is a mutation in the gene that codes for the synthesis of DNA polymerase δ in the exonuclease domain of the protein for a plant cell. As a result, the enzyme does not contain its regular exonuclease function during DNA replication. If during DNA replication, there is an error in the pairing of nucleotides between parent and daughter DNA, which of the following could occur? Choose all that apply. 1. p53 protein would potentially find the error when proofreading DNA during the G1 phase. 2. Cyclin D-cdk complex would potentially find the error when proofreading DNA during the G1 phase. 3. Mismatch repair enzymes would locate, excise, and replace the single error or region of the error in the elongating daughter DNA strand only if the parent strand was methylated. 4. Nucleotide excision repair enzymes would remove the region of DNA with the error, identifiable by a kink or bend in the elongating strand, if the error were induced by UV radiation or chemical exposure. 5. The error in the DNA synthesized would go undetected if it is a nonsense mutation.

Name: a classic experiment was conducted where dna was made from nucleotides which only contained the heavy isotope of nitrogen n15 this n15 labeled dna was then placed in a medium containing nucl 38428
Uploaded: 2023-09-05T16:23:34-08:00
Duration: 8 min 36 s
Channel: Jenny Wu
Description: a classic experiment was conducted where dna was made from nucleotides which only contained the heavy isotope of nitrogen n15 this n15 labeled dna was then placed in a medium containing nucl 38428

These results are evidence of what important discovery about DNA? Choose all that apply.
1. DNA nucleotides can be made with either isotopes of nitrogen.
2. To replicate DNA, the parent DNA remains intact while serving as a model to synthesize new DNA.
3. To replicate DNA, the parent DNA strands split and each strand individually serves as a template to make a new complementary strand of DNA.
4. DNA replication is dispersive.
5. DNA replication is semi-conservative.

There is a mutation in the gene that codes for the synthesis of DNA polymerase δ in the exonuclease domain of the protein for a plant cell. As a result, the enzyme does not contain its regular exonuclease function during DNA replication. If during DNA replication, there is an error in the pairing of nucleotides between parent and daughter DNA, which of the following could occur? Choose all that apply.
1. p53 protein would potentially find the error when proofreading DNA during the G1 phase.
2. Cyclin D-cdk complex would potentially find the error when proofreading DNA during the G1 phase.
3. Mismatch repair enzymes would locate, excise, and replace the single error or region of the error in the elongating daughter DNA strand only if the parent strand was methylated.
4. Nucleotide excision repair enzymes would remove the region of DNA with the error, identifiable by a kink or bend in the elongating strand, if the error were induced by UV radiation or chemical exposure.
5. The error in the DNA synthesized would go undetected if it is a nonsense mutation.

Added by Ashley F.

Biology for AP Courses

Julianne Zedalis, John Eggebrecht

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Solved by Expert Jenny Wu

09/05/2023

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For the first question, the experiment showed that DNA replication is semi-conservative, meaning that each daughter DNA molecule contains one strand from the parent DNA molecule and one newly synthesized strand. Show more…

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A classic experiment was conducted where DNA was made from nucleotides which only contained the heavy isotope of nitrogen, N^15. This N^15-labeled DNA was then placed in a medium containing nucleotides made of only the lighter isotope, N^14. In the presence of the necessary enzymes, after a period of time, the DNA doubled in number, and the DNA was a hybrid of N^15 and N^14 labeled nucleotides. After another brief period, the DNA doubled again, but 50% of the DNA was still a hybrid of N^15 and N^14 labeled nucleotides, while the other 50% of the DNA was uniformly composed of N^14-labeled nucleotides. These results are evidence of what important discovery about DNA? Choose all that apply. 1. DNA nucleotides can be made with either isotopes of nitrogen. 2. To replicate DNA, the parent DNA remains intact while serving as a model to synthesize new DNA. 3. To replicate DNA, the parent DNA strands split and each strand individually serves as a template to make a new complementary strand of DNA. 4. DNA replication is dispersive. 5. DNA replication is semi-conservative. There is a mutation in the gene that codes for the synthesis of DNA polymerase δ in the exonuclease domain of the protein for a plant cell. As a result, the enzyme does not contain its regular exonuclease function during DNA replication. If during DNA replication, there is an error in the pairing of nucleotides between parent and daughter DNA, which of the following could occur? Choose all that apply. 1. p53 protein would potentially find the error when proofreading DNA during the G1 phase. 2. Cyclin D-cdk complex would potentially find the error when proofreading DNA during the G1 phase. 3. Mismatch repair enzymes would locate, excise, and replace the single error or region of the error in the elongating daughter DNA strand only if the parent strand was methylated. 4. Nucleotide excision repair enzymes would remove the region of DNA with the error, identifiable by a kink or bend in the elongating strand, if the error were induced by UV radiation or chemical exposure. 5. The error in the DNA synthesized would go undetected if it is a nonsense mutation.

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00:01 So what we have is a class experiment of method of the star that conducted with dna was made from nucleotide that contained heavy isotope of nitrogen n15.

00:12 This n15 label dna was then placed in a medium containing a nucleotide made of only the lighter isotope n14.

00:20 The presence of the necessary enzyme after the period of time, the dna doubled in number and the dna was a hybrid of n15 and 14.

00:28 Now after another brief period of dna double again, now this time 50 % of dna was a hybrid and the other 50 % was a uniformly 14 and 14 labeled nucleotide.

00:42 So these results are evidence of which of the following discovery of the protein, dna.

00:49 So choose all, apply.

00:52 So the very first thing we know that the dna can be made of either isotope of nitrogen.

00:59 So this is the first one you're going to choose because obviously dna can be labeled both n15 and 14 which means that they can use both n14 and n15.

01:19 So both of them can be made, can be used to make dna.

01:36 And what about the rest of other options? so let's take a look at the two rounds of dna replication.

01:42 So you start out with n15.

01:46 Which both dna strand will be 15.

01:48 Then it was moved to an n14 medium.

01:53 After first round obviously the two strands of dna will separate from each other because this is called a semi -conservative.

01:59 The two parental strand will split.

02:02 Then each will be used as a template to make new strand that is made of n14.

02:07 So this is why after first round of dna replication you'll have two double strand dna that both made of hybrid.

02:17 Now the second round again according to semi -conservative model the two strand of dna was split.

02:27 This is the top hybrid and then you have another hybrid.

02:31 Each will actually will be used as a template to make new.

02:39 So you can see now after second round you have again still two out of four hybrid 50 percent.

02:44 And then you have another 50 percent.

02:46 These two are made universally with n14 with red color.

02:51 So this tells us this is a semi -conservative model.

02:54 50 percent hybrid 50 percent n14 only.

03:05 This tells us this whole model we called it semi -conservative.

03:16 Which means the old strand, old dna strand split and each used as a template to make new strand.

03:23 So now if we look at all the options the first one is right...

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