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maskman`

i have a question by cambrige Help please:)

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32 In a genetic engineering experiment a piece of double-stranded DNA containing 6000 nucleotides
coding for a specific polypeptide is transcribed and translated.
What is the total number of amino acids in this polypeptide?
A 500 B 1000 C 2000 D 3000
33 Bacteria were grown in a medium containing 15N. After several generations, all of the DNA
contained 15N. Some of these bacteria were transferred to a medium containing the common
isotope of nitrogen, 14N. The bacteria were allowed to divide once. The DNA of some of these
bacteria was extracted and analysed. This DNA was all hybrid DNA containing equal amounts of
14N and 15N.
The remaining bacteria were left in the medium with 14N and allowed to divide one more time. The
DNA of some of these bacteria was extracted and analysed.
What is the composition of this DNA?
A 25 % hybrid DNA
B 50 % hybrid DNA
C 75 % hybrid DNA
D 100 % hybrid DNA

what are your answers and why?

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Post in the homework section next time!

 

I'd answer 2000 for the first one because 3 nucleotides = one amino acid.

 

For the second one I'd answer 50% of the next generation would be hybrid. The previous generation were all hybrids that have one strand of 15N and one strand of 14N so the outcome after replication would be double stranded 14N/14N in one daughter and 15N/14N in the other daughter, meaning 50% offspring are hybrid.

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We generally do not provide outright answers. Rather, our goal is to have students try it themselves first and then guide them towards answers.

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Hi,the question seems to be intellectual but i will suggest you to at least find the answer of your own and then i can help you later with proper guide.

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