Question

a) Complete the diagram on the right to illustrate the interaction pattern in the DNA major groove for the sequence: Strand #1: 5’- TGACGTCA - 3’

Complete the sequence for the complementary Strand #2.

Copy/paste, arrange the provided symbols for hydrogen-bond and hydrophobic interactions indicate arrangements.

b)The 5’- TGACGTCA - 3’ sequence normally binds to the transcription factor AP-2.

What would happen to the interaction surface on the DNA if the sequence was mutated to: 5’- TGAGCTCA - 3’ ?

What would happen to AP-2 binding?

Answer 1

Ana-a Sequence of Dna provided-

Strand-1 5'- TGACGTCA-3'

NOW, its complementary strand will be like this. We know chargaff's rule. Adenine binds with Thymine with 2 hydrogen bonds and guanine binds with cytosine with three hydrogen bonds.

Strand-2 3'- ACTGCAGT-5'

The hydrogen bonding is between the two strand formed between the nitrogenous bases. While hydrophobic interactions are among the strands individually itself. The sugar bases of purine and pyrimidine are being bound together by hydrophobic interactions while two strands are kept tight together by hydrogen bonding.

Ans- b Transcription begins on the 3'-5' strand of Dna and a mrna is being synthesized in this process.

  5'- TGACGTCA-3'

So from this one,

3'- ACTGCAGT-5'

mrna produced- 5'- UGACGUCA-3'

Now if the sequence is mutated like this

5’- TGAGCTCA - 3’

3'- ACTCGAGT-5'

mrna produced- 5' - UGAGCUCA-3'

If the mutation happens, then the working efficiency of ap-2 transcription factor decreases. This is because there is many chances of occurance of other nitrogenous bases at binding place of one. For eg it can also bound to TGCATGCA, or CACATG. But if this sequence ia specifically given , and no other assumptions are taken, then the transcription factor cannot bind properly.

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