BIOLOGY QUESTIONS (Help needed)

[nouribrahim]

So i believe the answer is A but the marking scheme says B
can someone explain please?
A DNA strand has the following bases:
5´ - CTTAAG - 3´
What are the bases on the complementary strand?
(A)
3´ - GAATTC - 5´
(B)
3´ - GAAUUC - 5´

[CinnamonTea]

Yeah the answer is B
1. Complemenatry bases are A with T and C with G
2.  U for uracil replaces Thymine during protein synthesis (to be exact during transcription on mRNA strand)
Where did you find the question?

[nouribrahim]

But wouldnt it Be Uracil only if it was an RNA not DNA? because DNA doesnt have Uracil

[heids]

I'm pretty sure that 'complementary strand' means the other strand in the two-stranded DNA, rather than the RNA strand produced during transcription.

Thus, this couldn't have uracil in it and so I'd say the answer was actually A.

[CinnamonTea]

Yeah I agree Heidiii, since it mentions Complemenatry strand for the DNA and not the mRNA

[vox nihili]

Complementary strand can be RNA or DNA. If the question doesn't specify it, both answers are acceptable. I agree with those above that the question does imply that it's the complementary DNA strand, but given the question fails to say that specifically I don't understand how you can be expected to read minds.




Just as an aside, and totally not involved in your course, but the strength of the interaction between RNA and DNA is actually stronger than DNA:DNA.