ATAR Notes: Forum

HSC Stuff => HSC Science Stuff => HSC Subjects + Help => HSC Biology => Topic started by: nouribrahim on July 17, 2016, 01:11:40 am

Title: BIOLOGY QUESTIONS (Help needed)
Post by: nouribrahim on July 17, 2016, 01:11:40 am

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´

Title: Re: BIOLOGY QUESTIONS (Help needed)
Post by: CinnamonTea on July 17, 2016, 01:18:51 am

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?

Title: Re: BIOLOGY QUESTIONS (Help needed)
Post by: nouribrahim on July 17, 2016, 01:22:03 am

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

Title: Re: BIOLOGY QUESTIONS (Help needed)
Post by: heids on July 17, 2016, 01:22:21 am

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.

Title: Re: BIOLOGY QUESTIONS (Help needed)
Post by: CinnamonTea on July 17, 2016, 06:40:00 am

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

Title: Re: BIOLOGY QUESTIONS (Help needed)
Post by: vox nihili on July 17, 2016, 10:45:38 am

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.