This question has been bugging me so hard.

[joseph95]

This Q was on my last chemistry sac.

What is the minimum number of nucleotides needed to code for a protein segment containing 15 amino acids?

The answe is 45. One mark question. Please explain.

[amilss]

Well three nucleotides code for an amino acid

So 15 amino acids contains (15x3) nucleotides = 45

[joseph95]

Can you explain to me the theory behind that? Obviously I get that it's 3 times 15. I just don't understand how 3 nucleotides can "code" for one amino acid. What does that actually mean?

[Aurelian]

Can you explain to me the theory behind that? Obviously I get that it's 3 times 15. I just don't understand how 3 nucleotides can "code" for one amino acid. What does that actually mean?

This is more biology than chemistry, and quite frankly that question shouldn't have been on your SAC. I really wouldn't worry about it in the slightest, but if you're curious, proteins are synthesised in organelles in cells called 'ribosomes'. You have mRNA - "messenger" RNA - which is just a strand of RNA. Then you have tRNA - "transfer" RNA - which consists of three nucleotides to which an amino acid is attached.  Hence you need a sequence of three nucleotides (a "codon") in a strand of RNA to code for one tRNA molecule (and, consequently, for one amino acid).

The below video explains visually far better than I could ever with just words;
http://www.youtube.com/watch?v=Ikq9AcBcohA

But again, do *not* worry about this for chemistry!

EDIT: Or even just the following diagram from wiki, since that video contains a fair bit of biological terminology;
http://upload.wikimedia.org/wikipedia/commons/0/0f/Peptide_syn.png

[joseph95]

Thanks Aurelian! I knew it was bullshit to be on our sac... I know it was only one mark but still

[Panicmode]

Actually, I'm pretty sure a basic understanding of transcription and translation is necessary for VCE chemistry exam. This question could theoretically appear on an exam.

[joseph95]

Nah.

[Aurelian]

Actually, I'm pretty sure a basic understanding of transcription and translation is necessary for VCE chemistry exam. This question could theoretically appear on an exam.

The study design only mentions;

• primary, secondary and tertiary structure of proteins and the function of protein catalysts
(enzymes);
• biochemical fuels including fermentation of sugars to produce ethanol;
• the structure and bonding of DNA and its applications in forensic analysis;
• use of proteins as markers for disease;

It really isn't within the scope of the study design.

[nooshnoosh95]

nah deffs not part of chem too much bio