When amino acid sequences of insulin isolated from different organisms were determined.....see details please.

Question

When amino acid sequences of insulin isolated from different organisms were determined, some differences were noted. Alanine was substituted for threonine. Serine was substituted for glycine, and valine was substituted for isoleucine. For each amino acid indicate the original mRNA codon, then explain the single base substitution that produced the change.

Threonine__________ > Alanine__________

Glycine__________ > Serine__________

Isoleucine__________ > Valine__________


I dont know how to answer this question! hope some1 can help me. Thank you!

Answer 1

Look in your textbook or online to see a chart of the mRNA codons. There's one at: http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/C/Codons.html#rna_codons

I'll help you with the first one.

Threonine is brought to one of the following codons:
ACA
ACU
ACG
ACC

Alanine is brought to one of these codons:
GCA
GCU
GCG
GCC

In order to get alanine instead of threonine, mRNA just had to have a G in place of an A.

mRNA's A would have been transcribed from DNA's T.
mRNA's G would have been transcribed from DNA's C.

So the single base substitution in the DNA was substituting C for the T that should have been in DNA.

Answer 2

Do a google search for the "amino acid code" (under google images)

What you'll see are different combinations of the 4 mRNA nucleotides. Each combination produces a different amino acid residue to be added to the growing protein chain on the ribosome.

From the question, you should see that the three letter code for Threonine is very similar to Alanine, except for ONE letter. Find that letter. That's your answer.

Repeat for Gly vs. Ser, and Isoleucine vs. Valine

If you take further courses in biochemistry, biology etc, you will be forced to get VERY familiar with this. So do a google images search for the "amino acid code'' and save it to your computer for future reference.