Assignment details for part one: Transcribe and translate EACH of the three foll

Question

Assignment details for part one:

Transcribe and translate EACH of the three following DNA gene sequences. Turn these in using the graphic organizer. The letters represent the DNA N-base sequences of the genes.

The first is the original gene. The next two are mutations of the original. Note that the changes (mutations) are shown in red.

Original Gene sequence 3'-T A C C C T T T A G T A G C C A C T-5

Mutated gene sequence 1 3’-T A C G C T T T A G T A G C C A T T-5'

Mutated gene sequence 2 3’-T A A C C T T T A C T A G G C A C T-5’

Also, answer the following questions:

•What is the significance of the first and last codons of an mRNA transcript?
•What meaning do these mRNA codons have for protein synthesis?
•Did the mutations result in a change in the final proteins? If so, describe the change.
•In general, why might a change in amino acid sequence affect protein function?

Explanation / Answer

Original Gene sequence 3'-T A C C C T T T A G T A G C C A C T-5'

3'-A U G G G A A A U C A U C G G U G A-'5 : this is the mRNA strand that runs through the ribosomes for translation.

Mutated gene sequence 1 3’-T A C G C T T T A G T A G C C A T T-5'

3'-A U G C G A A A U C A U C G G U A A-5'

Mutated gene sequence 2 3’-T A A C C T T T A C T A G G C A C T-5’

3'-A U U G G A A A U G A U C C G U G A-5'

Alrighty, so the second sequence that I wrote out is the mRNA that is transcribed from the DNA and sent to the ribosomes for translation. Remember that the T is replaced by a U when dealing with RNA. When it gets to the ribosome, this new strand is processed into amino acids by three's. I switched off underlining and bolding each triplet of nucleotides so you can see what the ribosome would be reading.

Each triplet, or codon, codes for a certain amino acid. From the looks of your question, your teacher must have given you a sheet that tells you which amino acids code for a certain triplet. Use that to figure out what amino acids would be translated from the strands.

1. When you decode the strans, you should find that the first and last codons are start and stop codons. They tell the ribosome to START translating at that point and then STOPPING at the other. Notice that there are several different codons that code for start and stop.

2. Each codon codes for an amino acid, which is the primary structure of a protien.

3. These mutations were all point mutations, not frame shifting ones that affected the whole protien. These point mutations only affect one codon, which can sometimes still code for the same amino acid as the non-mutated strand. I'm leaving this one up to you because I can't decode the strands. Just compare the end results of the amino acid strands and see if the codons coded for the same amino acids or if they changed them.

4. In general, the affect of one amino acid can change the function of a protien, possibly making it a different protien than the one previously desired which can cause other problems. Most of the time they turn into unaffective protiens that end up being dismantled and turned back into scraps for the next translation of mRNA.

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