Part 1: Genetics – From Genes to Proteins,Mutations (Chapter 10) Overview : Gene

Question

Part 1: Genetics – From Genes to Proteins,Mutations (Chapter 10)

Overview: Genetic information in DNA istranscribed to RNA and then translated into the amino acid sequenceof a Protein.

A) Step 1 - Transcription: During the processof transcription, the information in the DNA codons of a gene istranscribed into RNA.

Suppose that gene X has the DNA base sequence3’-TACCCTTTAGTAGCCACT-5’.

Question: What would be the base sequence of RNA aftertranscription occurs? Turn this in.

(In this particular example, assume that the RNA product doesnot require processing to become mRNA. In other words, thetranscribed RNA becomes the mRNA sequence.)

B) Step 2 - Translation:During protein synthesis at the ribosome, the base sequence of themRNA codons is translated to the amino acid sequence of aprotein.

Question: Using the mRNA that you transcribedabove, use the genetic code table to determine the resulting aminoacid sequence. Turn this in.

And, turn in the answer to these questions:

What is the significance of the first and last codons?What meaning do these codons have for proteinsynthesis?

C) Mutations: A mutation is defined as a changein the base sequence of DNA. This may occur as a“mistake” in DNA replication, for example.

Suppose that during DNA replication, two mutant DNA sequencesare produced as shown below.

For the 2 mutated DNA sequences, you will investigate how thesechanges might affect the sequence of amino acids in a protein.

Question: For each of the two, you will need to firsttranscribe the mRNA, and then use the genetic code table todetermine the amino acid sequence.

Turn these in, and state whether the protein sequencechanges for each.

Question: Then, explain why a change in amino acidsequence might affect protein function. Turn in youranswer.

Here is the original sequence, followed by two mutatedsequences, 1 and 2:

Original sequence      3'- TACCCTTTAGTAGCCACT-5’

Mutated sequence 1) 3’-TACGCTTTAGTAGCCATT-5'

Mutated sequence 2) 3’-TAACCTTTACTAGGCACT-5’.

Explanation / Answer

Mutated sequence 1) 3’-TACGCTTTAGTAGCCATT-5'

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