Expert: Florence M Rollwagen - 6/21/2009

Question
Transcription: During the process of transcription, the information in the DNA codons of a gene is transcribed into RNA.

Suppose that gene X has the DNA base sequence 3’-TACCCTTTAGTAGCCACT-5’.

Question: What would be the base sequence of RNA after transcription occurs?

Translation: During protein synthesis at the ribosome, the base sequence of the mRNA codons is translated to the amino acid sequence of a protein.

Question: Using the mRNA that you transcribed above, use the genetic code table to determine the resulting amino acid sequence? Turn this in.

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

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

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

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

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

Question: Then, explain why a change in amino acid sequence might affect protein function. Turn in your answer.

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

Original sequence       3'- TACCCTTTAGTAGCCACT-5’

Mutated sequence 1) 3’-TACGCTTTAGTAGCCATT-5'

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

Answer
Hi Tammy:  This is obviously a homework question, but I'll send you to a couple of websites that will help.

The University of Utah has a great genetics site:
http://learn.genetics.utah.edu/

To transcribe and translate a gene look here:
http://learn.genetics.utah.edu/content/begin/dna/transcribe/

Give these tools a try and if you still have questions, email back.

FM Rollwagen, PhD