Genetics

Turnoaround time –

4

hours

 

Transcription/Translation:  Consider the gene below:

 

3’ 

1 2 3

4

5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21

 5’

  T A C

C C T T A A C C A A T

G

A G T A T T

 

       5’    A T G G G A A T T G G T T A C T C A T A A   3’    

1.      

In the space below, write the nucleotide sequence for the mRNA encoded by the gene.  Be sure to indicate the 3′ and 5′ ends for the mRNA.

 

2.      

Circle the translation start codon in the mRNA above.

 

3.      

What is the nucleotide sequence in the anti-codon loop of tRNA that is complementary to the start codon? ______.  Indicate the 3′ and 5′ side of the anti-codon region.

4.      

What amino acid does the start codon specify?  ________

5.      

Circle the translation stop codon in the mRNA strand above.

6.      

Using a codon table (see table in your text), in the space below write the predicted sequence of amino acids for the polypeptide encoded by this gene.

                               

Mutations:

 

1.       Assume that there is a mutation in the DNA in nucleotide 6 and it is changed from T, which occurs in the original strand, to A as shown.   In the space below, write the amino acid sequence of the polypeptide that would result.  How will this mutation affect the final protein?

 

3’  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21  5’

  T A C C C A T A A C C A A T G A G T A T T  

 

2.       This is an example of a(n) _______________ mutation.

a.     
 point         b.  frame shift      c.  missense

 

3.       Assume that there is a mutation in the DNA in nucleotide 15 (red) and it is changed from G, which occurs in the original strand, to C as shown.   In the space below, write the amino acid sequence of the polypeptide that would result.  How will the mutation affect the final protein?

  3’  1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21  5’   T A C C C A T A A C C A A T C A G T A T T    

4.       This is an example of a(n) _______________ mutation.

b.     
 point         b.  frame shift      c.  missense

 

5.       Assume that two nucleotides, T and G are inserted in the original DNA strand between nucleotides 4 and 5.  How will this affect the polypeptide?  Write the sequence of amino acids in the protein below.

  3’  1 2 3 4     5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21  5’   T A C C T G C T T A A C C A A T G A G T A T T        

6.       Which one of the following would be likely to have the least impact on the final protein? (Explain)     a.  an insertion involving one nucleotide        b.  an insertion involving two nucleotides     c.  an insertion involving three nucleotides

 

7.      
Assume that you isolate the polypeptide that was made in question #4 from a piece of “chicken-fried cat.”  To your surprise the protein begins with glycine!  What’s the deal?     a.  the DNA, like a sleazy cat, lied     b.  a methionine amino acid was probably clipped off the protein after translation     c.  RNA polymerase made a mistake and inserted an incorrect nucleotide.