Problem Set #5

Modern Biology 03-121

Spring 98

Due Wed. 4/8

answers are in boldface type

1.The base sequence of the gene coding for a short polypeptide is

CTACGCTAGGCGATTGACT.

What would be the base sequence of the mRNA transcribed from this gene? (3 pts)

GAUGCGAUCCGCUAACUGA

What would be the amino acid sequence of the polypeptide chain translated from this mRNA? (hint: what is the start codon?) (3pts)

met-arg-ser-ala-asp-stop

2. The nucleotide sequence of a DNA codon is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a transfer RNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon? (3 pts)

GUA

3. What is an Okazaki fragment ? Why is it important? (3 pts)

Short polynucleotide fragments which will eventually be joined to form the lagging strand in the process of DNA replication. They occur because both DNA strands are replicated at once, yet synthesis must occur in the 5'---3' direction. Thus, one strand must be synthesized in short pieces.

4. Draw the complete chemical structure of the trinucleotide 5'-ATG-3'. Label the 2 phosphodiester linkages. Use the back of this sheet. (3 pts)

see your text