Name: _______________________
SCI 1100 Science Seminar (Fall 2005)
Monday, October 3, 2:00-4:50 p.m.
1. In no more than 50 words, write down as much as possible what you know about
DNA. You should include brief answers to the following questions:
(a) What is a DNA molecule made up of?
(b) How would you describe the overall molecular structure of DNA?
(c) Where does DNA reside in a living organism?
(d) How does DNA function as the “blueprint of life”?
2. Among the four nucleotide bases A and T form a complementary pair, and so do C and
G. Write down the complementary string of nucleotide bases for the first row on the
second row of the table below.
G G A T C A A A C C T A G C G A G T C C C
3. Now I want to let you know that:
(a) The 2 complementary strands in a DNA molecule is always read in reverse directions.
Say, if the top strand from left to right, the bottom strand will be read from right to left.
(b) A gene is a segment of a DNA molecule that code for a particular protein (e.g.
hemoglobin, antibodies) of the organism.
In a gene, three consecutive nucleotide bases can function as a codon to code for one of
the 20 amino acids that make up protein molecules. Use a little math to figure out how
many possible distinct codons can exist?
Ans. _________________
4. If you get the correct answer to Question 3, you should realize that there are many
more possible codons than amino acids. So the mapping between codons and amino
acids must be a many-to-one function. This mapping is known as the “genetic code”
and it applies universally to all living organisms. Different codons coding for the
same amino acid are called synonymous codons. The genetic code is usually given in
the form of a table. Go to http://www.accessexcellence.org/RC/VL/GG/genetic.html
and http://www.math.utep.edu/Faculty/mleung/bioinformatics/aacodon.html and print
a genetic code table and an amino acid symbol table for yourself (the “U” in the
tables corresponds to the base “T” in DNA).
