Transcription and Translation Exercise
1. A portion of the kernel pigment gene (in corn) is shown below. This portion of the
gene encodes the very first part of the kernel pigment protein. Use the base sequence for
mRNA to complete the columns on the following table. Be sure to include the polarity of
the DNA and tRNA strands.
DNA
5’
mRNA
3’
G
G
T
C
T
A
T
G
T
C
A
G
G
C
C
A
C
C
T
G
C
C
G
C
G
G
A
C
T3’
C
C
A
G
A
T
A
C
A
G
T
C
C
G
G
T
G
G
A
C
G
G
C
G
C
C
T
G
A5’
Complement
Gene/template
5’
G
G
U
C
U
A
U
G
U
C
A
G
G
C
C
A
C
C
U
G
C
C
G
C
G
G
A
C
U3’
tRNA
C
C
A
G
A
U3’
A
C5’
A3’
G
U5’
C3’
C
G5’
G3’
U
G5’
G3’
A
C5’
G3’
G
C5’
G3’
C
C5’
U3’
G
A5’
2. Describe the relationship between the gene sequence and the mRNA sequence.
The gene sequence and the mRNA sequence are complements of each other.
3. Describe the relationship between the gene sequence and the tRNA sequence.
They are the same except RNA contains U’s while DNA contains T’s.
4. If the coding region of a protein coding gene contains 300 DNA nucleotides, how
many amino acids will be used in protein synthesis?
99 amino acids. Every three nucleotides = 1 amino acid, so 300/3 = 100, but the stop
codon does not code for an amino acid, therefore 99 amino acids.
5. If a protein has 150 amino acids, how many DNA nucleotides would make up the
coding region of the gene?
150 x 3 = 450, plus one codon for stop, 450 + 3 = 453.
6. What is the amino acid sequence for the very first part of the kernel pigment protein in
the exercise above?
Met-Ser-Gly-His-Leu-Pro-Arg-Thr
7. The allele of the gene above is dominant and codes for red kernel pigment (it is
designated as R). Another allele of this gene, the r allele (which is recessive), codes for
white kernel pigment and is the result of a mutation in the R allele. In the r allele, the
second nucleotide (base) in the second codon of the open reading frame (or coding
region) is an adenine.
What does the second codon in the r allele code for?
UCA becomes UAA = STOP
8. A protein has the following amino acid sequence. Construct a DNA nucleotide
sequence of this portion of the gene.
Phenylalanine-Glycine-Glycine-Alanine-Proline-Valine-Asparagine-Alanine
There are multiple correct answers for this.
9. If you compared your sequence to one constructed by a classmate, would you expect to
see any variations? What would be the reason for the difference?
This is due to the redundancy or degeneracy of the code. (multiple codons code for
the same amino acid)
10. Complete the following table:
Nucleotide Components and Function
Nucleic Acid Type
DNA
deoxyribose
Name of the sugar present
in nucleotides
Name of bases present in
nucleotides
Function of the type of
nucleic acid
Describe the relative size
and number of stands in
each of the nucleic acids
Where can you find each
of these in a eukaryotic
cell?
mRNA
tRNA
ribose
ribose
Adenine, Guanine,
Cytosine, Uracil
Adenine, Guanine,
Cytosine, Uracil
Molecular
middleman used in
protein synthesis.
Very, very
large.
Copy an of
individual gene,
used as
instructions to
synthesize a
protein.
Fraction of the
genome size.
nucleus
Cytosol
cytosol
Adenine,
Guanine,
Cytosine,
Thymine
Storage of
genetic info
Relatively small.