Critter
Project
Construct a Critter
Proteins roles range from catalyzing chemical reactions to providing movement and support.
Because of this proteins have a variety of structures. Differences among proteins are the result
of their amino acid sequence.
The amino acid sequences for proteins are coded for in each individual organism’s DNA in
segments called genes. In a process known as transcription, the DNA code for a protein is
copied by the messenger RNA (mRNA) in the nucleus of the cell. The mRNA then carries the
copy of the code to ribosomes in the cytoplasm of the cell.
The process of translation occurs when a second type of RNA, called transfer RNA (tRNA),
brings the amino acids to the ribosomes in the order specified in the mRNA. The ribosomes
function is to join the amino acids in the correct order to form the protein.
In this activity, you will simulate protein synthesis and determine the traits of fictitious animals
called critters. Critters have two chromosomes, each containing four genes. Each gene (A-H) is
responsible for the proteins that create a certain trait.
Procedure:
Determine the trait for Gene A of your critter by completing the box labeled Gene A in the Data
Table. Note the DNA sequence and then list the corresponding mRNA codons in the space
provided.
Determine the sequence of amino acids by matching the mRNA codons to the specific amino
acids found in Table 1. List the amino acid abbreviations in the space provided in the data table,
using a hyphen to separate each amino acid.
Use Table 2 to identify the trait that matches the amino acid sequence. Record this information
in the Data Table.
Repeat steps 1 – 3 for the remaining traits.
Using all 8 traits, sketch a diagram of your critter.
Example
Gene Z
DNA
CTC ACG TTC
mRNA
GAG UGC AAG
amino acid
sequence
GLA CYS LYS
trait
female
Observations
Data Table
Gene A
DNA
mRNA
Gene B
AAC TTA TAC GTT
______________________
DNA
mRNA
GGG CTC
______________________
amino acid
sequence ______________________
trait
______________________
amino acid
sequence ______________________
trait
______________________
Gene C
DNA
GGG AAG TGA
mRNA ______________________
Gene D
DNA
GTG AAC GTT ATG
mRNA ______________________
amino acid
sequence ______________________
amino acid
sequence ______________________
trait
______________________
trait
______________________
CAC ACG TCG
______________________
Gene F
DNA
mRNA
CCC CGT ACC ACG
______________________
Gene E
DNA
mRNA
amino acid
sequence ______________________
amino acid
sequence ______________________
trait
trait
______________________
______________________
Gene G
DNA
TAA GCG
mRNA ______________________
Gene H
DNA
CTA TTC TTA
mRNA ______________________
amino acid
sequence ______________________
amino acid
sequence ______________________
trait
trait
______________________
______________________
Table 1
mRNA codon
GAU
AUG
UUG
GAG
UGG
CAA
AAG
UAC
AAU
CCC
UGC
UUC
ACU
CAC
AUU
GCA
CGC
GUG
AGC
GGG
Amino Acid
aspartic acid
methioine
leucine
glutamic acid
tryptophan
glutamine
lysine
tyrosine
asparagine
proline
cysteine
phenylalanine
threonine
histidine
isoleucine
alanine
argentine
valine
serine
glycine
Table 2
Amino Acid Sequence
PRO-PHE-THR
PRO-LEU-THR
ASP-LYS-ASP
ASP-LEU-ASN
PRO-GLU
VAL-CYS-SER
GLA-CYS-LYS
ILE-ARG
PRO-ALA-TRP-CYS
GLY-ALA-TRP-CYS
LEU-ASN-MET-GLU
LEU-ASN-MET-ISO
HIS-LEU-GLU-TYR
VAL-PHE-GLU-TYR
Amino Acid Abbreviation
ASP
MET
LEU
GLU
TRP
GLU
LYS
TYR
ASN
PRO
CYS
PHE
THR
HIS
ILE
ALA
ARG
VAL
SER
GLY
Trait
small nose
big nose
freckles
no freckles
four-legged
male
female
four antennae
blue fur
orange fur
plump
skinny
purple eyes
yellow eyes
Sketch:
Questions:
1. Where in the cell:
a. are the DNA instructions located?
b. does transcription occur?
c. does translation occur?
2. Describe three similarities and three differences between DNA and RNA.
3. Why is specific base pairing essential to the processes of transcription and translation?
4. How could the change in one DNA nucleotide alter the protein formed?
5. Suppose you knew the sequence of amino acids in a protein. How could you determine the
DNA sequence for that gene?
6. Create two additional traits for your critter. Give their DNA sequences, the mRNA codons
and the resulting amino acid sequences.