How Does DNA Determine the Traits of an Organism?
You have just won a Nobel prize for discovering the first extraterrestrial life! Snorks were discovered on
the planet Dee Enae in a distant solar system. Surprisingly, their genetic material is also DNA and they
carry out the central dogma just as organisms do on Earth. Snorks only have one chromosome with 6
genes on it. You job is to analyze the genes of its DNA and determine what traits it has.
Amino Acid Sequence
Trait
Thr-Gln-Tyr
hairless
Leu-Arg-Leu
hairy
Thr -Ala-Ala
plump
Tyr –Asp -Cys
skinny
Ser- Arg - Gly
Ser – Arg- Val
4 legged
Ser -Arg - Arg
2 legged
Ala-Val-Lys
round head
Gly- Arg - Lys
block head
Phe- Lys - Lys
no tail
Phe - Asn - Lys
tail
Gly-Met-Arg
slanted eyes
Gln- Met - Met
wide round eyes
Ile- Ile -Leu
male
Ile - Ile -Asp
female
no nose
Observations and Analysis of Snork DNA
You are given a chromosome from a Snork with the following sequence. Each gene has
only 3 amino acids. Your job is to determine the sequence of amino acids for your
specimen. Write the complimentary mRNA, tRNA, the amino acid sequence it codes for
and the related trait in the chart below.
Gene
DNA
mRNA
ACTCAATAT
TACGACTGT
UGAGUUAUA
1
2
tRNA
ACUCAAUAU
Amino
Acid
Trait
Thr – Gln Tyr
hairless
3
4
5
AGCAGGGTC GCCGTGAAA TTTAACAAG
6
ATTATACTA
Now, what would happen if there were mutations (changes) in the Snork’s DNA (gene 2,
3, 5, and 6)? Fill in the table below using the changes described:
Gene
DNA
Mutation
mRNA
1
2
3
4
5
6
ACTCAATAT TTACGACTGT AGCAGGGGC GCCGTGAAA TTCAACAAG ATATACTA
tRNA
Amino Acid
Trait
Draw your Snorks!
BEFORE MUTATION
AFTER MUTATION
Questions
1. What is the name of the step that copies the information in DNA into a strand of mRNA?
Where does it take place in the cell?
2. What is the name of the step that uses mRNA to make protein? Where does it take place
in the cell?
3. How does DNA provide instructions for life? (DNA provides instructions to make proteins?
How do proteins control life?)
4. Some proteins need to leave the cell. What organelle processes proteins before they are
secreted?
5. How are proteins affected by DNA mutations?
6. Does a mutation always change the protein? If not, give an example of a mutation that
would not change the protein.