CHNOPS- Simulating Gene Expression
Objectives:
Before doing this assignment you should be able to:
 define gene
 state where in the cell transcription and translation take place
 describe the structure and function of DNA and RNA in inheritance
After doing this assignment you should be able to:
 distinguish between transcription and translation
 describe the role of mRNA and tRNA in gene expression
 model gene expression from transcription to the level of phenotype (trait)
 relate genes and alleles to genotypes and phenotypes
Background:
Genes are the units that determine inherited characteristics, such as hair color and blood type.
Genes are the lengths of DNA molecules that determine the structure of polypeptides (the building
blocks of proteins) that our cells make. The sequence of nucleotides in DNA determines the sequence
of amino acids in polypeptides, and thus the structure of proteins.
In a process called transcription, which takes place in the NUCLEUS of the cell, RNA
Polymerase reads and copies the DNA’s nucleotide sequences in the form of a complementary RNA
molecule. Then the mRNA carries this information to the RIBOSOMES, where translation takes
place. The code, in DNA or mRNA, specifies the order in which the amino acids are joined together to
form a polypeptide. The code words in mRNA, however, are not directly recognized by the
corresponding amino acids. Another type of RNA called transfer RNA (tRNA) is needed to bring the
mRNA and amino acids together. As the code carried by mRNA is “read” on a ribosome, the proper
tRNAs arrive in turn and give up the amino acids they carry to the growing polypeptide chain. The
process by which the information from DNA is transferred into the language of proteins is known as
translation. Transcription and translation together comprise the process called protein synthesis or
gene expression. The actual different gene sequences for the traits are the different forms of the
gene or alleles. The genotype is by definition what is encoded in the genes. It is the differences
between the forms of the genes that result in the differences between proteins, OR the absence of
certain functional proteins, that leads to different phenotypes.
Gene (allele1) = DNA sequence  mRNA sequence  amino acid sequence  protein  phenotype
***mutation***
Gene (allele2) = different DNA sequence  different mRNA sequence  different amino acid sequence  different or nonfunctional
protein  different phenotype
As scientists begin to sequence the genes of organisms found on Earth (and would attempt to
do with any extraterrestrial life discovered), they are learning more and more about the genome of
each species. This lab begins with a simulation involving the genome of a fictitious organism called a
CHNOPS for which scientists have sequenced 6 genes, arbitrarily identified as genes A, B, C, D, E,
and F.
What questions do you have after reading? Write them below, then complete the assignment.
If you have not answered your own questions, please either look in your notes or text for the
answers, or ask your teacher.
Name: _______________________ Per. _______ Date _______
1. Complete Figure 3 using information from Figures 1 & 2.
Figure 1. CHNOPS Codon Table
Figure 2. Alleles for Genes A-H in CHNOPS
tRNA Triplet
Amino Acid Number
CCC
1
CGA
2
15-12-13
CGC
3
6-6-10
AAC
4
6-6-4
GGG
5
AUC
6
AGG
7
5-7-8
AAA
8
9-8
UUU
9
9-4
CUA
10
GGA
11
GGU
12
UAU
13
AGC
14
ACC
15
Amino Acid
Sequence
15-11-13
14-2
Trait
Hair
11-3-2
Hairless
Purple Hair
Body form
Plump
Skinny
Leg number
(not identified)
12-7-8
Phenotype
4-Legged
No legs
Nose length
Long nose
Short nose
Freckled
No freckles
Freckles
Skin pigment
11-3-3
Purple skin
Orange skin
Figure 3. Traits for Genes A-F in a Specimen of CHNOPS
Gene A
DNA: ACC GGT TAT
Gene B
DNA:
Gene C
DNA:
mRNA: UGG CCA AUA
mRNA:
mRNA:
tRNA: ACC GGU UAU
tRNA: AGC CGA
tRNA:
AA sequence: 15-12-13
AA sequence:
AA sequence:
Phenotype – Purple Hair
Gene D
DNA:
Phenotype –
Gene E
DNA: GGT AGG AAA
Phenotype – no freckles
Gene F
DNA:
mRNA:
mRNA:
mRNA: UAG UAG UUG
tRNA:
tRNA:
tRNA:
AA sequence: 11-3-3
AA sequence:
AA sequence:
Phenotype –
Phenotype -
Phenotype -
Draw your CHNOPS in the box below illustrating all of its genetic characteristics.
ANALYSIS & CONCLUSIONS
1. Where do you think the name CHNOPS comes from?
2. Distinguish between translation & transcription.
3. What are the specific sites for transcription & translation in the cell?
4. How many tRNA nucleotides form an anticodon that will attach to the mRNA codon?
5. What role does mRNA play in gene expression? tRNA?
6. Suppose you knew the makeup of specific proteins in a cell. How would you determine the
particular DNA code that coded for them? (Hint: Given the trait, how would you find the DNA)
7. How could one change in a DNA nucleotide alter the formation of the translated protein? (An
example would be the difference between normal and sickle-cell hemoglobin)
8. Describe the three different types of mutations.
9. What does sense and nonsense mutations mean?