Name: ________________________
Date: _____________
5A Gene Expression
Study Guide
Part I
1. Compare DNA and RNA, include BOTH structure and function.
DNA
Double
stranded
Contains
deoxyribose
sugar
Contains
thymine
RNA
Both
Have A, C, G
Nucleic Acids
Made of
nucleotides
Single
stranded
Contains
ribose sugar
Contains
uracil
2. What are the roles of the three types of RNA? Fill in the table:
Type of RNA
Messenger RNA
Ribosomal RNA
Transfer RNA
Picture
Function
Use the following gene to complete the tasks below:
DNA/gene
T A C
T T C
G G A
A T A
G C A
A C T
Transcribe the gene into mRNA
____AUG___|____AAG____|____CCU_____|_____UAU____|______CGU___|____UGA___
Translate the mRNA into a polypeptide
_____Met__|____Lys_____|_____Pro_____|_____Tyr_____|_____Arg_____|____stop____
What are the tRNA anticodons that match with the mRNA codons?
_____UAC__|____UUC____|_____GGA_____|_____AUA___|_____GCA____|_____ACU__
3. Complete the following table:
Location
Starting Molecule
Product
nucleus
DNA
mRNA
Ribosome
mRNA
Polypeptide (protein)
Transcription
Translation
4. What enzyme allows for transcription to occur? ______RNA Polymerase______
5. What is the first codon read on an mRNA strand called? __Start Codon___ What three letters make this codon?
____AUG____
6. What is the codon called that tells the ribosome that the polypeptide is complete? ____Stop Codon___
7. tRNAs bring in the correct amino acids according to the message in the mRNA. This happens because each tRNA
has an ___anticodon____ that pairs with a specific ____codon____ on the mRNA.
8. What types of bonds connect the amino acids in the polypeptide? _____peptide_______
9. Use the word bank to label the diagram below:
mRNA
tRNA
start codon
stop codon
anticodon
ribosome
polypeptide
tRNA
polypeptide
anticodon
ribosome
mRNA
Start codon
Stop codon
10. Think!!
a. A mRNA strand with 66 nucleotides codes for a polypeptide __22___ amino acids in length.
b. A protein 300 amino acids in length was made from an mRNA strand ___900____ nucleotides in length.
Part II
1. What are the three types of gene mutations? __substitution, insertion, deletion__________________________
2. Create each of the gene mutations one at a time using the gene below. EACH TIME MAKE THE MUTATION AT
THE 4TH BASE. Show how it will affect the resulting polypeptide.
Original Gene:
TAC
GTG
AAC
GCA
Transcribe the original: AUG
CAC
UUG
CGU
Translate the original:
His
Leu
Arg
Met
Substitution
Insertion
Deletion
Gene with mutation
Resulting mRNA
Resulting polypeptide
3. Which two gene mutations are frameshift mutations? ___insertion and deletion_____________________
4. Why are these more problematic types of mutations? ____These shift all the nucleotides over, and change all
the codons after the mutation, therefore changing all the amino acids in the resulting polypeptide. ___________
5. Describe each of the chromosomal mutations shown below:
- ___A section of the chromosome is missing____
-___A section of a chromosome is copied twice (doubled)____________________________
-____Two sections of a chromosome switch places_________________________
-____A section or sections of one chromosome moves to another chromosome__________
6. Why can some mutations be helpful, others harmful, and others make no difference at all?
____Helpful mutations lead to better functioning proteins, harmful mutations lead to non-functioning proteins,
mutations in the third nucleotide of a triplet can potentially have no effect on the protein if the codon still
translates to the same amino acid. ____________________________________________________________
7. Roughly how much of the DNA codes for protein? ___2%__What is the rest of the DNA called? _Non-coding___
8. What does it mean for a certain gene to be “turned on”? ______If a gene is turned on it is actually being
expressed, meaning that its message will be transcribed and translated into a protein. _____________
9. Turning on and off genes allows cells to ___specialize_________ (have a certain job role).