Reporting Category 2
Mechanisms of
Genetics
Station 8
Changes to the Genetic Code
Essential Question-Bell Ringer
Humans have approximately 75,000 to
100,000 genes in a typical cell. A
single gene contains about 10,000
nitrogen base pairs. How is it possible
for a single mutation to one of these
base pairs to cause a life-threatening
condition?
Journal
Essential Question answer:
Nitrogen base combinations code for
amino acids, which produce proteins.
If a mutation to one of the base pairs
affected a protein that was vital to the
functioning of a crucial organ or
system, this mutation would cause the
organ or system to fail.
Journal
Pre-Review Question
During the process of protein synthesis, a
section of the DNA molecule is copied into
which other molecule?
A.Nucleic acid
B.Cytoplasmic DNA
C.Messenger RNA
D.Transfer RNA
Pre-Review Question
In messenger RNA, each codon specifies a
particular:
A.Nucleotide
B.Purine
C.Amino acid
D.Pyrimidine
Pre-Review Question
True or False
Any change in the genetic sequence (DNA)
that affects the genetic information is
referred to as a mutation.
True
Pre-Review Question
Type of mutation that takes place when a
base codon is changed but both code for the
same amino acid:
A.Silent mutation
B.Transition mutation
C.Transversion
D.Deletion
Lab Activities
You will now go to the lab and complete the
activities for todays topics…
Genetic Code Wheel
Write and answer the question in your journal (Include
the DNA sequences)
1. Using the mRNA Genetic Code chart, determine
the name of the amino acid each codon
represents.
• AUG CCA ACA GUG AGA UUA CAG AAA UCG UAA
Start, proline, theorine, valine, arganine, leucine,
glutamine, lysine, serine, stop.
This will serve as your original strand.
2. What does this chain of amino acids represent?
A polypeptide chain or a protein strand.
Write and answer the question in your journal (Include
the DNA sequences)
3. Some genetic mutations are caused by changes
in the bases of some codons. Compare the two
sequences below and compare them to the
original sequence. Can you identify which
codon was changed and what the new amino
acid will be?
• AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA
• AUG CCA ACA GUG AGA UUG CAG AAA UCG UAA
Answer
• AUG CCA ACA GCG AGA UUA CAG AAA UCG UAA
Uracil has been replaced with cytosine
This will change the amino acid from valine to alanine.
• AUG CCA ACA GUG AGA UUG CAG AAA UCG UAA
Alanine has been replaced with guanine.
However, this still codes for the same amino acide.
This is known as a silent mutation.
Write and answer the question in your journal (Include
the DNA sequences)
4. If an additional base is added it it called a
frameshift. Compare the original strand to the
strand below and find the insertion. How many
amino acids would be affected?
AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A
Write and answer the question in your journal (Include
the DNA sequences)
4. If an additional base is added it it called a
frameshift. Compare the original strand to the
strand below and find the insertion. How many
amino acids would be affected?
AUG CCA ACA UGU GAG AUU ACA GAA AUC GUA A
Start, proline, theorine, cysteine, glutamic acid,
isoleucine, threonine, glutamic acid, isoleucine,
valine, nothing.
5. What is the significance of this frame-shift
mutation for the structure of the protein?
After the mutation, 7 of the 10 codons now code for a
different amino acid than the original sequence did. In
addition, a single adenine (A) base ends the strand.
This frame-shift mutation will cause massive changes
in the types of protein produced by the new strand.
What I need to remember….
• Mutations are changes in DNA that can be
inherited.
• Certain codons are responsible for starting the
production of a protein, and other codons stop the
process.
• Mutations occur when bases are added or deleted
and when segments of DNA are missing.
• Not all mutations are harmful—some are very
beneficial.
Post Review Question
What type of point mutation is illustrated in
the table below?
Original Strand
Mutated Strand
DNA
TAC GTA CGG TAA
TGC GTA CGG TAA
mRNA
AUG CUA GCC AUU
ACG CAU GCC AUU
Amino acid
Met His Ala Iso
Thr His Ala Iso
A. Substitution
B. Silent
C. Deletion
D. Insertion
Post Review Question
Identify the following mutation:
A.Translocation
B.Deletion
C.Inversion
D.Duplication
Post Review Question
Identify the following mutation:
A.Translocation
B.Deletion
C.Inversion
D.Duplication