Lesson 3.04
Mutations
3.01 Cell Division
While you wait to get started…
SC.912.L.16.17 – MITOSIS AND MEIOSIS
(EOC Practice)
Which of the following phrases best describes cancer?
B. multiple gene mutations on a chromosome of DNA
C. uncontrolled cell growth caused by mutations in genes that control the cell cycle
D. presence of genetic defects caused by hereditary disorders
3.01 Cell Division
While you wait to get started…
SC.912.L.16.17 – MITOSIS AND MEIOSIS
(EOC Practice)
Which of the following phrases best describes cancer?
B. multiple gene mutations on a chromosome of DNA
C. uncontrolled cell growth caused by mutations in genes that control the cell cycle
Cancer cells lack the ability to recognize and control cell growth and reproduction. As a result, they replicate again and again.
Let’s Review from 3.03
Identify the functions of the 3 types of RNA?
B. mRNA
C. rRNA
Let’s Review from 3.03
Identify the functions of the 3 types of RNA?
B. mRNA
C. rRNA
Let’s Review from 3.03
The sequence of DNA below is part of a gene. How many amino acids are coded for by this segment?
5' ATCAGCGCTGGC 3’
B. 8
C. 12
D. 14
Let’s Review from 3.03
The sequence of DNA below is part of a gene. How many amino acids are coded for by this segment?
5' ATC AGC GCT GGC 3’
B. 8
C. 12
Each section of three nucleotides codes for one amino acid. Since there are four triads here, this piece of DNA codes for 4 amino acids.
Flashback to protein synthesis…
Transcription:
Translation:
Codons:
A-A-G C-G-A C-U-U
Amino Acids:
______ _______ ______
The gene for large single eye is TTCGCTGAA.
Transcription:
Translation:
Codons:
A-A-G C-G-A C-U-U
Amino Acids:
______ _______ ______
The gene for large single eye is TTCGCTGAA.
Transcription:
Translation:
Codons:
A-A-G C-G-A C-U-U
Amino Acids:
______ _______ ______
The gene for large single eye is TTCGCTGAA.
Transcription:
Translation:
Codons:
A-A-G C-G-A C-U-U
Amino Acids:
______ _______ ______
The gene for large single eye is TTCGCTGAA.
Lys Arg Leu
The protein Lys-Arg-Leu creates a large single eye.
The Relationship Between Genes and Proteins
Genes are nothing more than instructions for building proteins.
What do proteins have to do with the color of a flower, a human blood type, or dimples?
The traits of any organism are the result of the proteins being built within the cells.
The answer is –
EVERYTHING!
On occasion cells make mistakes in copying their DNA.
An incorrect nitrogen base may be inserted, or a base may be skipped altogether.
These mistakes are called mutations.
Mutations are changes in the genetic material of a cell.
Mutant True or False
Mutant True or False
Chromosome mutations produce changes in the whole chromosome. There are 4 types of chromosome mutations.
Mutations may be either gene mutations or chromosomal mutations.
Gene mutations produce a change within a single gene.
Gene (Point) Mutations
Point mutations are changes in just one base pair of a gene.
These are called point mutations
because they occur at a single point in the DNA sequence.
There are Two Types of Point Mutations
Base Pair Substitutions:
One nitrogen base is changed to another.
Notice what happens when the “G” at the second base
is substituted with a “T”?
Base Pair Substitutions
2. It would affect just the one amino acid coded for by that codon.
3. If the substitution is in the 3rd position, it may not have any effect on the organism since there is some redundancy of codons.
1. A base pair substitution is the replacement of one nitrogen base with another.
Base Pair Substitutions: An Example
The codons for alanine are GCU, GCC, GCA, and GCG.
A point mutation at the third position would have no effect whatsoever.
The codon would still call for the amino acid alanine.
These are called silent mutations.
5. A switched amino acid may or may not have any effect on the proper functioning of that protein.
If the alteration of a single protein is in a crucial area, such as the active site on an enzyme, the protein will not function properly.
Base Pair Substitutions
The wrong amino acid would be called for and inserted into the polypeptide chain that is being manufactured.
Only that one amino acid would be affected.
What amino acid would be called for by the codon AAG?
What would happen if a “C” was substituted at the third position in this codon?
Practice Problem Questions:
What would happen if an “A” was substituted at the third position in this codon?
What amino acid would be called for by the codon AAG?
Answer: Lysine
What would happen if a “C” was substituted at the third position in this codon?
Practice Problem Questions:
What would happen if an “A” was substituted at the third position in this codon?
What amino acid would be called for by the codon AAG?
Answer: Lysine
What would happen if a “C” was substituted at the third position in this codon?
Practice Problem Questions:
What would happen if an “A” was substituted at the third position in this codon?
Answer: The codon AAA would still call for the amino acid lysine. There would be no effect on the protein being made.
What amino acid would be called for by the codon AAG?
Answer: Lysine
What would happen if a “C” was substituted at the third position in this codon?
Answer: The codon AAC would call for the amino acid asparagine. The protein being made would be altered.
Practice Problem Questions:
What would happen if an “A” was substituted at the third position in this codon?
Answer: The codon AAA would still call for the amino acid lysine. There would be no effect on the protein being made.
There are Two Types of Point Mutations
Base Pair Insertions or Deletions:
A nitrogen base is inserted or removed from the DNA sequence.
What happens when there is a deletion at the second base? How will the ribosome “read” the mRNA?
Insertions and Deletions
1. If a nitrogen base is inserted or removed from the DNA sequence, the code is still read in three-base codons, but now those three-base groupings are shifted for every codon that follows.
2. These mutations have a disastrous effect on the resulting protein.
Insertions and Deletions
3. For example, consider this codon sequence:
If the “G” is deleted in the first codon, the codons would be read as follows:
The codons are still read in groups of three nitrogen bases.
All the nucleotides that are downstream of the deletion or addition will be improperly grouped into codons.
The addition or deletion of a base would alter the reading of the entire rest of the mRNA.
4. These mutations can alter a protein so much that it is unable to perform its normal functions.
AUG AAU GUU UGG UAU UAA
AUA AUG UUU GGU AUU AA
Insertions and Deletions
3. For example, consider this codon sequence:
If the “G” is deleted in the first codon, the codons would be read as follows:
AUG AAU GUU UGG UAU UAA
AUA AUG UUU GGU AUU AA
The codons are still read in groups of three nitrogen bases.
All the nucleotides that are downstream of the deletion or addition will be improperly grouped into codons.
The addition or deletion of a base would alter the reading of the entire rest of the mRNA.
4. These mutations can alter a protein so much that it is unable to perform its normal functions.
Redundancy of the Genetic Code
Nature’s Safety Net!
Which substitution mutation has the
potential to cause more damage and why?
B) The sequence GAU changes in the 3rd base to GAA
C) The sequence GGG changes in the 3rd base to GGC
Which substitution mutation has the
potential to cause more damage and why?
B) The sequence GAU changes in the 3rd base to GAA
GAU-aspartic acid GAA- glutamic acid
C) The sequence GGG changes in the 3rd base to GGC - both code for glycine (Gly)
The Importance of Mutations
1. Most gene mutations are neutral. They have little or no effect.
2. Some mutations cause such dramatic changes that normal cell functions are disrupted and may result in a genetic disorder.
3. Mutations that occurs in the body cells of an organism affect only that organism.
For example, mutations in some body cells may lead to cancer.
Mutations that occur during gamete production can be passed to future offspring and may lead to new variations of phenotypes within a population.
If these mutations create a favorable change in the offspring, the offspring may be better suited for the environment.
Those organisms that are better suited are more likely to survive, reproduce, and pass these favorable traits on to their offspring.
This is the mechanism of Natural Selection
Complete the 3.04 Quiz
GIMKIT Review Game