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MUTATIONS
Mistakes in DNA
The Big Picture
Chromosome
DNA
double
helix
Coils
Supercoils
Proteins
•Chromosomes are made up of super coiled strands of DNA
•Genes are
•sections of your chromosome
•made up of DNA
Mutations
•
•
Mutations are changes in genetic
material.
There are two major mistakes that can
happen:
1. Chromosomal Mutations
2. Gene Mutations
Type 1: Chromosomal Mutations
• Whole chromosome is affected.
• Large sections of DNA can be
–
–
–
–
Removed from a chromosome
Added to a chromosome
Rearranged within a chromosome
Switched with DNA from another chromosome.
• These mutations are usually very harmful
Chromosomal Mutations
Deletion
loss of material
Duplication
addition of material
Inversion
rearrangement of
material
Translocation
switching material
with another
chromosome
Type 2: Gene Mutations
• Changes that occur in a single gene.
• Change occurs at the DNA nucleotide
level
Nucleotide
Hydrogen
bonds
Sugarphosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Two Types of Gene Mutations
1. Point mutations: one nucleotide that
affects one amino acid.
Example: Substitution
C changes to G
Two Types of Gene Mutations
2. Frameshift mutations:
•
•
involve the reading of the DNA or m-RNA
strand
many amino acids are affected.
Examples:
Insertion
Deletion
Mutation Can Be…
1. Neutral (a.k.a. Silent)
•
Example: Substitution
•
UCU = Serine if the last U is changed to C, A or G the mRNA will
still make Serine
2. Harmful
•
Example: Substitution
•
Sickle Cell Anemia
•
There is a change 17th nucleotide in the code for
hemoglobin
•
A is changed to a T - GAG changes to GTG
•
How does this change the amino acid?
•
GLU changes to VAL
•
This changes hemoglobin’s shape from round to sickle
shaped
Mutation Can Be…
3. Harmful (more harmful)
•
Example: Frameshift - Deletion
•
Shifts the whole reading frame
•
Changes the amino acids produced
4. Harmful (even more harmful!)
•
Example: Chronic myelogenous leukemia
•
Translocation
•
Pieces of 2 chromosomes switch
•
Causes white blood cells to
divide and reproduce improperly.