Chapter 12 Section 4
Mutations
Mutations
•
•
•
DNA contains the code
of instructions for cells.
Sometimes, an error
occurs when the code
is copied.
- Such errors are called
mutations.
Mutations are
changes in the genetic
material.
2 Types of Mutation
•
2 types:
1. Gene mutation
produce changes in a
single gene
2. Chromosomal
mutation produce
changes in whole
chromosomes
Gene Mutations
•
•
Point mutation gene mutations involving
changes in 1 or a few nucleotides
- Occurs at a single point in the DNA sequence
Includes:
a. Substitutions 1 base changed to another
b. Insertions a base is inserted or added
c. Deletions a base is deleted or removed
Cont. Gene Mutations
Deletion
Substitution
Insertion
• Substitutions usually affect no more than a single amino acid
• The effects of insertions/ deletions can be much more dramatic.
Cont. Gene Mutations
• Frameshift mutations a
change that shifts the
“reading frame” of the
genetic message (caused
insertion/ deletion)
- By shifting the reading
frame, frameshift mutations
may change every amino
acid that follows the point of
mutation.
- Can alter a protein so
much that it is unable to
perform its normal function
Gene Mutation
Picture of “Mighty Belgium Blue” cattle
- Alter in myostatin gene
- Produces meatier cattle/ 20% more meat per animal
on roughly the same food intake as ordinary animals
Chromosomal Mutations
• Changes in the number or structure of chromosomes
a. Deletions involves loss of all or part of a chromosome
b. Duplication produce extra copies of parts of a chromosome
c. Inversions reverse the direction of parts of a chromosome
d. Translocation when part of a chromosome breaks off & attaches to another
Significance of Mutations
a)
b)
Harmful mutations
- Produce defective proteins that disrupt normal
biological activities
- Causes genetic disorders
- Associated with many cancers
Beneficial mutations
- Produce proteins w/ new/ altered activities that can
be useful to organisms in different/ changing env
- Source of genetic variability in species
- Polyploidy an organism w/ extra sets of
chromosomes
Ex: polyploid plants are often larger & stronger
then diploid plants (bananas & many citrus fruits)
Polyploid