Download Mutations - Fall River Public Schools

Mutations
Not this kind!
Objectives
• Explain what a mutation is
• Compare and contrast gene mutations and
chromosomes mutations
What Are Mutations?
• Cells can sometimes make mistakes when they
copy their own DNA
• These mistakes can include inserting an incorrect
base or skipping a base
• Mutations are changes in genetic material
– A mutation is a change in a DNA sequence that
affects genetic information
• There are two types of mutations:
– Gene Mutations
– Chromosomal Mutations
• Mutations may not affect an organism or they can
be fatal
Gene Mutations
• Gene mutations produce
changes in a single gene
• Point mutations are
changes in one or a few
nucleotides
– Point mutations occur at a
single point in the DNA
sequence
• 3 Types of Point
Mutations
– Substitutions
– Insertions
– Deletions
Substitutions
• One base is changed to another
• Usually affect no more than a single amino acid
Insertions and Deletions
• A base is inserted or removed from the DNA
sequence
• Insertions and Deletions can have more dramatic
effects than substitutions
• Because bases are read in groups of 3, if a
nucleotide is added or deleted, the groupings are
shifted for every codon that follows
– These are known as frameshift mutations
• Frameshift Mutations are mutations that shift
the “reading” frame of the genetic message by
inserting or deleting a nucleotide
Insertion
Chromosomal Mutations
• Involve changes in the number or structure of
chromosomes
– These changes can include changing the locations of
genes on chromosomes and may change the
number of copies of some genes
• There are 4 Types of Chromosomal Mutations:
–
–
–
–
Deletions
Duplications
Inversions
Translocations
Chromosomal Mutations
• Deletions – involve the loss
of all or part of a chromosome
• Duplications – produce extra
copies of parts of a
chromosome
• Inversions – reverse the
direction of parts of
chromosomes
• Translocations – occur when
part of one chromosome
breaks off and attaches to
another
Significance of Mutations
• Most mutations are neutral, meaning that they have little
or no effect
• Mutations that cause dramatic changes in protein
structure or gene activity can disrupt biological process
and can result in genetic disorders
• Some mutations are beneficial and produce proteins
with new or altered activities that can be useful in
different or changing environments
• Mutations in cells that produce gametes can be passed
along to offspring and result in new genetic variation
• Polyploidy – a condition in which an organism has an
extra set of chromosomes
– Polyploidy plants are often stronger and larger than normal diploid
plants
Review
• What is a mutation?
– A mutation is a change in genetic material.
• Contrast gene mutations and chromosomal
mutations.
– Gene mutations produce changes in a single gene.
– Chromosomal mutations produce changes in whole
chromosomes.