Download Mutations and Genetic Disorders 1. Silent mutation: a base is

Introduction to Mutations
Mutations and Genetic Disorders
Causes of Mutations
1.Mutagens: environmental
factors that can cause some
mutations
2.Examples of mutagens:
a.UV radiation
b.Pollution
c.Certain chemicals
d.Viruses
1.Most genetic disorders result from a
mutation in one gene.
a.Mutation: a change in an organism’s
genetic material (DNA)
2.A mutated gene produces a flawed
protein that does not function properly
or a protein that does not function at
all.
a.Examples of genetic disorders that
are caused by the mutation of one
gene: Hemophilia, sickle cell
anemia, and cystic fibrosis.
Normal
blood cells
Sickleshaped
blood cells
Gene Mutations Caused by Point Mutation
1. Point mutations : one base is replaced
with the wrong base (letter)
2. Also called “Single base substitution”
3. Example: Sickle-cell anemia
UV radiation can cause mutations.
Viruses can cause mutations.
Sickle cell anemia
Point Mutations: Silent Gene Mutations
1. Silent mutation: a base is changed, but
the new codon codes for the same amino
acid. ( typically it is the third letter in the
codon) Not all mutations are harmful.
Original
leading to a silent mutation
mRNA
Protein
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Point Mutations: Missense Mutations
1. Missense Mutations: point mutation
that still codes for an amino acid, just the
wrong amino acid
2. May or may not be harmful
Point Mutations: Nonsense Mutations
1. Nonsense mutations:
prematurely code for a stop codon
2. Result: a nonfunctional protein
Original
Original
Nonsense
mRNA
Protein
mRNA
Protein
Frameshift Mutations: Deletion
Frameshift Mutations: Insertion
1. Deletion: one or more
of the bases is deleted
from the code
1. Insertion: one or more
base pairs are inserted
into the code
2. Causes a shift in the
reading frame
2. Causes a shift in the
reading frame
3. Usually ends up causing
a missense or a
nonsense mutation.
Deletion
Significance of Mutations
Many mutations have little or no effect on the
expression of genes.
Mutations may be harmful and may be the
cause of many genetic disorders and cancer.
Source of genetic variability in a species (may
be highly beneficial).
3. Usually ends up making
a missense or a
nonsense mutation.
Insertion
Beneficial Mutations
Beneficial mutations may produce proteins with
new or altered activities that can be useful to
organisms in different or changing environments.
Plant and animal breeders often take advantage of
such beneficial mutations.
– The condition in which an organism has extra
sets of chromosomes is called polyploidy.
• Often larger and stronger than diploid
plants.
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Gene Regulation
Only a fraction of the genes in a cell are “expressed” at any
given time
(An “expressed” gene = exons= genes that are actually
transcribed into RNA)
 Development and Differentiation
Regulation of gene expression is important in shaping the way
an organism develops, shaping the way cells undergo
differentiation.
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