Transcript Mutations - Broken Arrow Public Schools

Mutations
•
A mutation is a permanent
change in the DNA or RNA
sequence of a gene.
• There are two ways in which
DNA can become mutated:
1. Mutations can be inherited.
2. Mutations can be acquired.
Kinds of Mutations
Gene mutations & Chromosomal
mutations
Gene Mutations
Point Mutation
This is a single change in one of the
four nucleotide bases. An" A " might
change to a" C " for example.
Mutations that produce
changes in a single gene.
Point Mutation
• A mutation that changes only
one small area or one
nucleotide in a gene.
• Point mutations include
substitution , in which one
base is changed to another, as
well as insertions and
deletions, in which a base is
inserted or removed from the
DNA sequence.
Substitutions
Substitution , in which one base
is changed to another
• swapping an A for a T in a
gene for hemoglobin causes
a serious disease called
sickle cell anemia.
Hemoglobin does the job of
carrying oxygen around
the body in the blood. In
people with sickle cell
anemia, the sequence of
amino acids in hemoglobin
is different, and so it
doesn't work as well.
Deletions
Deletion
Part of the DNA sequence
is missing.
• Part of the DNA sequence —
anywhere from one
nucleotide to a large section
of DNA — is missing.
Deletions can cause the cell
to use the wrong amino acids
to build the protein.
Deletions can also shorten
the protein. In some cases, a
chunk of the protein will be
left out. (Imagine leaving out
the sugar in a cake recipe.)
Many cases of muscular
dystrophy are caused by
deletions.
Insertion
Insertion
Extra nucleotides are added to
the sequence.
• Extra DNA is added to the
normal DNA sequence.
Similar to deletions,
addition of DNA sequence
can cause the cell to use the
wrong amino acids to build
the protein or shorten the
protein. In some cases, the
protein will have extra
amino acids, which could
affect protein function. (Try
to bake a loaf of bread by
adding an improper
ingredient, such as liver.)
Frameshift mutation
• In a frameshift
mutation there
may be an
insertion or
deletion of
several base pairs
causing a
misreading of the
mRNA during
translation.
Chromosomal Mutations
Chromosomes may break during replication, and parts of chromosomes may
then rejoin incorrectly. Letters on the colored chromosomes distinguish
segments and identify consequences of duplications, deletions, inversions,
and translocations.
Mutagens
• An agent, such as a
chemical, ultraviolet
light, or a radioactive
element, that can
induce or increase the
frequency of mutation
in an organism.