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POINT MUTATIONS
Not like X-Men
MUTATION
 Any
change in the genetic
sequence (DNA) that
affects the genetic
information
POINT MUTATIONS
 Occurs
 These
at 1 single point in DNA
could cause one amino
acid to change, which would
change the protein that is being
produced.
POINT MUTATIONS

BASE SUBSTITUTION:
– A nucleotide is replaced with a different
nucleotide.
– Three examples:
 Transversion
mutation
 Transition mutation
 Silent mutation
BASE SUBSTITUTION
Examples:

Transversion – happens when one
purine (A,G) is swapped with a
pyrimidine (C,T).
DNA:
mRNA:
AA:
CTT to CAT
GAA to GUA
Glu
to Val
Transversion Substitution
BASE SUBSTITUTION
Examples:

transition mutations – happen
when one purine is swapped with the
other purine or a pyrimidine is
swapped with a pyrimidine.
DNA:
mRNA:
AA:
CTT to CCT
GAA to GGA
Glu
to Gly
BASE SUBSTITUTION
Examples:

Silent mutations – happen when a
base codon is changed but both code
for the same amino acid.
DNA:
mRNA:
AA:
GAA to GAC
CUU to CUG
Leu
to Leu
POINT MUTATIONS

FRAMESHIFT: Because of a point
mutation, there is a shift in the “reading
frame” of genetic message
– Almost always affect all the amino acids
after the mutation, which will affect the
entire protein.
Frameshift Mutation
Examples:

Insertion
– Shifts the reading to the right
– DNA:
from GCATCG to GCC ATC
– mRNA: from CGU AGC to CGG UAG
– Amino
Acid: from Arg Ser to Arg STOP
Point Mutation

Deletion
– Shifts the reading to the left
– DNA:
from GCATCG to GAT CG
– mRNA: from CGU AGC to CUA GC
– Amino
Acid: from Arg Ser to Leu
A New Subtype of Brachydactyly Type B Caused by
Point Mutations in the Bone Morphogenetic Protein
Antagonist NOGGIN
Hutchinson-Gilford progeria syndrome The disease is caused by a small point mutation on a
single gene known as LMNA. Almost all cases are caused by the substitution of only one base pair out
of the approximate 25 000 DNA base pairs that compose the LMNA gene. This gene codes for the
protein lamin A, which is important to determine the shape of a cell’s nucleus. It is vital in providing
support to the nucleus’ inner membrane. The mutation in the LMNA gene causes an abnormal form of
the lamin A protein. That malformed protein makes the inner cell membrane unstable and little by
little damages the nucleus; this makes cells more prone to die prematurely. Researchers are still
trying to figure out how exactly this leads to the phenotypes associated with progeria.
CHROMOSOMAL
MUTATIONS
INVERSION and TRANSLOCATION



Inversion: 2 sections of the
chromosome are reversed
Translocation: 1 part of a
chromosome breaks off and attaches
to another part of a chromosome
Duplication: Part of chromosome is
copied
Examples

ORIGINAL CHROMOSOME:
– ABCDEFG – where the letters are representing
genes on the chromosome.

Inversion – ABGFEDC

Translocation – ABCDXYZ

Duplication – ABBBCDEFG
Inversion
Brenden Adams abnormal growth rate
is due to an inversion in
chromosome-12, a growth gene
defect that skyrocketed his growth
rate.
In Brenden’s case, his
12th chromosomes don’t
match. Experts don’t
know why, but the
middle of one of them
broke off, flipped around
and re-attached at the
zygote stage of
development, disrupting
a critical gene that
controls growth.
http://www.kimatv.com/news/local/11161021.html?tab=video
Translocation Examples

Acute
Promyelocytic
Leukemia –
caused by a
rearrangement
of genetic
material between
chromosome 9
and 22.
Translocation Examples

The section on 15 is responsible for
suppressing tumors (control growth). The
section on 17 is responsible for helping
white blood cells mature. When the two are
translocated, tumors can grow and white
blood cells cannot mature.
It is aquired not inherited.
Translocation
Translocation
A chromosome
5;12
translocation
causes severe
skeletal and
composite
cardiac
malformations.
Duplication
Deletion

a portion of one chromosome is lost
during cell division. That chromosome
is now missing certain genes. When
this chromosome is passed on to
offspring the result is usually lethal
due to missing genes.
Chromosome New Chromosome
Mutation
AbcdEFghijklm Abcdkjlm
1
AbcdEFghijklm AbihgFEdcjklm
2
AbcdEFghijklm AcdEFghijklm
3
AbcdEFghijklm AbcdEFghiWxYz
4
AbcdEFghijklm AbcdbcdEFghijklm
5
AbcdEFghijklm AbcdEFkjihglm
6
AbcdEFghijklm AbcdEFdEFghijklm
7
AbcdEFghijklm Abcdmlkjhg
8
Chromosome New Chromosome
AbcdEFghijklm Abcdkjlm
Mutation
AbcdEFghijklm AbihgFEdcjklm
1 Deletion &
Inversion
2 Inversion
AbcdEFghijklm AcdEFghijklm
3 Deletion
AbcdEFghijklm AbcdEFghiWxYz
4 Translocation
AbcdEFghijklm AbcdbcdEFghijklm
5 Duplication
AbcdEFghijklm AbcdEFkjihglm
6 Inversion
AbcdEFghijklm AbcdEFdEFghijklm
7 Duplication
AbcdEFghijklm Abcdmlkjhg
8 Deletion &
http://www.chemistryexplained.com/MaNa/Mutation.html
http://embryology.med.unsw.edu.au/Defect/p
age21.htm
http://www.biology.arizona.edu/human_bio/ac
tivities/karyotyping/karyotyping.html
http://www.docstoc.com/docs/38810096/Muta
tions