2. In biology, a mutation is the alteration of
the nucleotide sequence of the genome of
an organism, virus, or extrachromosomal DNA.
Mutations result from errors during DNA replication
or other types of damage to DNA, such as may be
caused by exposure to radiation or carcinogens, or
cause an error during other forms of repair…
3.
4.
5.
6. Good vs. Bad Mutations
A good mutation could lead to a change in a protein
that allows an animal to run faster or see better.
A bad mutation could lead to a change in a protein
that causes a genetic disease such as Sickle Cell Anemia
or Hemophilia.
7.
8. Advantages
• In 2008, Professor Eiberg from the
Department of Cellular and Molecular
Biology stated, “Originally, we all had brown
eyes but a genetic mutation affecting the
OCA2 gene in our chromosomes resulted in
the creation of a ,,switch,” which literally
,,turned off” the ability to produce brown
eyes.” He explains that things like “hair color,
baldness, freckles, and beauty spots” are all
brought about by mutations.
9. Advantages
• Mutations have allowed humans to adapt to
their environment.
• For instance, lactose tolerance is a specific
external mutation that was advantageous in
societies that raised cows and goats.
• Mutations have been responsible for
antibiotic resistance in bacteria, sickle cell
resistance to malaria, and immunity to HIV,
among others.
•
10. Disadvantage - Disease
• As much as mutations have helped humans,
mutations are also the cause of certain diseases.
• For instance, Science News explains how a
particular mutation relatively common on the
Indian subcontinent predisposes people to heart
disease.
• Many other diseases, such as cancer, diabetes
and asthma, are linked to genetic mutations.
11. Disadvantage - Genetic Disorder
• A genetic disorder is a disease that is caused by
an abnormality in an individual's DNA.
Abnormalities can range from a small mutation
in a single gene to the addition or subtraction of
an entire chromosome or set of chromosomes.
• Non-disjunction is one of the most common
types of mutations.
• Down syndrome is a non-disjunction and a
common genetic disorder that has other
consequences such as developmental delays.
12.
13.
14.
15. Gene Mutations
• There are 2 main types of
gene mutations:
• 1. POINT MUTATIONS
• SUBSTITUTIONS
Nonsense
Missense
Silent
• 2. FRAMESHIFT MUTATIONS
Insertion
Deletion
16. A point mutation
• Type of mutation in DNA or RNA, the cell’s genetic
material, in which one single nucleotide base is
added, deleted or changed.
• There are two types of point mutations: transition
mutations and transversion mutations.
• Transition mutations occur when a pyrimidine base
substitutes for another pyrimidine base or when
a purine base substitutes for another purine base.
• In double-stranded DNA each of the bases pairs with
a specific partner on the corresponding strand .
• In contrast, transversion mutations occur when a
purine base substitutes for a pyrimidine base, or vice
versa;
17. Point mutation
Point mutation- a change in one base pair in a DNA
sequence.
Example: AUG=Met
AAG=Lys
-A point mutation can cause an amino acid to
change, which will change the structure of the
protein being made.
19. Types of Point Mutations
Substitution
• A substitution mutation occurs when
one base pair is substituted for another.
• Nonsense
• Missense
• Silent
• A nonsense mutation occurs when one
nucleotide is substituted and this leads to the
formation of a stop codon instead of a codon
that codes for an amino acid.
20. • Like a nonsense mutation, a missense mutation occurs when
one nucleotide is substituted and a different codon is
formed; but this time, the codon that forms is not a stop
codon. Instead, the codon produces a different amino acid in
the sequence of amino acids.
• For example, if a missense substitution changes a codon
from AAG to AGG, the amino acid arginine will be
produced instead of lysine.
• A missense mutation is considered conservative if the
amino acid formed via the mutation has similar
properties to the one that was supposed to be formed
instead.
• It is called non-conservative if the amino acid has
different properties that structure and function of a
protein.
21. In a silent mutation, a nucleotide is substituted but the same amino acid is
produced anyway. This can occur because multiple codons can code for the
same amino acid. For example, AAG and AAA both code for lysine, so if the
G is changed to an A, the same amino acid will form and the protein will not
be affected.
image shows the DNA codon/resulting RNA codon/amino acid produced.
22. Point mutations in our lives!
-Sickle cell anemia is a blood disease caused by a
point mutation.
-A single nucleotide is changed from “A” to “T” which
causes the amino acid to change from glutamic acid to
valine:
Normal: ACT CCT GAG GAG
Amino Acids: Thr – Pro – Glu – Glu
Sickle cell: ACT CCT GTG GAG
Amino acids:Thr – Pro – Val – Glu
23. Point mutations in our lives!
-People with sickle cell
anemia often
experience a lot of
pain and swelling and
have trouble
exercising.
Sickle cells also can’t carry
Oxygen as effectively as normal
Cells.
24. Insertion and Deletion- frameshift mutation.
• An insertion mutation occurs when an extra
base pair is added to a sequence of bases.
• A deletion mutation - occurs when a base
pair is deleted from a sequence.
• These two types of mutations are grouped
together because both of them can
drastically affect the sequence of amino acids
produced.
• With one or two bases added or deleted, all
of the three-base codons change. This is
called a frameshift mutation.
25. A frameshift mutation is much worse than a point
mutation because it causes the entire DNA
sequence to be shifted over!
Example: DNA: ATTAAACCG
ATAAACCG
Frameshift mutation
Delete this T
26. 2 types of Frameshift mutations:
Insertion: Nucleotide added –
Entire DNA sequence changed
Deletion: Nucleotide missing –
Entire DNA sequence changed
27. In this example, the original reading frame of a gene encodes an mRNA with
codons that specify the amino acid sequence: methionine (Met), isoleucine
(Ile), argenine (Arg), and asparagine (Asn).
A deletion of the 4th nucleotide (T) produces a new reading frame in the
DNA template after the 3rd nucleotide. The mRNA of the new frame bears
different codons: the first methionine-specifying codon remains
unchanged):methionine (Met), tyrosine (Tyr), and glycine (Gly).
As this example illustrates, a frameshift mutation may change the amino
acid sequence.
28. Frameshift Mutations
• Crohn’s Disease is caused by a frameshift mutation.
• Crohn's disease is a type of inflammatory
bowel disease (IBD) that may affect any part of the
gastrointestinal tract from mouth to anus. Signs and
symptoms often include abdominal pain, diarrhea (which
may be bloody if inflammation is severe), fever, and weight
loss.
29. Questions:
Is this a point mutation or a
frameshift mutation?
It’s a point mutation because only one nucleotide
changed!
33. In multicellular organisms, mutations can be
classed as either somatic or germ-line:
• Somatic mutations – occur in a single body cell
and cannot be inherited.
• Germline mutations – occur in gametes and
can be passed onto offspring .
34.
35.
36.
37.
38. Chromosome Mutation
A chromosome mutation is an unpredictable
change that occurs in a chromosome.
These changes are most often brought on by
problems that occur during meiosis or by
mutagens (chemicals, radiation, etc.).
Chromosome mutations can result in changes in
the number of chromosomes in a cell or changes
in the structure of a chromosome.
Unlike a gene mutation which alters a single
gene or larger segment of DNA on a chromosome,
chromosome mutations change and impact the
entire chromosome.
39. Aneuploidy: Extra or missing chromosomes
• most of your cells contain 46 chromosomes, rod-like
structures made of DNA and protein, that come in 23
perfectly matched pairs.
• In organisms with two full chromosomes sets, such as
humans, this number is given the name 2n.
• When an organism or cell contains 2n chromosomes, it is
said to be euploid, meaning that it contains chromosomes
correctly organized into complete sets (eu- = good).
• If a cell is missing one or more chromosomes, it is said to
be aneuploid (an- = not, "not good").
• For instance, human somatic cells with chromosome
numbers of (2n-1) = 45
40. Two common types of aneuploidy have
their own special names:
• Monosomy is when an organism has only one
copy of a chromosome that should be
present in two copies (2n-1)
• Trisomy is when an organism has a third copy
of a chromosome that should be present in
two copies (2n+1)
41.
42. polyploid.
• Aneuploidy also includes cases where a cell
has larger numbers of extra or missing
chromosomes, as in (2n - 2), (2n + 3)
(2n−2),(2n+3) etc.
• However, if there is an entire extra or missing
chromosome set (e.g., 3n), this is not
formally considered to be aneuploidy, even
though it may still be bad for the cell or
organism.
• Organisms with more than two complete sets
of chromosomes are said to be polyploid.
43. Chromosomal rearrangements
• In another class of large-scale mutations, big chunks of
chromosomes are affected.
• Such changes are called chromosomal rearrangements.
They include:
• A duplication, where part of a chromosome is copied.
• A deletion, where part of a chromosome is removed.
• An inversion, where chromosomal region is flipped
around so that it points in the opposite direction.
• A translocation, where a piece of one chromosome gets
attached to another chromosome.
44. part of a chromosome is removed copied region is flipped around so that it points
in the opposite direction.
45. A translocation, where a piece of one chromosome gets
attached to another chromosome:
A reciprocal translocation involves two chromosomes
swapping segments;
a non-reciprocal translocation means that a chunk of one
chromosome moves to another
46. In some cases, a chromosomal rearrangement causes
symptoms similar to the loss or gain of an entire
chromosome.
For instance, Down syndrome is usually caused by a
third copy of chromosome 21, but it can also occur
when a large piece of chromosome 21 moves to
another chromosome (and is passed on to offspring
along with a regular chromosome 21)
In other cases, rearrangements cause unique
disorders, ones that are not associated with
aneuploidy.
47.
48. quick summary of a few of these:
• Substitutions
• A substitution changes a single base
pair by replacing one base for another.
• Silent mutations do not affect the
sequence of amino acids during
translation.
• Nonsense mutations result in a stop
codon where an amino acid should be,
causing translation to stop
prematurely.
• Missense mutations change the amino
acid specified by a codon.
51. Frameshift
• Because the genetic
code is read in codons
(three bases at a time),
inserting or deleting
bases may change the
"reading frame" of the
sequence. These types
of mutations are
called frameshift
mutations.
