Download What causes gene mutations?

What is a mutation?
A mutation is a permanent change in the
sequence of DNA.
What causes gene mutations?

Most mutations happen when the cell makes errors as it
copies its genes during interphase. Each time one of your
cells divides, it must copy around 6,000 million letters of
DNA code. Very rarely, mistakes are made, causing
mutations.

Chemicals and radiation can damage genes.
What is a Genetic Disorder?

A genetic disorder is a disease or illness that is caused by
a change, or mutation, in an individual’s DNA sequence.

These changes can affect the individual bases (A, C, G or
T) or much larger chunks of DNA or even chromosomes.

Depending on where these mutations occur, they can have
little or no effect, or may seriously change the biology of
cells in our body, resulting in a genetic disorder.
3 Main Categories of Genetic Disorders

Single gene disorders: disorders caused by defects in just one gene

Dominant diseases: single gene disorders that occur when an individual has one
altered copy of the responsible gene and one healthy copy.


Recessive diseases: single gene disorders that only occur when an individual has two
altered versions of the responsible gene.


muscular dystrophy
Chromosome disorders: disorders due to changes in the number or structure of
the chromosomes.


cystic fibrosis
X-linked disorders: single gene disorders that reflect the presence of an altered gene
on the X chromosome. X-linked disorders are more common in males because they
only have one X chromosome. As a consequence males only need one copy of the
altered gene for symptoms to occur.


Huntington’s disease, albinism
Down’s syndrome - results from an extra chromosome 21 (trisomy 21: three copies of
chromosome 21).
Multifactorial disorders (complex diseases): disorders caused by changes in
multiple genes, often due to environmental and/or lifestyle factors such as
diet, cigarette smoke or radiation.

cancer
http://www.yourgenome.org/facts/what-is-a-genetic-disorder
Types of Mutations

Not all mutations are bad. Some actually help the
organism and some have no affect at all.
 Negative
mutation - will decrease the organism’s chance
of survival. Rare.
 Positive
mutation – will increase the organism’s chance
of survival. Very rare.
 Neutral
mutation - will not affect the organism’s survival
rate. Most common.
Mutation
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Mutations
Mutations
Mutations
Mutations
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