1. What is a mutation? A mutation is a permanent change in the sequence of DNA.

2. What causes gene mutations?  Most mutations happen when the cell makes errors as it copies its genes. 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.

3. 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.

4. 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.  Huntington’s disease, albinism  Recessive diseases: single gene disorders that only occur when an individual has two altered versions of the responsible gene.  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.  muscular dystrophy  Chromosome disorders: disorders due to changes in the number or structure of the chromosomes.  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 or cigarette smoke.  cancer http://www.yourgenome.org/facts/what-is-a-genetic-disorder

5. Some Genetic Disorders

6. 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.

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