1.6 mutations

Mutations

Mutations are permanent changes to the actual sequence of DNA bases and can lead to the alteration or absence of proteins

Point mutations

Occur to the genetic code of human cells through error in DNA replication

Mostly occur in non-coding DNA and have no effect

When it occurs to coding DNA problems could arise

Results from a single base being substituted inserted or deleted

Base substitutions

Where one nucleotide with a base attached is substituted for a different one

Silent mutation

Occurs when a base substitution results in the altered codon corresponding to the same amino acid

Missense mutations

Occurs when a base substitution results in the altered codon coding for a different amino acid

Nonsense mutation

Occurs when a base substitution results in the altered codon coding for a stop codon instead of an amino acid

Large scale mutations

Invloves large scale changes to the structure or umber of chromosomes in a cell

Occurs during meiosis

Examples:

-          Deletion: genetic material breaks off from a section of the chromosome and is lost

-          Duplication: genetic material is and extra copies of genes are found on the chromosomes

-          Translocation: a section of one chromosome detaches and moves to a new chromosome

-          Inversion: a section of broken chromosome is inserted back but the segment is reversed during the process

-          Insertion: a section of DNA from one chromosome may be removed and added to another chromosome

-          Aneuploidy: chromosome mutation that leads to an abnormal number of chromosomes

Factors that increase the rate of mutation

Mutations occur spontaneously but the natural rate is low

Rates can be increased by physical, chemical, or biological factors (mutagens)\

Physical: high energy radiation

Chemical: chemicals in the environment such as asbestos and cigarette smoke

Biological: viruses

Consequences of mutations

Germline cell can be passed on to future generations

Somatic cells (all cells in the body other than sex cells) mutation can cause serious disease but will not be inherited by future generations