1. Mutations And their effects

2. A mutation is…  A permanent change that occurs in a cell’s DNA.

3. Point Mutation:  Is a chemical change in just one base pair.  Can cause a genetic disorder.  There are several types of point mutations.

4. Types of Point Mutations  Substitutions  Missense  Nonsense  Frameshifts  Deletion  Insertion  Duplication  Expanding Mutation (Tandem Repeats

5. Substitutions- when one base is exchanged for another.  Missense:  When the DNA code is altered and codes for the wrong amino acid.  Example: Achondroplasia  Nonsense:  Cause translation (making of a protein) to terminate early.  Example: Muscular Dystrophy

6. Frameshift Mutations- changes the multiples of three codons from the point of insertion or deletion.  Deletions:  The deletion of nucleotides to the DNA sequence.  Example: Cystic Fibrosis  Insertions:  The addition of nucleotides to the DNA sequence.  Example: Crohn’s Disease

7. Expanding Mutation- Tandem Repeats  Is an increase in the number of copies of repeated codons.  Can cause a number of genetic disorders:  Examples: Fragile X Syndrome and Huntingtons Disease

8. Causes of Mutations:  Can occur spontaneously  Can be caused by radiation:  X-rays and gamma rays are highly mutagenic, Ultraviolet radia tion  Can be caused by mutagens  Mutagens are chemicals that can change the chemical structure of nucleotide bases.

9. Somatic Cell vs. Gamete Mutation  Somatic Cell Mutations:  Once past repair are passed on to daughter cells, but is NOT passed on to future generations of children.  Sometimes don’t cause any problems  Can result in production of abnormal protein, which can cause cell death.  Can lead to cancer if regulation of cell cycle is affected by mutation.

10. Somatic Cell vs. Gamete Mutation  Gamete Mutations:  Passed on to offspring and will be present in every cell of the offspring.  If mutation causes production of an abnormal protein in a gamete the consequences are far worse than if an abnormal protein is produced in an isolated body cell.

11. Nondisjunction  When sister chromatids fail to separate properly during meiosis. Can occur in both autosomes and sex chromosomes.  Results in the gametes having an incorrect number of chromosomes.  Can result in the gamete having EXTRA copies of chromosomes or only ONE copy of a chromosome.  Trisomy-having a set of 3 chromosomes of one kind (Trisomy 21, Trisomy 18, Klinefelters)  Monosomy-having only one copy of a chromosome. (Turners Syndrome)

12. Beneficial Mutations  Can lead to adaptations that help an organism to become better suited to their environment and therefore increase its chances for survival.  Examples include:  Antibiotic resistant bacteria-bacteria have had mutations that make them resistant to antibiotics (beneficial for bacteria, not so much for the organism they invade)  Lactose tolerance in humans is why adults are able to digest milk.