Mutations

A permanent change in a cell’s DNA Rare Some cells have repair mechanisms to fix some damage

Types of Mutations and Resulting Phenotypic Changes Translocations - Translocations are the transfer of a piece of one chromosome to a non-homologous chromosome. They are often reciprocal, with the two chromosomes swapping segments with each other. Translocations Example: Cancer: several forms of cancer are caused by acquired translocations (as opposed to those present from conception); this has been described mainly in leukemialeukemia

Types of Mutations and Resulting Phenotypic Changes Inversion - A region of DNA on the chromosome can flip its orientation with respect to the rest of the chromosome. Inversion Example: Opitz-Kaveggia syndrome (FG Syndrome) X-linked causes mental retardation, short stature, low muscle tone, and respiratory condition…usually males

Types of Mutations and Resulting Phenotypic Changes DeletionsDeletions - A large section of a chromosome can be deleted resulting in the loss of a number of genes. Ex:Cystic fibrosis-characterized by abnormally thick mucus in the lungs, intestines, and pancreas

Types of Mutations and Resulting Phenotypic Changes Duplications - In this mutation, some genes are duplicated and displayed twice on the same chromosome. Duplications Example: Charcot-Marie-Tooth Disease-damage to peripheral nerves leading to weakness and atrophy of muscles in hands and lower legs

Types of Mutations and Resulting Phenotypic Changes Insertion-addition of one or more nucleotide base pairs into a DNA sequencenucleotidebase pairs DNA Example: Crohn’s disease: chronic inflammation of the intestinal tract, leading to diarrhea, nausea, etc.

Types of Mutations Nondisjunction-Failure of chromosomes to separate Example: Down Syndrome

Causes of Mutations Spontaneously Chemicals- change the chemical structure of the bases (mispairing or bond with wrong base) Some chemicals are so similar to the base they can mimic the properties and act as a substitute Radiation- X-rays and gamma rays UV radiation causes adjacent thymine bases to bind together disrupting the DNA sequence and prevents replication – Mutation Video Mutation Video

Explain the relationship between… Mutation, Cell cycle Uncontrolled cell growth Cancer

Cancer is…. An abnormal mass of cells with uncontrolled cell growth. 2 Types Benign- a mass of normal cells growing out of control Malignant- mass of abnormal cells growing out of control

Proto-oncogenes-normal gene that can become an oncogene due to mutations or increased expression. Proto-oncogenes code for proteins that help to regulate cell growth and differentiation. Oncogenes (cancer causing gene)- is a gene that, when mutated or expressed at high levels, helps turn a normal cell into a tumor cell. Many abnormal cells normally undergo a programmed form of death (apoptosis). Activated oncogenes can cause those cells to survive and proliferate instead Tumor-Suppressor Genes- code for proteins that serve as the "stop" signals prohibiting cell cycle from dividing Cancer Video

How do Phenotypic Changes Occur If a mutation occurs in a germ-line cell (one that will give rise to gametes, i.e., egg or sperm cells), then this mutation can be passed to an organism's offspring As opposed to germ-line mutations, somatic mutations occur in cells found elsewhere in an organism's body. Such mutations are passed to daughter cells during the process of mitosis, but they are not passed to offspring conceived via sexual reproduction.