1. Genetic Disorders A disease caused by a different form of a gene called a variation, or an alteration of a gene called a mutation.

2. How genetic disorders occur 1.Monogenetic disorder – mutation of a single gene Is inherited Examples sickle cell anemia

3. 2.Multifactorial inheritance disorders Caused by a combination of small inherited variations in genes, often acting together with environmental factors. Examples - Heart disease, diabetes, and most cancers

4. 3.Chromosomal disorders Alteration of chromosome number Example – Downs Syndrome – extra chromosome

5. Alteration of chromosome number Diagnosed with Karyotype – fetal cells must be harvested and cultured in vitro. – The chromosomes are removed and arranged in pairs and photographed. – Abnormalities in chromosome number, shape, or size can be detected this way.

6. Causes Nondisjunction one gamete receives two of the same type of chromosome, and another gamete receives no copy. – Problems with the meiotic spindle cause errors in daughter cells – Tetrad chromosomes do not separate properly during meiosis I – sister chromatids may fail to separate during meiosis II

7. Offspring from nondisjunction Have abnormal chromosome number - aneuploidy. – Trisomic cells have three copies of a particular chromosome type and have 2n + 1 total chromosomes. – Monosomic cells have only one copy of a particular chromosome type and have 2n - 1 chromosomes.

8. Examples of aneupoidy Trisomy Downs syndrome –trisomy 21 (3 copies of chromosome 13) Patu syndrome – trisomy 13 – Very short life span – less than 1 year Edwards syndrome – trisomy 1 – Life span less than 10 weeks Kleinfelters syndrome XXY – Normal intelligence – abnormal sex organs

9. Monosomy XYY – males taller than normal XXX – females indistinguishable from XX females Turners syndrome – monosomy X – Only know viable monosomy in humans

10. Task Karyotyping activity at Bio Project http://www.biology.arizona.edu/human_bio/activities/karyotyping/Karyotyping.ht ml http://www.biology.arizona.edu/human_bio/activities/karyotyping/Karyotyping.ht ml 1.Evaluate 3 patients' case histories, 2.Complete their karyotypes, and 3.Diagnose any missing or extra chromosomes 4.Do an internet search to explain your diagnoses.