Presentation on theme: "Genetic Disorders A disease caused by a different form of a gene called a variation, or an alteration of a gene called a mutation."— Presentation transcript:
Genetic Disorders A disease caused by a different form of a gene called a variation, or an alteration of a gene called a mutation.
How genetic disorders occur 1.Monogenetic disorder – mutation of a single gene Is inherited Examples sickle cell anemia
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
3.Chromosomal disorders Alteration of chromosome number Example – Downs Syndrome – extra chromosome
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.
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
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.
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
Monosomy XYY – males taller than normal XXX – females indistinguishable from XX females Turners syndrome – monosomy X – Only know viable monosomy in humans
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.