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GENETIC DISORDERS. Mutation –change in a gene resulting in change in genetic information may be spontaneous or caused by a mutagen Somatic mutations are.

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Presentation on theme: "GENETIC DISORDERS. Mutation –change in a gene resulting in change in genetic information may be spontaneous or caused by a mutagen Somatic mutations are."— Presentation transcript:

1 GENETIC DISORDERS

2 Mutation –change in a gene resulting in change in genetic information may be spontaneous or caused by a mutagen Somatic mutations are usually not noticed Gametic mutations are more severe Not all mutations are bad!

3 SINGLE-GENE DEFECTS Misplacement, insertion or deletion of one base pair May result in incorrect amino acid May result in shift of reading frame Congenital Defects: – Visible at birth(club foot, spina bifida, congenital heart defects) – Caused by environmental factors (FAS, German measles) Inherited – Sickle Cell Anemia, Cystic Fibrosis

4 INVERSIONS Part of chromosome is flipped around 180° from its normal orientation. Happens when chromosome breaks occur. Broken piece may reattach, but not necessarily in the same orientation as before

5 TRANSLOCATIONS Detachment of a segment of a chromosome, and reattachment to another non-homologous chromosome. Some genes wind up on a completely different chromosome

6 ANOMALIES OF CHROMOSOME NUMBER Polyploidy is common in plants Gametes don’t reduce chromosome # Result in cells with multiple copies of the genome

7 ANOMALIES OF CHROMOSOME NUMBER Aneuploidy – more common in humans Usually lethal before or shortly after birth Monosomic and Trisomic

8 NONDISJUNCTION Occurs when homologous chromosomes fail to separate after synapsis Most nondisjunction events are lethal to the fetus

9 DOWNS SYNDROME Results from a third copy of chromosome 21 Called a trisomy Individuals have 47 chromosomes in every body cell

10 SEX CHROMOSOME NONDISJUNCTION DISORDERS TURNER SYNDROME Occurs when nondisjunction causes a gamete to have a missing sex chromosome (X O) Sterile females 1 in live births

11 SEX CHROMOSOME NONDISJUNCTION DISORDERS KLINEFELTER’S SYNDROME Genotype of XXY (extra sex chromosome) Sterile males, breast development 1 in 800 live births

12 SEX CHROMOSOME NONDISJUNCTION DISORDERS ½ ½ ½ gamete lacking a sex chromosome XO ¼ Turner’s syndrome YO ¼ Will not survive (LETHAL CONDITION) ½ gamete formed from nondisjunction XXX ¼ “super female” usually normal XXY ¼ Klinefelter’s syndrome XY XY O XX


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