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GENETIC DISORDERS

GENETIC DISORDERS. 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 !. SINGLE-GENE DEFECTS.

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GENETIC DISORDERS

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  1. GENETIC DISORDERS

  2. Mutation –change in a gene resulting in change in genetic information • may be spontaneousor 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 10 000 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. X Y O XX SEX CHROMOSOME NONDISJUNCTION DISORDERS XY XX

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