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KARYOTYPE AND GENETIC DISORDERS

KARYOTYPE AND GENETIC DISORDERS. H. Biology. Chromosomes Determine Your Gender. Humans have 23 pairs of chromosomes 22 pairs are autosomes (chromosomes that are NOT involved in making gender) Also called homologous chromosome pairs

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KARYOTYPE AND GENETIC DISORDERS

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  1. KARYOTYPE AND GENETIC DISORDERS H. Biology

  2. Chromosomes Determine Your Gender • Humans have 23 pairs of chromosomes • 22 pairs are autosomes(chromosomes that are NOT involved in making gender) • Also called homologous chromosome pairs • 1 pair are sex chromosomes (NOT HOMOLOGOUS; different genes) • The sex chromosomes are “X” and “Y” • “XX” is a girl • “XY” is a boy X Egg cells ALWAYS have “X” chromosome Y X Y

  3. Pair of homologous chromosomes 5 µm Centromere Sister chromatids A karyotype • an ordered, visual representation of ALL chromosomes in a human cell • Arranged according to homologous pairs

  4. a REAL view…wow!!!

  5. What is a genetic disorder? What causes a genetic disorder? • Caused by an abnormality in an individual’s DNA How do these abnormalities occur? • Non-disjunction • Addition or subtraction of chromosome or set of chromosomes • Mutations • Change to DNA sequence (gene)

  6. Abnormal Chromosome Number • When nondisjunctionoccurs • Pairs of homologous chromosomes do NOT separate normally during meiosis • Gametes contain 2 copies or NO copies of a particular chromosome • What are some disorders caused by non-disjunction? • Downs Syndrome • Trisomy 21 • Klinefelter’s Syndrome • XXY • Turner Syndrome • Monosomy X

  7. What happens when meiosis goes wrong? NONDISJUNCTION!!!

  8. Meiosis I Nondisjunction Meiosis II Nondisjunction Gametes n 1 n + 1 n + 1 n –1 n + 1 n – 1 n n Number of chromosomes (a) (b) Nondisjunction of homologous chromosomes in meiosis I Nondisjunction of sister chromatids in meiosis II Figure 15.12a, b

  9. Aneuploidy • Results from the fertilization of gametes in which nondisjunction occurred • Offspring have an abnormal number of a particular chromosome

  10. What are some disorders caused by non-disjunction? • Downs Syndrome • Trisomy 21 • Kleinfelter’s Syndrome • XXY • Edwards Syndrome • Trisomy 18 • Patau Syndrome • Trisomy 13 • Turner Syndrome • Monosomy X

  11. 1.) Trisomy 18-Edwards Syndrome

  12. 2.) Trisomy-13: Usually Fatal

  13. 3.) Klinefelter - XXY

  14. Klinefelter syndrome • a result of an extra chromosome in a male, producing XXY individuals • 1/2000 live births

  15. XYY individuals

  16. Triple X Syndrome XXX individuals • Females • Healthy • Same phenotype as XX individuals • 1/1000 live births

  17. 4.) Turner Syndrome

  18. Turner syndrome • Is the result of monosomy X, producing an X0 karyotype • 1/5000 live births • Only known monosomy in humans • Normal intelligence • Sterile

  19. 5.)Trisomy 21

  20. Human Disorders Due to Chromosomal Alterations • Down syndrome • Is usually the result of an extra chromosome 21 • trisomy 21

  21. What are some disorders caused by mutations? • Sickle cell anemia (recessive) • Cystic fibrosis (recessive) • Maple syrup urine disorder (recessive) • Congenital hypothyroidism (recessive) • Huntington’s Disease (dominant)

  22. Cystic Fibrosis • Example of recessive disorder • Affect mostly people of European descent • Symptoms • Mucus buildup in the some internal organs • Abnormal absorption of nutrients in the small intestine

  23. Sickle Cell Anemia • Another recessive disorder • Affects one out of 400 African-Americans • Hemoglobin is the O2 carrying protein in red blood cells • SCA is an inherited blood disease where hemoglobin clumps together  • causes red blood cells to stiffen and curl into a sickle/crescent shape • Because of this, the RBC cannot transport O2 effectively • Symptoms • Physical weakness, pain, organ damage, and even paralysis

  24. Human Chromosomal Disorders Recessive Disorders • Cystic Fibrosis • Excess mucus in lungs, digestive tract, liver • More susceptible to pneumonia, infection • Early death ~ average age of 37 • Tay-Sachs • Lipid accumulation in brain cells, mental retardation • Blindness, death in childhood Dominant Disorder • Huntington’s disease • Deterioration of nervous system, uncontrollable movements • Develops in middle age, death soon after

  25. Dominantly Inherited Disorders • Some human disorders • Are due to dominant alleles  only need 1 dominant allele • Example is achondroplasia • Form of dwarfismlethal when homozygous for the dominant allele

  26. Another Dominant Disorder • Huntington’s disease (HD) • degenerative disease of nervous system • No obvious phenotypic effects until about 35 to 40 years of age HD Normal

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