Human Genetics

1. Human Genetics

2. Genetic abnormality = a genetic condition that is a deviation from the average: not life-threatening Genetic disorder = describes conditions that cause medical problems Human Genetic Disorders

3. Karyotype • A pictorial display of metaphase chromosomes from a mitotic cell • Chromosomes are identified and arranged by their characteristic size, shape, centromere location and staining patterns

4. Human Karyotype

5. Amnio-centesis Detects some fetal abnormalities through karyotyping

6. Human Chromosome Characteristics • Diploid set for humans = 46 • Autosomes= 22 • Female-sex chromosomes = homologous (XX) • Male-sex chromosomes = non-homologous (XY)

7. Either parent can carry the recessive allele on an autosome. Heterozygotes are symptom- free. Homozygotes are affected. Autosomal Recessive

8. One defective or absent gene can result in the inability to make a specific enzyme Recombinant DNA techniques may someday correct faulty chromosomes Genetic Errors of Metabolism Obesity gene discovered

9. Galactosemia Inability to metabolize lactose Cystic Fibrosis Inability to breakdown mucous in lungs and other organs Genetic Errors of Metabolism

10. Missing an enzyme to break down lipids, leading to destruction of central nervous sys. Mainly found in Eastern European Jewish decendents 1:27 is a carrier Judaism is trying to eliminate gene through non-breeding between couples who are carriers Tay-Sachs Disease

11. Recessive, changes the shape of the hemoglobin molecule Extremely painful, debilitating Only distorts when deoxygenated Sickle-cell Anemia

12. High frequency in black populations SS= no sickle-cell Ss = mild symptom ss = full blown disease Sickle-cell Anemia

13. Heterozygote Superiority Heterozygotes receive protection from symptoms of sickle-cell AND malaria - advantage in malarial countries SS + malaria = malaria only Ss + malaria = no symptoms of either ss + malaria = mild sickle cell

14. Sickle cells become trapped and destroyed in the spleen causing SplenicSequestion Anemia Pain episodes Stroke or Brain Damage Kidney failure Pneumonia Increased Infections Complications

15. Lack one enzyme to break down phenylalanine Products accumulate, cause mental retardation, other severe symptoms Treated through dietary restrictions PKU

16. A dominant allele is always expressed and if it reduces the chance of surviving or reproducing, its frequency should decrease Mutations and conditions that set in late in life work against this Autosomal Dominant

17. Achondroplasia (Dwarfism) Lacks functional gene for somatropic hormone in the pituitary Autosomal Dominant

18. Acromegaly (Gigantism) Pituitary produces excess growth hormones Errors in Metabolism

19. A serious degeneration of the nervous system with an onset from age 40 onward - Fatal, no cure Gene has been found Huntington’s Disorder Would you want to know? WHY??? Woody Guthrie

20. Mutated gene occurs only on the X chromosome X-Linked Recessive

21. Heterozygous females are phenotypically normal Males are affected because they have only one allele for the trait (on the X chromosome) and it can be recessive. X-Linked Recessive

22. Color-blindness Baldness X-Linked Recessive

23. Inability of blood to clot because genes do not code for clotting agent(s) Hemophilia A

24. Queen Victoria: a Carrier

25. Afflicted persons need frequent transfusions and infusions of artificial clotting agents Internal bleeding from falls or bruising the most serious Cummulative scarring may restrict movement Hemophilia A

26. Similar to X-linked recessive alleles, except the allele is also expressed in heterozygous females Examples: faulty enamel (of the teeth) trait X-Linked Dominance

27. Aneuploidy = one extra or one less chromosome, may affect one of every two newly fertilized eggs Polyploidy = three or more of each chromosome, is common in plants but is lethal to the zygote if it occurs in humans Patterns of Inheritance

28. Meiotic Errors • Nondisjunction- homologues don't separate in meiosis 1

29. Trisomy 21 • Exception leading to Down Syndrome • Occurs more frequently in children born to older women and men • 1: 80 births after 40 yrs • 1: 40 births after 45 yrs

30. Most children show mental retardation Many lead productive lives Full of love for others 40% have heart defects Down Syndrome

31. Non-disjunction in Sex Chromosomes • Homologues don't separate in meiosis 1

32. XO Females with only one X chromosome, mostly due to nondisjunction in father Most are spontaneously aborted Sterile, short stature, heart defects, premature aging, shorter lives YO = LETHAL Turner Syndrome

33. XXY condition Most from non-disjunction in mother Tall, some mental slowness Poor male sex organ development; breast development; usually sterile Klinefelter Syndrome

34. XYY condition Fertile, tall, slight retardation, increased strength & aggression NOT predisposed to crime - a fallacy Jacob Syndrome

35. Changes in Chromosome Structure • Translocation • Transfer of a piece of one chromosome to another

36. Deletions Loss of a chromosome region by viral attack, chemicals, irradiation, or other environmental factors Changes in Chromosome Structure

37. Deletion or translocation of material from 5th chromosome “Cry of the Cat” (French) - sound many children make when crying Severe mental retardation; internal problems Cri-du-Chat

38. Inversion Alters the position and sequence of the genes so that gene order is reversed Changes in Chromosome Structure

39. Duplications Occurs when a gene sequence is in excess of the normal amount. Changes in Chromosome Structure

40. Fragile X syndrome Mental retardation Repeats that may block expression of gene on X chromosome Duplications

41. Mistake Summary

42. Designed by Anne F. Maben These images are for viewing only and may not be published in any form