Human Genetics

2. Human Genetics Inheritance in humans Male/female Multiple Alleles Inherited diseases Twins Sex-linked traits

3. Single genes (widows peak)

4. Why is a guy a guy?

6. Color blindness is also Sex-Linked

7. Hemophilia

8. Inheritance in humans • A person receives 23 chromosomes from each parent (46 total) • 1 gene for each particular trait from each parent • Genes combine to determine traits (characteristics) • Instruct body cells to make certain chemicals = (proteins) • For example: special proteins (enzymes) make pigment in the iris of the eye

10. Multiple alleles

11. Who Has Which Blood Type?

12. Multiple alleles • Co-dominant – when 2 different genes are both equally dominant– • 4 major blood groups = A, B, AB, O . • O is recessive, while A and B are co-dominant

13. Phenotypes vs. Genotypes • 4 major blood groups = A, B, AB, O • Phenotype A could be Genotype AA or Ao • Phenotype B could be Genotype BB or Bo • Phenotype AB can only be Genotype AB • Phenotype O can only be Genotype oo

14. Inheritance in humans • Allele = each form of a gene • Some genes (traits) have multiple alleles • Skin color has 3 or more • Controls amount of melanin (pigment) in the skin cells • Any one individual inherits only 2

15. Genetic disorders • Non disjunction = failure of a chromosome pair to separate during meiosis • Body cells receive either more or fewer chromosomes than normal • May result in certain disorders • Down’s Syndrome = body cells have an extra chromosome-21 • Trisomy-21 (3 instead of 2) • May have various physical problems and some degree of mental retardation

16. Genetic disorders • Down’s Syndrome • Trisomy-21 • A karyotype (page 117)is a picture of all the chromosomes in a dividing cell. amniocentesis

17. Screening for genetic disorders • Amniocentesis • Drawing a small amount of amniotic fluid from the sac surrounding an unborn baby (fetus) • Chromosomes of cells from the fluid can be examined under microscope

18. twins • Fraternal twins (dizygotic) • 2 separate ova are fertilized at same time • Can be same or different sex • Identical twins (monozygotic) • Develop from single zygote (fertilized ovum) • Always the same sex • Can occur up to 12 days after conception

19. Identical twins - monozygotic • One fertilized egg splits into two separate people-with the same genes- • A natural clone

20. Fraternal Twin –Dizygotic • Two – or more eggs which are fertilized by two or more sperm cells • No more alike than any other brother or sister

21. Others (include) • Muscular dystrophy • Huntington disease • Cystic fibrosis • Hemophila (sex linked)

22. Sex-linked traits • Traits that are usually carried on X chromosome • Females less like to inherit • Have XX • X carries other genes besides feminine traits • Recessive genes are hidden by dominant genes of other X • Males more likely to inherit • Y carries mostly masculine traits • Cannot override genes carried on X

23. Sex Linked traits

24. Pedigrees – page 119

28. Inherited diseases • sickle cell anemia • Co dominant gene • Caused by mutation of gene for hemoglobin (red pigment in red blood cells that carries O2 • Over time, affected cells become rigid & crescent-shaped

29. Sickle cell disease/anemia

31. Sex Determining Chromosomes • Noted different shapes of sex chromosomes: X, Y • Female = XX • Male = XY

32. Male/Female • XX = normal female • XY = normal male • Sperm determines sex of the individual • X seems to be essential for life • No one has been born without at least one X chromosome

33. Abnormalities of inheriting sex chromosomes • X0 = female in appearance • XXY = male in appearance • Both are sterile – • not able to have children • (There are other abnormalities) • (XYY for example)

34. Glowing Plant: Natural Lighting without Electricity