1. The Human Genome Chapter 14 – Human Heredity Human Chromosomes

2. Sex Chromosomes and Autosomes Two of the 46 chromosomes in humans are known as the sex chromosomes. X Chromosome Y Chromosome The remaining 44 chromosomes (22 pairs) are known as autosomes.

3. X and Y chromosomes

4. Factors to Consider in Pedigrees Is the trait located on a sex chromosome or an autosome? –Autosomal – not on a sex chromosome –Sex Linkage – located on one of the sex chromosomes Y-linked - only males carry the trait. X-linked (recessive) - sons inherit the disease from normal parents

5. Factors to Consider in Pedigrees How is the trait expressed? –Dominant - the trait is expressed in every generation. –Recessive - expression of the trait may skip generations.

6. Pedigree A pedigree is a chart which shows the relationships within a family, often highlighting the inheritance of a particular trait (such as heart disease or a widow’s peak hairline).

7. Pedigree Diagrams: I Basic Symbols

8. Pedigree Diagrams: II Basic Symbols for offspring and the expression of a trait. –The offspring are depicted below the parents. –Filling the symbol with black indicates the expression of the studied trait.

9. Pedigrees Draw the pedigree for a family in which: –A man with unattached earlobes (the trait of interest) and a woman with attached earlobes have three children; first a boy, then a girl, then another boy. –The two boys have attached earlobes, the daughter has unattached earlobes.

10. Blood types Antibodies – are protective proteins in the blood that identify “invaders”, (things that don’t belong) and attack them. The antibody name identifies what it will attack. Antigens – are chemical signals that identify “self” from “non-self”. Think of as a “flag” on the surface of the cell. Antibodies will attack any cell that has the “wrong” antigen (“wrong flag”).

11. ABO blood types antigens

12. ABO blood types antigens CLOTTING!! YOU’RE DEAD!!

13. ABO blood types antigens

14. ABO blood types antigens CLOTTING!! YOU’RE DEAD!!

15. ABO blood types antigens

16. ABO blood types antigens NO CLOTTING!! YOU’RE FINE!!

17. ABO blood types antigens

18. ABO blood types antigens CLOTTING!! YOU’RE DEAD!!

20. Summary of Blood types I A i X I B i –What blood types are these? –What blood types might their offspring have?

21. Summary of Blood types Type O blood (neither A nor B antigens) can donate to any blood type (universal donor). Type AB (no A or B antibodies) can receive blood from any donor (universal recipient).

22. Types of Genetic Disorders Autosomal Recessive Autosomal Dominant Autosomal Codominant Sex-Linked (X-linked) Recessive Chromosomal Disorders

23. Autosomal Recessive Genetic disorders Trait revealed only in homozygous recessive individuals. In equal numbers of males and females. Two unaffected heterozygous parents can have affected children.

24. Autosomal Recessive Genetic disorders Examples: –Albinism – lack of pigment in skin, hair, eyes –Cystic fibrosis – excess mucus in lungs –Phenylketonuria (PKU) – accumulation of phenylalanine in tissues, mental retardation –Tay-Sachs disease – lipid accumulation in brain cells, early death

25. Autosomal Dominant Genetic disorders Trait is revealed in every individual with a dominant gene. In equal numbers of males and females. Every affected individual has at least one affected parent.

26. Autosomal Dominant Genetic disorders Examples –Achondroplasia – dwarfism (one form) –Huntington’s disease – causes mental deterioration and uncontrolled movements. –Hypercholesterolemia – excess cholesterol in blood.

27. Autosomal Codominant Genetic disorders Trait caused by both alleles (neither allele is masked). Most important autosomal codominant genetic disorder is Sickle Cell Disease. –Bent and twisted (sickle-shaped) red blood cells tend to get stuck in capillaries. This damages tissues (brain, heart, spleen) and may be fatal. –Homozygotes and heterozygotes are affected to differing degrees.

28. Sex-Linked (X-linked) Recessive Genetic disorders Trait caused by genes found on the X- chromosome (entirely absent from the y chromosome). Because males have only one X chromosome, a single recessive allele (X a ) will cause the disorder. Females must have 2 copies of the disease allele (homozygous recessive) to have the disorder.

29. Sex-Linked (X-linked) Recessive Genetic disorders Examples of sex-linked recessive disorders –Colorblindness –Hemophilia –Duchenne Muscular Dystrophy

30. Sex-Linked (X-linked) Recessive Trait example Because the gene is found on the X chromosome and not the Y chromosome, you write the possible genotypes in the following way: Males –X A Y (dominant phenotype) –X a Y (recessive phenotype) – note it only takes one recessive allele for males to have the recessive phenotype because there is nothing on the Y chromosome to influence the trait.

31. Sex-Linked (X-linked) Recessive Trait example Females – X A X A (dominant phenotype) – X A X a (dominant phenotype) – X a X a (recessive phenotype) Females (XX) must have two copies of the recessive allele to have the recessive phenotype (heterozygotes have dominant phenotype).

32. Sex-Linked (X-linked) Recessive Trait example XRXr x XRY cross

33. Chromosomal Disorders In normal meiosis, homologous chromosomes separate from one another. In nondisjunction, the homologues fail to separate, resulting in gametes with too many or too few chromosomes.

34. Chromosomal Disorders Down Syndrome, also known as Trisomy 21, is a chromosomal disorder resulting from the nondisjuction of chromosome 21 in humans (the person has an extra chromosome 21)