1. Human Inheritance Chapter 14 Biology Concepts and Applications, Eight Edition, by Starr, Evers, Starr. Brooks/Cole, Cengage Learning 2011.

2. Human Chromosomes  Human body cells have 23 pairs of homologous chromosomes 22 pairs of autosomes 1 pair of sex chromosomes

3. Autosomes and Sex Chromosomes  Paired autosomes Same in length and shape Have the same centromere location Carry the same genes along their length  Sex chromosomes Identical in human females (XX) Nonidentical in human males (XY)

4. Sex Determination  SRY gene on the Y chromosome Basis of male sex determination Expression initiates synthesis of testosterone Hormone causes embryo to develop into a male  If an embryo has no Y chromosome (no SRY gene), it develops into a female

5. Sex Determination Pattern

6. Sexual Development in Human Embryos

7. Fig. 11.2, p.170 At seven weeks, appearance of structures that will give rise to external genitalia At seven weeks, appearance of “uncommitted” duct system of embryo Y chromosome present Y chromosome absent Y chromosome present Y chromosome absent penis 10 weeks vaginal opening birth approaching uterus ovary testis penis vagina

8. Autosomal Inheritance Patterns  Some alleles on autosomes are inherited in simple Mendelian patterns associated with specific phenotypes  Certain mutated forms of alleles give rise to genetic abnormalities or genetic disorders  Table 14.1 in Text for Examples

9. Autosomal Dominant Inheritance

10. Autosomal Recessive Inheritance

11. Key Concepts: AUTOSOMAL INHERITANCE  Many genes on autosomes are expressed in Mendelian patterns of simple dominance

12. X-Linked Inheritance Patterns  Certain dominant and recessive alleles on the X chromosome are inherited in Mendelian patterns  Mutated alleles on the X chromosome contribute to more than 300 known genetic disorders  Males can’t transmit recessive X-linked alleles to sons (son receives X chromosome from mother)

13. X-Linked Inheritance Patterns

14. Hemophilia A  X-linked recessive Pedigree  chart showing the pattern of inheritance of a trait through generations in a family Interfere with blood clotting. Affect 1:7500 people.

15. Fig. 11.8, p.174 Green  Carriers Red  Diseased

16. Color Blindness

17. Key Concepts: SEX-LINKED INHERITANCE  Some traits are affected by genes on the X chromosome  Inheritance patterns of such traits differ in males and females

18. Heritable Changes in Chromosome Number  Chromosome number of a parental cell can change permanently  Often caused by nondisjunction Failure of one or more pairs of duplicated chromosomes to separate during meiosis

19. Nondisjunction in Meiosis

20. chromosome alignments at metaphase I NONDISJUNCTION AT ANAPHASE I alignments at metaphase II anaphase II n + 1 n - 1 CHROMOSOME NUMBER IN GAMETES Stepped Art Fig. 11-13, p.178

21. Aneuploidy  Aneuploidy  Cells with too many or too few copies of a particular chromosome In humans, the most common aneuploidy (trisomy 21) causes Down syndrome  Most other human autosomal aneuploids die before birth

22. Aneuploidy: Trisomy 21 (Down Syndrome)

23. Fig. 11.14, p.179

24. Polyploid  Polyploid  having 3 or more of each type of chromosome characteristic of the species Example: XXY (1:500 males) Klinefelter syndrome Example: XYY

25. Polyploid  XXY (1:500 males) Klinefelter syndrome  Characteristics Overweight, tall, within normal range of intelligence Make more estrogen and less testosterone than normal males Small testes and prostate glands, low sperm counts, sparse facial and body hair, high-pitched voices, and enlarged breast Testosterone injections during puberty can reverse these traits  XYY Normal OR May be taller with mild mental impairment

26. Animation: Autosomal dominant inheritance

27. Animation: Autosomal recessive inheritance

28. Animation: Human sex determination

29. Animation: Pedigree diagrams

30. Animation: X-linked inheritance