1. Biology Ch. 14
Human Heredity

2. I. Human Chromosomes
- heredity in humans is the same as in other organisms
- most genetic diseases are recessive and rare

3. A. Karyotype
- A chart showing a complete diploid set of paired homologous chromosomes

4. 1. Sex Chromosomes
- pair of chromosomes that determine an individual’s sex
XX - female XY – male
- other sex determination systems exist

5. 2. Autosomes - the other chromosome pairs except the sex chromosomes
- Humans have _____ autosomes.

6. B. Inheritance of Human Traits
1. Dominant and Recessive Alleles
- Many human traits are controlled by dominant and recessives alleles.
- Ex. MC1R gene helps determine skin and hair color.
Red hair results from being homozygous recessive for the MC1R gene.

7. 2. Codominance - Both alleles are expressed in heterozygotes.
- Ex. Type AB blood express IA and IB alleles.
Type A
Type AB
Type B
Type O

8. 3. Sex-linked Traits
- Traits controlled by genes located on the X sex chromosome.
- Ex. Red-green colorblindness
What People with Regular Vision See
What Red-Green Colorblind People See

9. 3. Sex-linked Traits
- Traits controlled by genes located on the X sex chromosome.
- Ex. Red-green colorblindness
- Ex. Hemophilia

10. Queen Victoria’s Family

11. Pedigree of Europe’s Royal Families

12. 4. X-Chromosome Inactivation
- In females, 1 X chromosome is inactivated resulting in a mosaic of gene expression in heterozygotes
- Ex. Calico cat

13. 4. X-Chromosome Inactivation
- In females, 1 X chromosome is inactivated resulting in a mosaic of gene expression in heterozygotes
- Ex. Sweat gland mosaic
Fertilized Egg
Early Cell Division
X Chromosome Inactivation
Mitosis
Maternal X
Paternal X
Barr Body
Skin lacking sweat glands
Normal skin

14. C. Pedigrees - A chart used to show inheritance patterns
Pedigree chart of Queen Victoria’s family showing the inheritance of hemophilia.

15. II. Human Genetic Disorders
- A mutation in DNA’s base sequence changes a protein’s structure by changing the sequence of amino acids.
A single amino acid substitution in a protein causes sickle-cell disease.

16. A. Genetic Disorders Caused by Single Genes
1. Sickle-Cell Disease
- affects hemoglobin, the protein that carries O2 in red blood cells
- causes blood blockages, pain, tissue and organ damage

18. HbS Alelle Frequency(%)
- most common in sub-Saharan Africa.
- 1 out of 10 African-Americans are carriers.
- Heterozygous advantage: carriers are resistant to malaria.
Malaria
HbS Alelle Frequency(%)
> 12.5
7.5-10
0-2.5

19. 2. Cystic Fibrosis (CF)
- affects CFTR, a transport protein in the cell membrane
- causes excessive production of thick mucus in lungs and digestive system

20. 3. Huntington’s Disease - rare, dominant, nervous system disorder
- symptoms (uncontrollable movements, mental deterioration) appear late in life
Huntington’s Disease
Woody Guthrie

21. B. Chromosomal Disorders
Nondisjunction:
- a failure of homologous chromosomes to separate during meiosis
- results in gametes with missing or extra chromosomes

22. B. Chromosomal Disorders
Nondisjunction:

23. Down Syndrome (Trisomy 21)

24. Incidence of Down Syndrome10 20 30 40 50
100
200
300
400
Age of Mother (years)
Number per 1000 Births

25. Turner’s Syndrome (Monosomy X)

26. XYY Syndrome

27. Trisomy X (XXX)

28. Klinefelter’s Syndrome (XXY)

29. Down Syndrome (Trisomy 21)

30. Normal Female

31. Edward’s Syndrome (Trisomy 18)

33. III. Selective Breeding
- Humans have used selective breeding for thousands of years to produce new varieties of crops and domestic animals.
Maize was domesticated from its wild grass ancestor more than 8,700 years ago.

34. III. Selective Breeding
- Humans have used selective breeding for thousands of years to produce new varieties of crops and domestic animals.
The dog was domesticated from the grey wolf over than 14,700 years ago.

35. A. Hybridization Nondisjunction:
- a failure of homologous chromosomes to separate during meiosis
- results in gametes with missing or extra chromosomes

36. B. Inbreeding Nondisjunction:
- a failure of homologous chromosomes to separate during meiosis
- results in gametes with missing or extra chromosomes

37. C. Polyploidy Nondisjunction:
- a failure of homologous chromosomes to separate during meiosis
- results in gametes with missing or extra chromosomes

38. The
End

39. Human Chromosomes (23 homologous pairs)

40. Epistasis: Black, Chocolate, and Golden Labrador Retrievers