1. Chapter 12 PATTERNS OF HEREDITY AND HUMAN GENETICS

2. Objectives Interpret a pedigree Determine human genetic disorders that are caused by inheritance of recessive alleles Predict how a human trait can be determined my a simple dominant allele SCS:

3. Mendelian Inheritance of Human Traits How can we trace traits in our family? Geneticists use a tool called a pedigree (graphic representation of genetic inheritance)

4. Male Female Marriage Heterozygous or carrier

7. I, II, III – represent generations pedigrees are used by genetic counselors to help trace genetic disorders and other traits

8. Simple Recessive Heredity most genetic disorders are caused by recessive alleles (rare) – you have to receive 2 alleles, 1 from mom and 1 from dad in order to inherit the disorder

10. Examples Cystic Fibrosis (CF) 1/2000 are affected by CF, 1/200 are carriers characterized by a defective protein that causes mucas to build up in the lungs

11. Tay Sachs Disease common in Ashkenazi Jews characterized by the absence of an enzyme that breaks down fat in the brain most children die by the age of 5

12. Simple Dominant Heredity only need a single dominant allele for the trait to be expressed

13. examples of dominant traits in humans: unattached ear lobes, tongue rolling, hitchhikers thumb, mid digit hair

14. Examples of dominant genetic disorders Huntington’s Disease doesn’t affect individuals until their 30-50 years of age characterized by the breakdown of areas of the brain

16. 12-2 Whey Heredity follows different rules Distinguish between incompletely dominant and codominant alleles Compare multiple allelic and polygenic inheritance Analyze the pattern of sex-linked inheritance Summarize how internal and external environments affect gene expression SCS:

17. Complex Patterns of Heredity most traits observed are not a result of simple dominant/ recessive inheritance

18. Types Incomplete dominance- heterozygous condition results an intermediate phenotype or “mixing”; neither allele is completely dominant over the other

19. Example: Snap dragons. Homozygous Red and white flowers are crossed, and they produce all pink offspring

20. Codominance- both alleles are expressed equally Example: Cows. Homozygous Red and white cows are crossed (mated), and they produce offspring that appear pink from a distance because they both red and white hairs

21. Multiple Alleles- traits controlled by two or more alleles

22. Sex linked inheritance- traits controlled by genes located on the sex chromosomes Thomas Morgan was the first to discover  Worked with fruit flies

23. Problems involving sex linkage In fruit flies, red eyes are dominant over white example of a cross: X R X r x X r Y

24. Polygenic Inheritance- traits that are controlled by more than 1 gene Genes might be on the same or different chromosomes

25. Other factors influence the expression of genes Environmental Influences External Environmental (temp. nutrition, light, chemicals, infectious agents) Internal Environment (hormones, age) genetic makeup determines the potential to develop and function

26. 12-3 Complex Inheritance of Human Traits Compare codominance, multiple alleleic, sex- linked, and polygenic patterns of inheritance in humans Distinguish among conditions in which extra autosomal or sex chromosomes exist SCS:

27. Complex Inheritance of Human Traits Codominance- Sickle Cell Anemia  most common in black Americans

28.  Characterized by the sickling of red blood cells, which hampers circulation and affects oxygen levels of the blood  In malaria prone areas people with this gene are protected against malaria

29.  Homozygous conditions results in full blown SC, and medication has to be taken  Heterozygous condition results in a mild case, may not need medication

30. Multiple Alleles Blood types There are 4 blood types in humans (A, B, AB, and 0) the type of marker (protein on your red blood cells determine your blood type)

31. PhenotypesGenotypes Type AI A I A or I A i Type BI B I B or I B i Type ABI A I B Type Oii

32. knowing your blood type is important:  blood transfusions, child birth, blood donations

33. Type Blood Can Receive A A, O BB, O ABAB, O, A, B Universal recipient: AB Universal Donor: O

34. Sex Linkage Some human traits are determined by genes found on the sex chromosomes (mostly X) Examples of sex linked traits: Red/Green Color Blindness- can’t differentiate red from green recessive disorder More males have it because they only need one allele

35. Hemophilia bleeders disease; blood does not clot naturally so a person can bleed to death 1/10,000 males are afflicted, only 1/ 100 million females are affeced

36. Polygenic Traits example include skin color, eye color,

37. Changes in chromosome number Normally humans have 46 chromosomes, but sometimes during replication, chromosomes do not separate correctly

38. Geneticist use a tool called a karyotype to determine if an extra chromosome is present Take a sample of a person’s DNA and line up the metaphase chromosomes

43. Examples of Disorders Downs Syndrome (Trisomy 21) a result of an extra chromosome in the 21st pair some degree of mental retardation

44. Turners Syndrome XO, female, infertile Kleinfelter’s XXY, Male, infertile