Complex Inheritance and Human Heredity

1. Complex Inheritance and Human Heredity Chapter 11

2. We inherit traits from our parents, we get half of our genes from mom, and half from dad • Alleles are either recessive (lowercase) or dominant (uppercase) • Homozygous recessive, homozygous dominant, heterozygous Let’s review!

3. Autosome/Autosomal: Any chromosome other than the sex chromosomes (X & Y). Chromosomes designated 1-22. • Carrier: An individual who is heterozygous for a recessive disorder • Pedigree: A diagram that traces the inheritance of a particular trait through several generations of the same family New Words!

4. Basic patterns of inheritance Genetic Disorders

5. An abnormal condition that a person inherits through their genes • Can be caused by either changes in DNA, or an extra or missing chromosome • Genetic disorders can be recessive or dominant Genetic Disorders

6. Two recessive alleles, one from each parent • If an individual is heterozygous, they are a carrier (this means they could pass it on even if they don’t have it!) • BB – Normal • Bb – okay, but a carrier • bb – disease • Often skips a generation Recessive Disorders

7. Affects cell membrane protein, water cannot diffuse from cells • the body produces an abnormally thick mucus in the lungs • Chromosome 7 • Medication, strict diet, enzyme replacement • Death is usually caused by lung complications Cystic Fibrosis

8. Absence of enzyme that breaks down fatty substances • Chromosome 15 • Buildup of fatty acids in brain • Cherry red spot on back of eye • Causes deafness, blindness, severe retardation, and death usually by age 4 • Most carriers choose to avoid birth because there is no cure Tay-Sachs

9. Caused by altered genes, resulting in the absence of the skin pigment melanin in hair and eyes • White hair • Very pale skin • Pink pupils Albinism

10. Recessive genetic disorder characterized by the inability of the body to digest galactose. • People with this disorder should avoid milk products Galactosemia

11. The mutation for cataracts (c) occurs on a gene represented by the letter E. Owls that are homozygous for the mutation (EcEc) exhibit cataracts. Owls that are homozygous for normal eyes are EE and owls that are carriers of the mutation but do not exhibit cataracts are EEc. What percentage of the offspring in a cross between parents with the genotypes EE and EcEc will exhibit cataracts? A. 0% B. 25% C. 50% D. 75% OGT

12. Caused by dominant alleles • Those who do not have the disorder are homozygous recessive. • BB – have disease • Bb – have disease • bb – normal Dominant Disorders

13. Affects the nervous system • Deterioration of brain tissue, usually begins between age 30 and 40 • Chromosome 4 • No cure, but have medications to cope with symptoms • People usually die 15-20 years after onset of degeneration Huntington’s Disease

14. causes small body size and limbs that are comparatively short, most common type of dwarfism • Chromosome 4 • 75% born to parents of average size • When this happens it is due to a gene mutation Achondroplasia

15. Genetic disorders To Test or Not to Test?

16. You will need one worksheet and one index card • Find the rest of your family based on the number on your cards • Complete the worksheet as a group and be prepared to discuss your answers as a class Choosing Thomas

17. Pedigrees

18. A diagram that traces the inheritance of a particular trait through several generations of the same family • Allows us to use family trees and affected individuals to predict the risk of disease in future offspring Pedigrees

19. Male: • Female: • Affected Individual: • Carrier: • Mating: • Siblings: • Divorced/Separated: • Deceased: Symbols

20. Individuals are in birth order from left to right (oldest at left, youngest on right) • Individuals are numbered • Generations are numbered with roman numerals • When referring to an individual, use the generation number and then the individual number • II-4

21. Grandparents Grandparents I Parents II Aunts, Uncles Aunts, Uncles Example of a Pedigree III Brother You Do any disorders run in this family??

22. Whether a family has an autosomal or sex-linked disease or disorder • If the trait is dominant or recessive • Autosomal: appears in both sexes equally • Sex-linked disorder: allele is located only on the X or Y chromosome. Most sex-linked genes are on the X chromosome and are recessive • So who would have an X-linked disorder more often, boys or girls? What can you tell from a pedigree?

23. Complex patterns of inheritance

24. Basic patterns of inheritance involve… • The passing of dominant or recessive traits • Disorders that are recessive require: • 2 recessive alleles, 1 from mom, 1 from dad • A normal person who carries the gene could pass it on • Disorders that are dominant require: • 2 dominant alleles, 1 from mom, 1 from dad OR • 1 dominant allele (heterozygous) • There are no carriers for these disorders, you either have it or you don’t! Let’s Review!

25. These disorders are autosomal • Chromosomes 1-22 • Geneticists use a diagram called a pedigree to trace familial traits and predict the inheritance of the trait in future offspring Let’s Review!

26. Sometimes the laws and principles of genetics established by Gregor Mendel do not always explain the inheritance patterns seen in an organism.

27. Neither allele is completely dominant nor completely recessive • Heterozygous phenotype is a blend of the two homozygous phenotypes • a mix in physical appearance between the dominant and the recessive Incomplete Dominance

28. Both alleles are completely expressed in the heterozygous condition. • Sickle Cell Codominance

29. Abnormal hemoglobin causes a person’s red blood cells to be sickle shaped • The shape causes clots and blockages, they also carry less oxygen • The allele for the disease is codominant with the normal allele (heterozygous) • People who are heterozygous for sickle cell also have a higher resistance to malaria Sickle Cell Anemia

30. rr – all sickle shaped cells • Rr– mixture of both • RR– normal shaped cells Sickle Cell

31. Codominant or Incomplete?

32. Sometimes, there are 3 or 4 alleles that code for a single trait • Blood Groups • This doesn’t mean a person has more than 2 alleles for the trait, just that more than 2 exist in the population • 1 gene, more than 2 alleles Multiple Alleles

33. 3 forms of the allele • IA – type A • IB – type B • i – type O • i is recessive to IA and IB • IA and IB are codominant • IAIB – type AB Blood Groups

34. Heterozygous Homozygous IAIA – Type A IBIB – Type B ii – Type O • IAi – type A • IBi – Type B • IAIB– type AB Blood Groups

35. A scientist uses a microscope to examine two slides of living bacteria. Each slide contains a different type of bacteria. While the cells on the first slide are moving rapidly, the cells on the second slide are stationary. Based on these observations, the cells on the second slide most likely have no A. nucleus B. flagella C. chloroplasts D. mitochondria OGT

36. Genes that are found on the X chromosome • Expressed more in males because they only have one X chromosome (XY) compared to females (XX) Sex-Linked Traits

37. Recessive sex-linked disorder • Takes a long time for blood to clot (body lacks proteins involved in clotting) • Very rare in females because she would need to have both X chromosomes with the recessive trait. Hemophilia

38. Patricia is a healthy carrier of hemophilia and Sam is completely healthy. Complete the Punnett square below. • Mom’s genotype: • Dad’s genotype: • What is the probability of getting: • Daughter with hemophilia? • Son with hemophilia? • Carrier? • Healthy child?

40. Recessive X-linked trait • Male only needs one copy of this allele in order to be colorblind. • Female would need to have two copies of the recessive allele. • It is very rare to find a color blind female. • Mothers pass this to their sons • Father pass it to their daughters Red-Green Colorblindness

41. Judy is homozygous recessive for colorblindness and Dennis is healthy. Complete their Punnett square below. • Mom’s genotype: • Dad’s genotype: • What is the probability of getting: • Colorblind daughter? • Color blind son? • Carrier? • Heterozygous child?

42. Baldness is X-linked Recessive Grandpa bald = XbYXGrandma = XBXB Daughter = XBXb marries Male = XBY Sons? 50% XB(normal) 50% Xb(bald) This is why men should look to their mom’s dad for probability of baldness. But beware grandma could be a carrier too! Baldness

43. At 25°C, water has a density of 1.0 g/mL and vegetable oil has a density of 0.90 g/mL. How would a substance with a density of 0.95 g/mL behave when placed in both oil and water? A. a decrease in air quality. B. a decrease in biodiversity. C. an increase in deciduous tree species. D. an increase in nighttime temperatures. OGT

44. What’s different?

45. Cell division during which sister chromatids fail to separate properly • If this occurs during Meiosis I or II then the resulting gametes will not have the correct number of chromosomes • Nondisjunction occurs in both autosomes (body cells) and in gametes • Trisomic: one extra chromosome (only 3 trisomies that result in survival after birth) • Monosomic: one missing chromosome (usually lethal, except in Turner’s Syndrome) Nondisjunction

47. Chromosome 21 • Trisomy • Can be moderate or severe • Short stature, heart defects, and mental disability • Correlated with mother’s age, can be from nondisjunction of father’s chromosome 21 Down Syndrome

48. Autosomal Sex Chromosomes Klinefelter Syndrome: XXY Male sex organs; unusually small testes, sterile. Breast enlargement and other feminine body characteristics. Normal intelligence. Trisomy X: XXX 1:1000 live births - healthy and fertile - usually cannot be distinguished from normal female Monosomy X: Turner’s Syndrome 1:5000 live births; the only viable monosomy in humans - women with Turner's have only 45 chromosomes!!! XO individuals are genetically female, however, they do not mature sexually during puberty and are sterile. Short stature and normal intelligence. (98% of these fetuses die before birth) • Patau Syndrome: Trisomy 13 • serious eye, brain, circulatory defects as well as cleft palate. 1:5000 live births. Children rarely live more than a few months • Edwards’s Syndrome: Trisomy 18 • almost every organ system affected 1:10,000 live births. Children with full Trisomy 18 generally do not live more than a few months. Other Examples

50. The environment can have an influence on how genes are expressed • Toxic agents • Diet and exercise • Sunlight and water • Temperature • Medications • Conditions can cause a gene to shut down or turn on I got the “fat” gene. Environmental Factors