Presentation Transcript

1. Patterns of Heredity and Human Genetics

   A Look at Genetic Complexities Chapter 12 Notes

2. What happens when heredity follows different rules?

   The Exceptions to Mendel’s Rules Section 12.2
3. Section Objectives At the end of this lesson, YOU will be able to: Distinguish between alleles for incomplete dominance and codominance. Explain the patterns of multiple allelic and polygenic inheritance. Analyze the pattern of sex-linked inheritance. Summarize how internal and external environments affect gene expression.
4. Remember Punnett Squares dd Heterozygous Chin Dimple (male) X No Chin Dimple (female) d d D Dd d
5. Remember Mendel? His 4 conclusions were: The Rule of Unit Factors The Rule of Dominance The Law of Segregation The Law of Independent Assortment http://www.pbs.org/wgbh/nova/orchid/images/amat_mendel.jpg
6. Exceptions to Mendel’s Rules Sometimes, patterns of inheritance are not as simple as Mendel’s Rules imply. The exceptions to Mendel’s Rules are when nature uses a different method of determining traits.
7. Gene Linkage The Law of Independent Assortment can be broken when genes are found close together on the same chromosome. The genes will appear linked, or show up together. The closer the genes are to each other the more they will be inherited together.
8. Breaking the Rule of Dominance Usually, a dominant gene produces a protein for the trait. The recessive allele either produces a nonfunctional protein or no protein at all. So we see the dominant trait in hybrids because it is the only trait expressing a protein. DNA mRNA mRNA Protein
9. Incomplete Dominance When heterozygous individuals show an intermediate phenotype between the two homozygous phenotypes. Having one copy of a gene does not produce enough protein to completely mask the recessive allele. http://www.miracosta.edu/home/rmooney/Mendelian%20genetics_files/slide0015_image033.jpg
10. Incomplete Dominance r r Snapdragons If you cross a red flower and a white flower, the resulting hybrid will be pink. RR = red flower rr = white flower Rr = pink flower If you cross two pink flowers (Rr), you get: 25% Red Flowers 50% Pink Flowers 25% White Flowers R Rr Rr R Rr Rr R r R RR Rr r Rr rr
11. Incomplete Dominance Hair Straight (HH) Wavy (Hh) Curly (hh)
12. Codominance When a heterozygous individual shows the phenotypic traits of both alleles. Both alleles produce a protein, which are seen in the hybrids. The traits do not blend!
13. Codominance B B Feather Color in Chickens A black chicken would be BB. A white chicken would be WW. A hybrid, BW, would have a checkered appearance. Both white and black pigments are seen in the offspring. BW BW W BW BW W B W BB BW B BW WW W
14. Codominance Sickle Cell
15. Multiple Alleles When a trait is controlled by more than two alleles. Each individual only owns two alleles, but others in the population may possess different types.
16. cch C ca ch cbcb- Bugs Bunny Multiple Alleles Fur Color in Rabbits C = Dominant allele ch = Himalayan fur cch = Chinchilla fur ca = Albino fur
17. Multiple Alleles Blood Types IA, IB, or i IAIA or IAi IBIB or IBi IAIB ii
18. Polygenic Traits When one trait is controlled by more than one gene. The genes may be on the same or different chromosomes. Both genes have a single phenotypic effect.
19. Polygenic Traits Coat Color in Labrador Retrievers Controlled by two different genes, the B gene and the E gene. A dihybrid cross of two black labs (BbEe x BbEe) results in: 9 Black Pups 3 Chocolate Pups 3 Golden Pups 1 Golden Pup with a brown nose and light eyes. http://www.oakhillkennel.com/library/color.html
20. Polygenic Traits Eye Color Brown Gene Green Gene
21. Multifactorial Traits When traits are determined by several factors from the genetic makeup and the organism’s environment. The genes only represent the potential. Environmental influences turn on the genes at different times and in different amounts.
22. Multifactorial Traits Temperature, nutrition, light, chemicals, and infections can influence gene expression. Arctic Foxes have coats that change color due to temperature.
23. Multifactorial Traits Height, Intelligence, Cholesterol, Weight, Mental Illness, etc.

24. How do our chromosomes determine our sex?

    Sex Determination and Sex-linked Traits Section 12.2
25. Sex Determination Humans have a total of 46 chromosomes, or 23 pairs: 22 pairs of autosomes 1 pair of sex chromosomes Autosomes All of the chromosomes that determine the traits other than sex. Come in different sizes with different genes on them. Pairs 1-22
26. Sex Determination Sex Chromosomes Determine the sex of the individual. Pair 23 In females, these chromosomes match in the form of XX. In males, these chromosomes are different, as in XY.
27. Sex Determination The combination of sex chromosomes decides if you are a boy or a girl. A mother (XX) can only supply eggs that have an X chromosome. The father (XY) has some sperm with a X chromosome and some with a Y chromosome. X X XX XX X Y XY XY G- 50% XX; 50% XY P- 50% female; 50% male
28. Comparing the X and the Y
29. Sex-Linked Traits Genes that are located on the sex chromosomes. The X chromosome contain many important genes that are necessary for survival. The Y chromosome contains the SRY gene which determines maleness.
30. Sex-Linked Traits First observed in fruit flies (Drosophila). Fruit flies have either red or white eyes. Thomas Hunt Morgan noticed that all of the white-eyed flies were male. Therefore, eye-color in flies is a sex-linked trait.
31. Sex-Linked Traits Y Y Chromosome (no alleles) XR X Chromosome (red-eyed allele) Xr X Chromosome (white-eyed allele) Because the X chromosome is much larger than the Y, most sex-linked traits are on the X. When writing the alleles for these traits, you must include the chromosomes that the individual has:
32. Sex-Linked Traits Because males have only one X chromosome, they are more likely to get a single defective copy. XRY- red-eyed male XrY- white-eyed male XRY XrY
33. Sex-Linked Traits Because females receive two X chromosomes, they are more likely to get a dominant allele that can cover the effects of the recessive trait. A carrier female has a recessive allele but does not show the trait (heterozygous) XRXR Homozygous Red-eyed Female XRXr Carrier Female XrXr White-eyed female (rare)
34. Xr Y XR XR Xr XR Y XR XR Xr XR Y Sex-Linked Punnett Squares Homozygous Red-eyed Female x White-eyed Male XRXR XrY G- 50% XRXr 50% XRY P- 50% red-eyed female 50% red-eyed male
35. XR Y XR XR XR XR Y Xr XR Xr Xr Y Sex-Linked Punnett Squares Heterozygous Red-eyed Female x Red-eyed Male XRXr XRY G- 25% XRXR 25% XRXr 25% XRY 25% XrY P- 50% red-eyed female 25% red-eyed male 25% white-eyed male

36. How do pedigrees show inherited traits within families?

    Understanding Pedigrees Section 12.1
37. Pedigrees A graphic representation of traits inherited within a family. Allows scientists to trace the history of a genetic disorder. Uses symbols to represent individuals. Circles represent females Squares represent males If the symbol is shaded, the individual is affected by the trait. Normal Female Normal Male Affected Female Affected Male
38. Pedigrees Inherited traits can be followed from generation to generation. Horizontal lines connect two individuals who have mated. Vertical lines represent the offspring of a union. I Bb Bb 1 2 Bb bb BB Bb II 1 2 3 4 5
39. Rules of Pedigrees Sex-Linked vs. Autosomal If more males are affected by a trait than females, it is probably sex-linked. If it affects males and females equally, it is probably autosomal.
40. Rules of Pedigrees Dominant vs. Recessive If a trait skips a generation, it is recessive. If the trait is found in each generation, it is probably dominant.
41. Rules of Pedigrees Identifying Genotypes If any males are carriers, the trait is autosomal. If a male has a sex-linked trait, his mother was probably a carrier.
42. Autosomal Recessive Affects males and females equally. Skips generations (appears in some generations but not in others). Males can be carriers
43. Autosomal Dominant Affects males and females equally Does not skip any generations.
44. Sex-Linked Recessive Affects males more than females. Skips generations. Must use the chromosomes (XY or XX)
45. Example #1: Albinism Are males affected more frequently that females? NO Autosomal Disorder Does the disorder skip generations? YES (P1) Recessive Disorder A- normal a - albino Autosomal Recessive
46. Example #2: Hemophilia Are males affected more frequently that females? YES Sex-Linked Disorder Does the disorder skip generations? YES + = normal H = hemophilia Recessive Disorder Sex-Linked Recessive
47. Pedigree Practice Genetic Trait: ACHOO (Sneezes in response to light) A #1- Is this trait sex-linked or autosomal? #2- Is this trait dominant or recessive? B #3- What is the genotype of individual A? #4- What is the genotype of individual B? C #5- What is the genotype of individual C? #6- What is the genotype of individual D? D
48. Karyotype A picture of an individuals chromosomes. Homologous chromosomes are paired up. Pairs are arranged by size. Karyotypes can help diagnose chromosomal disorders.
49. Karyotypes When arranging the chromosomes: Autosomal Chromosomes are placed in order by size. The Sex Chromosomes are pair 23.
50. Karyotypes What to look for: The Sex Chromosomes: Male (XY) or Female (XX) Is there an odd number (XXY, XYY, XO, XXX) The Autosomes Are there two or three chromosomes for pair 21? Trisomy 21  Down Syndrome
51. Example #1 Number of Autosomes: Number of Sex-Chromosomes: Karyotype: Phenotype: 44 1 45 (X) Female- Turner Syndrome
52. Example #2 Number of Autosomes: Number of Sex-Chromosomes: Karyotype: Phenotype: 44 3 47 (XYY) Male Jacob’s Syndrome
53. Example #3 Number of Autosomes: Number of Sex-Chromosomes: Karyotype: Phenotype: 44 3 47 (XXY) Male Klinefelter Syndrome

54. What is the genetic basis for determining blood types?

    Understanding Blood Types
55. Blood Types in Humans Your body produces antibodies that attack any foreign objects within you. Usually, this fights bacteria, viruses, or fungi. All of your cells have antigens on their surface. Antigens are cellular nametags. Your body makes antibodies to fight off anything without your particular antigen.
56. Blood Types in Humans Your special antigens are made by your DNA. The antigens found on the red blood cells determine your blood type. Type A Type B Type AB Type O
57. Type A Blood
58. Type B Blood
59. Type AB Blood
60. Type O Blood
61. Rh Factor Another antigen on the surface of the RBC, is the Rhesus Factor. Named after it was discovered in Rhesus Monkeys People who have the Rh factor are positive. People without the Rh factor are negative.
62. Blood Donations Commonly, a person’s blood type combines their ABO type and Rh factor. Type A neg. Type O pos. rh rh rh Type A+ rh rh Type AB- rh rh Anti-A Anti-A Anti-A Anti-B Anti-B Anti-B Anti-Rh Anti-Rh Anti-Rh rh
63. Blood Donations A person cannot receive any blood that contains an antigen that they posses the antibody for. Type A individuals produce anti-B antibodies. Giving that person type B blood can have dangerous effects. The anti-B antibodies will cause the Type B blood to stick together. This is called clumping.
64. Blood Donations The Universal Recipient Produces no antibodies Can receive all types of blood Type AB+ The Universal Donor RBC’s have no antigens. Can give blood to anyone Type O-
65. Determining Blood Types IAIA x IBIB Type A Type B IB IB IAIB IAIB G: 100% IAIB IA IAIB IAIB IA P: 100% AB
66. Determining Blood Types Type AB x Type O IAIB ii i i IAi IAi G: 50% IAi 50% IBi IA IBi IBi IB P: 50% Type A 50% Type B
67. Determining Blood Types Hospital Mix-Up On a busy night at the Plainsboro Hospital, three families delivered three healthy baby boys. Unfortunately, the babies became mixed up during a rush and no one knows which baby belongs to which family. The nurses were able to take blood samples from each parent and each baby. Use your knowledge of blood type genetics to figure out which baby belongs to each family. Baby #1 belongs to the Jacksons Baby #2 belongs to the Robinsons Baby #3 belongs to the Jones
68. Characteristics of Blood System Codominance Both A and B are dominant. In a hybrid (AB) both types of antigen will be present. Multiple Alleles The ABO blood group has three alleles that produce four phenotypes. Polygenic Two genes control blood type: ABO and Rh factor

69. How do scientists follow genetic disorders in our genome?

    When Genetics Goes Wrong
70. Cystic Fibrosis Inheritance Autosomal Recessive Chromosome #7 Symptoms Abnormally thick mucous clogs pores in lungs, liver, pancreas.
71. Cystic Fibrosis Gene Therapy is a hopeful avenue of treatment for those with cystic fibrosis. Here’s how it works: Insert a working copy of the gene into a virus. Load the virus into an inhaler. Have the patient breath in the virus with the working copy. The virus then injects its DNA and the working CF gene into the patient’s cells What would be one potential downside to using gene therapy?
72. Phenylketoneuria (PKU) Inheritance Autosomal Recessive Chromosome # 12 Symptoms Victims are unable to metabolize phenylalanine properly. Leads to mental retardation.
73. Phenylketoneuria (PKU) All babies are tested for PKU in the first few days. How would being diagnosed with PKU affect your life?
74. Sickle Cell Inheritance AutosomalCodominant Chromosome # 11 Symptoms Defective hemoglobin becomes sickle-shaped Pain crises result when, cells clog blood vessels. http://www.ehponline.org/docs/2004/112-6/bloodcells.jpg
75. Sickle Cell AA Normal RBC/ Susceptible to Malaria AS Normal RBC and Sickle Cells/ Resistant to Malaria SS Sickle Cells/ Resistant to Malaria If sickle-cell is so bad, why has the gene not been taken out of the genome?
76. Huntington’s Disease Inheritance Autosomal Dominant Chromosome # 4 Symptoms Progressive neurological disorder. Nerve cells begin to deteriorate resulting in a loss of coordination. Begins in late 40’s or early 50’s.
77. Huntington’s Disease Huntington’s Disease is autosomal dominant. If one of your parents have it, you have a 50% chance of inheriting this progressive disorder. Question #1 Genetic testing can determine if you have inherited the dominant allele or not. If one of your parent’s had it, would you want to know if you have the disease or not? h h H Question #2 Should the results of genetic testing be given to employers by insurance companies? Is having the trait cause for firing somebody, even if they have not shown any symptoms? h
78. Color Blindness Inheritance Sex-linked Recessive X Chromosome Symptoms Unable to distinguish between red and green colors.
79. Color Blindness How would colorblindness affect the way you see the world? Protanopia Deuteranopia Tritanopia Normal Vision
80. Hemophilia Inheritance Sex-linked Recessive X Chromosome Symptoms Unable to clot properly because of missing Factor VII. Seen in the Royal family of Britain
81. Hemophilia
82. Down Syndrome Inheritance Chromosomal Nondisjunction Trisomy 21 Symptoms Mild mental retardation Simian Crease, Epicanthal fold, shorter limbs, poor muscle tone, protruding tongue
83. Down Syndrome Women over the age of 35 increase the chances of a DS child up to 1 in 378 (over 45 is 1 in 30). An amniocentesis extracts some fetal cells to prepare a karyotype. If you found out that your child would be born with Trisomy 21 (Down Syndrome), would you support terminating the pregnancy?
84. Other Traits in Humans Polygenic Traits Eye Color- 2 genes Skin Color- 3 genes Multifactorial Height Cholesterol Behavioral Traits