1. Inheritance Patterns & Human Genetics Chapter 12

2. Chromosomes & Inheritance Section 12.1

3. What makes human males different than females? Sex chromosomes (X and Y) Sex chromosomes (X and Y) Male: XY Male: XY Female: XX Female: XX Gametes: Gametes: Egg: carry only X Egg: carry only X Sperm: carry either X or Y Sperm: carry either X or Y

4. Who Discovered Sex Chromosomes? Thomas Morgan Thomas Morgan Early 1900s Early 1900s Geneticist, embryologist, evolutionary biologist, Columbia University (USA) Geneticist, embryologist, evolutionary biologist, Columbia University (USA) Worked with fruit flies; discovered the role chromosomes play in inheritance Worked with fruit flies; discovered the role chromosomes play in inheritance

5. Sex Linkage: When genes are found on the sex chromosomes When genes are found on the sex chromosomes X-linked Genes: genes on the X chromosome X-linked Genes: genes on the X chromosome Y-linked Genes: genes on the Y chromosome Y-linked Genes: genes on the Y chromosome

6. Sex Linked Traits Most sex linked genes are found on the X chromosome Most sex linked genes are found on the X chromosome Only genes on the Y chromosome are for male reproductive organ development Only genes on the Y chromosome are for male reproductive organ development

7. Sex Linked Genetic Problems In flies: R = red eyes, r = white eyes In flies: R = red eyes, r = white eyes Gene located on the X chromosome Gene located on the X chromosome X X Y X

8. Example 1: White eye male mates with a red homozygous dominant female White eye male mates with a red homozygous dominant female X r Y x X R X R X r Y x X R X R XRXrXRXr XRYXRY XRXrXRXr XRYXRY XrXrXrXr Y XRXRXRXR XRXRXRXR 100 % red female 0 % white female 100 % red male 0 % white male

9. Example 2: Red eye male mates with a red heterozygous female Red eye male mates with a red heterozygous female X R Y x X R X r X R Y x X R X r XRXRXRXR XRYXRY XRXrXRXr XrYXrY XRXRXRXR Y XRXRXRXR XrXrXrXr 100 % red female 0 % white female 50 % red male 50 % white male

10. Example 3: White eye male mates with a red heterozygous female White eye male mates with a red heterozygous female X r Y x X R X r X r Y x X R X r XRXrXRXr XRYXRY XrXrXrXr XrYXrY XrXrXrXr Y XRXRXRXR XrXrXrXr 50 % red female 50 % white female 50 % red male 50 % white male

11. Linkage Groups Genes located on the same chromosome and therefore inherited together Genes located on the same chromosome and therefore inherited together Goes against Mendel’s Law of Independent Assortment Goes against Mendel’s Law of Independent Assortment

12. How do linked genes get “unlinked”? Crossing Over Crossing Over The frequency of crossing over between certain genes is used to make a chromosome map The frequency of crossing over between certain genes is used to make a chromosome map

13. Which two genes have the highest probability of crossing over? The lowest? Which two genes have the highest probability of crossing over? The lowest? A B C a b c Highest: A & C Lowest: A & B

14. Chromosome Map: Diagram of the linear order of genes on a chromosome

16. Sex Linkage Problems!!!! Use these genotypic symbols for the sex linked trait of red-green color blindness in humans to solve the problems that follow. "Normal" female = XBXB "Normal" female = XBXB Carrier female = XBXb Carrier female = XBXb Color-blind female = XbXb Color-blind female = XbXb Normal male = XBY Normal male = XBY Color-blind Male = XbY Color-blind Male = XbY

17. 1) A normal female marries a color blind male. What are the chances that the offspring will be color blind if they are females? What are the chances that the offspring will be color blind if they are males?

18. 2) A color blind female marries a normal male. How many of the female offspring will be carriers of the color blind allele?

19. 3) A man whose mother is color blind marries a woman with normal vision. What is the genotype of the husband? What percent of their offspring can be expected to be color blind? What percentage of their offspring can be expected to be carriers?

20. How do biologist keep track of inherited traits over generations in a family? Pedigree (page 241) Pedigree (page 241)

21. Pedigree Key Normal male Affected male Normal female Affected female Marriage Dead Let’s try a pedigree problem!

24. R = Tongue Roller r = No Tongue Roller John Jones, a tongue roller, marries Jill Smith, a woman that cannot roll her tongue. John and Jill have four children that can each roll their tongue: John Jr., Alice, Lisa, and Sean. John Jr. later marries non-tongue roller Pamela, and they have four children: Jessica, Sherri, Mary, and John III. Sherri and Mary both can roll their tongues, and Jessica and John III are non-tongue rollers. Sean marries Robin, a non- tongue roller. Both Robin’s parents are non- tongue rollers also. Sean and Robin have four children: Nicholas, Harry, Donna, and Sean Jr. Nicholas, Harry and Donna each have the ability to roll their tongues. Sean Jr. cannot.

25. Human Genetics Section 12.2

26. Human genetics is not as easy as Mendel’s peas! Many patterns of inheritance

27. Human Patterns of Inheritance 1. Single allele trait 2. Multiple allele trait 3. Polygenic trait 4. X-linked trait 5. Nondisjunction

28. 1. Single Allele Trait A trait that is controlled by a single allele of a gene A trait that is controlled by a single allele of a gene Normal dominant-recessive (Mendel) Normal dominant-recessive (Mendel) Example Genetic Disorders: Example Genetic Disorders: Huntington’s Disease (autosomal dominant) Huntington’s Disease (autosomal dominant) Cystic Fibrosis (autosomal recessive) Cystic Fibrosis (autosomal recessive)

29. 2. Multiple Allele Trait 3 or more alleles of the same gene code for a single trait 3 or more alleles of the same gene code for a single trait Example: ABO Blood Type Example: ABO Blood Type I A = type A (dominant) I B = type B (dominant) i = type O (recessive)

30. Blood Type Problems If a person is type A blood….what is his/her genotype? If a person is type A blood….what is his/her genotype? I A I A or I A i If a person is type B blood….what is his/her genotype? If a person is type B blood….what is his/her genotype? I B I B or I B i If a person is type O blood….what is his/her genotype? If a person is type O blood….what is his/her genotype?ii If a person is type AB blood….what is his/her genotype? If a person is type AB blood….what is his/her genotype? IAIBIAIBIAIBIAIB

31. Blood Types Blood Type (Phenotype) GenotypeCan donate blood to:Can receive blood from: OiiA,B,AB and O (universal donor) O ABIAIBIAIB A,B,AB and O (universal receiver) AI A I A or I A i AB, AO,A BI B I B or I B iAB,BO,B

32. Blood Type Problems # 1 A mother gives birth to a type O child. The mother is type A blood. The two potential fathers are type A (father 1) and type AB (father 2). A mother gives birth to a type O child. The mother is type A blood. The two potential fathers are type A (father 1) and type AB (father 2). Who’s the daddy? Who’s the daddy?

33. Blood Type Problems #2 Pretend that Mark is homozygous for blood type “A” allele, and Mary is type “O”. Pretend that Mark is homozygous for blood type “A” allele, and Mary is type “O”. What are all the possible blood types of their baby? What are all the possible blood types of their baby?

34. 3. Polygenic Trait Trait that is controlled by 2 or more genes Trait that is controlled by 2 or more genes Range of phenotypes Range of phenotypes Influenced by environmental factors too Influenced by environmental factors too Examples: Examples: skin color eye color human height

35. 4. X-Linked Trait Trait controlled by a gene on the X chromosome Trait controlled by a gene on the X chromosome Examples: Examples: colorblindness (recessive) hemophilia (recessive)

36. Hemophilia Pedigree

37. 5. Nondisjunction The failure of chromosomes to separate during meiosis resulting in one gamete with too many chromosomes and one gamete with too few chromosomes The failure of chromosomes to separate during meiosis resulting in one gamete with too many chromosomes and one gamete with too few chromosomes Trisomy Monosomy

38. Trisomy: cell with 3 copies of a chromosome (too many chromosomes) Trisomy: cell with 3 copies of a chromosome (too many chromosomes) Monosomy: cell with 1 copy of a chromosome (too few chromosome) Monosomy: cell with 1 copy of a chromosome (too few chromosome) Example Genetic Disorders: Example Genetic Disorders: Down Syndrome (Tri-21) Klinefelter’s Syndrome (XXY) Turner’s Syndrome (X__)

39. Blood Typing Lab! Background Background Blood is a tissue comprised of 4 components: plasma, red and white blood cells, and platelets. Plasma is a clear straw-colored liquid portion that makes up 55% of the blood. It contains a number of blood-clotting chemicals that help stop bleeding. Red and white blood cells and platelets make up the remaining 45% of the blood. Red blood cells are tiny biconcave discs. Each red blood cell contains the oxygen-binding protein, hemoglobin. Hemoglobin contains 4 iron ions with bind with oxygen and carbon dioxide.

40. Blood functions principally as a vehicle with transports gases, metabolic waste products and hormones throughout the body. As blood passes through the lungs, oxygen molecules attach to the hemoglobin. As blood passes through the body’s tissues in capillary beds, the hemoglobin releases the oxygen. Carbon dioxide and other waste gases are, in turn, transported by the hemoglobin back to the lungs. Thereafter the process is repeated. Blood functions principally as a vehicle with transports gases, metabolic waste products and hormones throughout the body. As blood passes through the lungs, oxygen molecules attach to the hemoglobin. As blood passes through the body’s tissues in capillary beds, the hemoglobin releases the oxygen. Carbon dioxide and other waste gases are, in turn, transported by the hemoglobin back to the lungs. Thereafter the process is repeated.

41. Mutations that Lead to Genetic Disorders: Mutation: a change in the DNA of an organism Mutation: a change in the DNA of an organism Can involve an entire chromosome or a single nucleotide Can involve an entire chromosome or a single nucleotide Can lead to genetic disorders Can lead to genetic disorders

43. Mutation Types 1. Germ-cell mutation: occurs in the germ cells (gametes) Does not affect the organism Does not affect the organism Does affect the organism’s offspring Does affect the organism’s offspring 2. Somatic-cell mutation: occurs in the organism’s body cells Does affect the organism Does affect the organism Does not affect the organism’s offspring Does not affect the organism’s offspring 3. Lethal mutation: causes death, often before birth

44. 4. Chromosome mutation: change in the structure of a chromosome a. Deletion – loss of a piece of chromosome b. Inversion- segments of chromosome breaks off, flips, and reattaches c. Translocation- piece of chromosome breaks off and attaches to another chromosome d. Nondisjunction- chromosome fails to separate during meiosis

45. Deletion Inversion NondisjunctionTranslocation

46. 5. Gene mutation: involves large segments of DNA or a single nucleotide of DNA a. Point mutation: single nucleotide mutation within a codon (substitution, addition, or deletion) b. Frame shift mutation: cause the misreading of codons during translation thus making the wrong protein (insertion or deletion)

48. Detecting Human Genetic Disorders Before Pregnancy: Before Pregnancy: 1. Genetic Screening 2. Genetic Counseling During Pregnancy: During Pregnancy: 1. Amniocentesis 2. Chorionic Villi Sampling After Birth: After Birth: 1. Genetic Screening video