1. Chapter 13 (Part 3) Non-Mendelian Genetics Honors Genetics Ms. Gaynor

2. Extending Mendelian Genetics for a Single Gene  The inheritance of characters by a single gene May deviate (do NOT follow) from simple Mendelian patterns Examples  Incomplete dominance, codominance, multiple alleles, pleiotropy

3. The Spectrum of Dominance  Complete dominance Occurs when the phenotypes of the heterozygote (Hh) and dominant homozygote (HH) are identical Demonstrates or follows “Mendelian Genetics” inheritance pattern

4. “Non-Mendelian Genetics” Incomplete (intermediate) Dominance  1 allele is not completely dominant over the other, so heterozygote (Hh) has intermediate (or mixed) phenotype between 2 alleles (like snapdragon flowers)

5. Figure 14.10 P Generation F 1 Generation F 2 Generation Red C R Gametes CRCR CWCW  White C W Pink C R C W Sperm CRCR CRCR CRCR CwCw CRCR CRCR Gametes 1⁄21⁄2 1⁄21⁄2 1⁄21⁄2 1⁄21⁄2 1⁄21⁄2 Eggs 1⁄21⁄2 C R C R C W C W C R C W

6. Let’s do some practice problems…  Assume incomplete dominance…  A red gummy bear mates with a yellow gummy bear. Red (R) is dominant. What are the genotype/phenotype ratios of their F1 offspring?  100% Rr 100% orange  If 2 F1 gummy bears from the question above mate. What are the genotype/phenotype ratios of their F2 offspring?  25% RR 50% Rr 25% rr  25% Red 50% orange 25% yellow

7. “Non-Mendelian Genetics” Codominance 2 dominant alleles affect phenotype in separate, distinguishable ways BOTH phenotypes are present  Ex’s of codominance Some flowers and Roan animals (cattle & horses)

8. Roan Animals Show Codominance

9. Let’s do some practice problems…  Assume codominance…  A blue flower mates with a yellow flower. Blue (B) is dominant. What are the genotype/phenotype ratios of their F1 offspring?  BB= blueBb= blue & yellowbb= yellow  100% Bb 100% Blue AND yellow flowers  If 2 F1 flowers from the question above mate. What are the genotype/phenotype ratios of their F2 offspring?  25% BB 50% Bb 25% bb  25% Blue 50% blue AND yellow 25% yellow

10. Multiple Alleles  A type of codominance  Most genes exist in populations In more than two allelic forms that influence gene’s phenotype  Ex: Human Blood type

11. The ABO blood group in humans Is determined by multiple alleles Table 14.2

12. Multiple Alleles (Codominance) Blood Type Genotypes AI A I A, or I A i BI B I B, or I B i ABIAIBIAIB Oii

14. Blood Type Practice A woman with Type O blood and a man, who is Type AB, are expecting a child. What are the possible blood types of their child? ii x I A I B  50% chance I A i (A type); 50% chance I B i (B type) What are the possible blood types of a child who's parents are both heterozygous for "B" blood type? I B i X I B i  50% chance I B i, 25% chance I B I B, 25% chance ii 75% chance of B type and 25% chance of O type

15. More Blood Type Practice What are the chances of a woman with Type AB and a man with Type A having a child with Type O? I A ? x I A I B  0% chance of Type O b/c mom can’t donate “i” allele Jill is blood Type O. She has two older brothers with blood types & B. What are the genotypes of her parents? I A i and I B i Jerry Springer did a test to determine the biological father of child The child's blood Type is A and the mother's is B. Daddy Drama #1 has a blood type of O & Daddy Drama #2 has blood type AB. Which man is the biological father? Dad #1 = ii and Dad #2= I A I B  It has to be Daddy #2

16. Polygenic Inheritance  Many genes (2+) determine one (1) phenotype  Many human traits Vary in the population along a continuum  Few genes actually follow a simple Mendelian inheritance pattern Examples:  Height, eye color, intelligence, body build and skin color

17. Polygenic Inheritance  AaBbCc aabbcc Aabbcc AaBbccAaBbCcAABbCc AABBCcAABBCC 20 ⁄ 64 15 ⁄ 64 6 ⁄ 64 1 ⁄ 64 Fraction of progeny

18. Nature and Nurture: The Environmental Impact on Phenotype  Departs from simple Mendelian genetics  phenotype depends on environment as well as on genotype  Called multifactorial inheritance Ex: human fingerprints hydrangea flowers Al in soil; need LOW pH Add P to soil; need HIGHERpH

19. Chapter 11 (Part 4) Human Genetics Honors Genetics Ms. Gaynor

20. Many human traits follow Mendelian patterns of inheritance  Humans are not convenient subjects for genetic research However, the study of human genetics continues to advance We use pedigrees !

21. Pedigree Analysis  A pedigree Is a family tree that describes the interrelationships of parents and children across generations

22. Inheritance patterns of particular traits can be traced and described using pedigrees Figure 14.14 A, B Ww ww Ww wwWw ww Ww WW or Ww ww First generation (grandparents) Second generation (parents plus aunts and uncles) Third generation (two sisters) Ff ffFf ff Ff ff Ff FF or Ff ff FF or Ff Widow’s peak No Widow’s peak Attached earlobe Free earlobe (a) Dominant trait (widow’s peak) (b) Recessive trait (attached earlobe)

26. Pedigrees Can also be used to make predictions about future offspring

27. Recessively Inherited Disorders  Many genetic disorders are inherited in recessive manner Show up only in individuals homozygous for the alleles  Carriers Are heterozygous individuals, who carry recessive allele but are show “normal” phenotype

28. Cystic Fibrosis  Example of recessive disorder  Affect mostly people of European descent  Symptoms Mucus buildup in the some internal organs Abnormal absorption of nutrients in the small intestine

29. Sickle-Cell Disease  Another recessive disorder Affects one out of 400 African-Americans Is caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells  Symptoms Physical weakness, pain, organ damage, and even paralysis

30. Dominantly Inherited Disorders  Some human disorders Are due to dominant alleles  Example is achondroplasia Form of dwarfism  lethal when homozygous for the dominant allele

31. Another Dominant Disorder  Huntington’s disease (HD) degenerative disease of nervous system No obvious phenotypic effects until about 35 to 40 years of age HD Normal

32. Down Syndrome  Down syndrome Is usually the result of an extra chromosome 21  trisomy 21

33. Genetic Testing and Counseling  Genetic counselors Can provide information to prospective parents concerned about a family history for a specific disease

34. Tests for Identifying Carriers  For a growing number of diseases Tests are available that identify carriers and help define the odds more accurately Examples  Tay Sachs & CF

35. Fetal Testing  In amniocentesis The liquid that bathes fetus is removed & tested  In chorionic villus sampling (CVS) A sample of the placenta is removed and tested Can make karyotypes, too!

36. Newborn Screening  Some genetic disorders can be detected at birth Simple tests are now routinely performed in most hospitals in the United States Example- PKU test

37. Chapter 13 (PART 5) The Chromosomal Basis of Inheritance Introduction to Sex Linkage Honors Genetics Ms. Gaynor

38. Gene Linkage  Linked genes Usually inherited together because located near each other on the SAME chromosome  Genes closer together on the same chromosome are more often inherited together  Each chromosome Has 100’s or 1000’s of genes  Sex-linked genes exhibit unique patterns of inheritance; genes on the X or Y chromosome

39. Morgan’s Experimental Evidence  Thomas Hunt Morgan Provided convincing evidence that chromosomes are the location of Mendel’s heritable alleles

40. Sex linkage explained  Thomas Hunt Morgan (Columbia University 1910)  Fruit Flies (Drosophila) melanogaster) http://nobelprize.org/nobel_prizes/medicine/articles/lewis/index.html © 2007 Paul Billiet ODWSODWS

41. Morgan’s Choice of Experimental Organism  Morgan worked with fruit flies Lots of offspring A new generation can be bred every two weeks They have only 5 pairs of chromosomes

42. Morgan and Fruit Flies  Morgan first observed and noted Wild type (most common) phenotypes that were common in the fly populations  Traits alternative to the wild type are called mutant phenotypes WILDTYPE MUTANT w+w+ w

43. The case of the white- eyed mutant CharacterTraits Eye colorRed eye (wild type) White eye (mutant) P Phenotypes Wild type (red-eyed) female x White-eyed male F 1 Phenotypes All red-eyed Red eye is dominant to white eye

44. Hypothesis A cross between the F 1 flies should give us: 3 red eye : 1 white eye F2F2 PhenotypesRed eyeWhite eye Numbers3470 82% 782 18% So far so good

45. An interesting observation F2F2 PhenotypesRed- eyed males Red- eyed females White- eyed males White- eyed females Numbers10112459782 0 24%58%18% 0% The F 2 generation showed the 3:1 red: white eye ratio, but only males had white eyes

46. A reciprocal cross Morgan tried the cross the other way round white-eyed female x red-eyed male Result All red-eyed females and all white- eyed males This confirmed what Morgan suspected The gene for eye color is linked to the X chromosome

47. Morgan’s Discovery: Sex Linked Traits  Eye color is linked on X Chromosome  Females carry 2 copies of gene; males have only 1 copy  If mutant allele is recessive, white eyed female has the trait on both X’s  White eyed male can not hide the trait since he has only one X.

48. The Chromosomal Basis of Sex  An organism’s sex Is an inherited phenotype determined by the presence or absence of certain chromosomes XX = girl XY = boy

49. Inheritance of Sex- Linked Genes  The sex chromosomes Have genes for many characters unrelated to sex (especially the X chromosome)  A gene located on either sex chromosome Is called a sex-linked gene (Usually on X chromosome)

50. What genes are on the X chromosome?  carries a couple thousand genes but few, if any, of these have anything to do directly with sex determination  Larger and more active than Y chromosome

51. What genes are on the Y chromosome?  Gene called SRY triggers testis development, which determines male sex characteristics  This gene is turned “on” ~6 weeks into the development of a male embryo  Y-Chromosome-linked diseases are rare

52. Sex-linked genes follow specific patterns of inheritance  Fathers  pass sex-linked alleles to ALL their daughters but NONE to their sons XY (Father)  XX (daughter) XY (Father)  XY (son)  Mothers  can pass sex-linked alleles to BOTH sons and daughters XX (Mother)  XX (daughter) XX (Mother)  XY (son)

53. Sex Linkage  If sex-linked recessive on X n Females have to be X n X n to show sex-linked trait X n X Females do NOT show sex- linked trait Males have to be X n Y to show sex- linked trait **Most sex-linked disorders affect males; sometimes females

54. Sex-Linked Disorders  Some recessive alleles found on the X chromosome in humans cause certain types of disorders Color blindness Duchenne muscular dystrophy Hemophilia Male pattern baldness

55. X-Linked Trait = Male Pattern Baldness Baldness

56. Another X-Linked Trait = Hemophilia  About 85% of hemophiliacs suffer from classic hemophilia 1 male in 10 000 cannot produce factor VIII  The rest show Christmas disease where they can’t make factor IX  The genes for both forms of hemophilia are sex linked  Hemophiliacs have trouble clotting their blood

57. Another X-Linked Trait = Red-Green Colorblindness Normal vision Color blind simulation http://www.onset.unsw.edu.au/issue1/colourblindness/colourblindness_print.htm

58. Another X-Linked Trait = Duchenne Muscular Dystrophy