1. Genes and Chromosomes

2. Thomas Morgan’s DISCOVERY of LINKED GENES Characteristics of linked genes 1.WHEN GENES ARE CLOSE TOGETHER ON A CHROMOSOME THEY TEND TO BE INHERITED TOGETHER 2.LINKED GENES tend to not SEPARATE from one another during Crossing Over Prophase I During Crossing Over in Prophase, they tend to stay together instead of separating and switching

3. How Morgan Discovered Linked Genes USED DROSOPHILA (Fruit Flies) WHY would he use fruit flies? They Mature in 2 weeks They Produce large numbers of offspring They only have 4 pairs of chromosomes One pair are the Sex CHROMOSOMES

4. The Experiment for Linked Genes Part I Thomas crossed PURE BRED fruit flies for two traits Homozygous Dominant GRAY BODIES & NORMAL WING SIZE (GGWW) with Homozygous Recessive flies that had BLACK BODIES & SMALL WINGS (ggww) GG WW X gg ww WHAT Genotype DID HE EXPECT IN THE OFFSPRING? GgWw WHICH IS WHAT HAPPENED Okay Big deal! What do you think he did next?

5. MORGAN’S Experiment Part II He then crossed an F-1 of the GgWw hybrid offspring w/a recessive ggww What would you expect? Fill out this punnett-  he did not get as expected… ¼ GRAY NORMAL ¼ GRAY SHORT ¼ BLACK NORMAL ¼ BLACK SHORT INSTEAD, he got… GgWw x ggww GWgwGwgW gw

6. Experiment’s Results for Part II 2300 total offspring Expected Actual Results Gg Ww alleles gg ww alleles

7. MORGAN’S RESULTS http://nortonbooks.com/college/biology/animations/ch11a01.htm http://nortonbooks.com/college/biology/animations/ch11a01.htm 41.5% GRAY body/Normal wings 41.5% BLACK body/small wings 8.5% GRAY body/Small wings 8.5% BLACK body/Normal wings MORGAN’s Conclusion The genes for wing size and body color were so commonly inherited as only two combinations either gray body/normal wing or black body/small wing that they had to be … on the same chromosome! This indicated that the genes for body color and wing size were… LINKED onto one chromosome.

8. Crossing Over Explains the other 8.5% combinations of either Black Body/Normal Wing or Gray body/Small Wing Chromosome combinations for gametes Homologous chromosomes

9. They can sometimes separate from one another during Crossing Over in Meiosis THIS MEANS THAT EVEN THOUGH GENES CAN BE LINKED,

10. Short Arm Long Arm Bands Represent Genes Cross-over Used to Map Genes

11. GENE MAP If you know the frequency of how often genes cross over, you can use the percentage to estimate how far apart the genes are from one another on a chromosome This is called a Gene Map So if two genes have an 8% frequency of crossing then are they far apart or close on a chromosome?

12. NETTIE STEVENS Discovered Sex Chromosomes She worked with MEALWORMS DISCOVERED they had 20 chromosomes. MALES had 19 regular size & 1 small one. The Females all the same size chromosomes SHE SAID “THE 19 that were the same are AUTOSOMES (body chromosomes), & the other set were SEX CHROMOSOMES” FRUIT FLIES same for male/females Males have XY Females have XX

13. GENES ON SEX CHROMOSOMES A gene located on a A SEX CHROMOSOME is called a SEX-LINKED GENE MORGAN DISCOVERED the 1 ST SEX-LINKED gene in fruit flies He crossed a PUREBRED Dominant RED-EYED FEMALE W + W + with a PUREBRED recessive WHITE- EYED WW MALE Let’s take a look at the 1 st cross.

14. Morgan’s 1 st Sex Linked Cross All offspring had red eyes

15. MORGAN’S 2 nd CROSS HE crossed from the F-1 generation a heterozygous FEMALE, W + W RED-EYED with a RED-EYED W + MALE (note only 1 allele! ) Let’s do the cross HE got a 3:1 RATIO of Red eye to White eye, but only MALES had WHITE EYES! Why? Since no FEMALES had WHITE EYES Morgan hypothesized that EYE COLOR must be a SEX-LINKED gene IT must be on the X CHROMOSOME The Y chromosome does not carry a gene for EYE COLOR The RECESSIVE TRAIT White eyes, is inherited more often in males that receive the r allele on their one and only X CHROMOSOME

16. MORGAN’S EXPERIMENTAL CROSS White eyed male Red eyed female All males had red eyes All females had red eyes 3:1 ratio red eyes to white eyes Only males had white eyes

17. Mutations Gene mutations – chemical change that affects the DNA molecule of a specific gene during DNA replication Chromosomal mutation – change in the number or the structure of chromosomes during meiosis

18. JOSEPH KOLREUTER 1760-Crossed white rr x red RR carnations He got…Rr which were pink! Phenotype was in between the parents He crossed the Rr hybrid F-1 and got red, white and pink combos This shows that R is incompletely dominant over the r gene r does not code for a protein but R can not compensate for this so an intermediate hybrid is created

19. INCOMPLETE DOMINANCE A PHENOTYPE THAT IS INTER-MEDIATE OF EITHER GENE

20. CODOMINANCE Two genes are expressed equally ONE gene is not DOMINANT over the other gene Two dominant genes Are expressed How does this happen?

21. POLYGENIC INHERITANCE INHERITANCE OF SEVERAL GENES TO EXPRESS A SINGLE TRAIT LIKE SKIN COLOR

22. Concept map scientists in this chapter

23. GENES AND HEREDITY Part 2!

24. Sickle Cell Anemia - A Codominant Disorder Red blood cells carry oxygen to all parts of your body. A protein called hemoglobin found in the red blood cell carries the oxygen. A person who has Sickle Cell Anemia has a gene which codes for defective hemoglobin.

25. Sickle Cell Anemia: A Codominant Disorder The red blood cell is normally disk shaped. When the body is lacking oxygen (exercise, anxiety) the red blood cells of a person with this disease become sickle shaped. The sickle shaped red blood cells get stuck in the capillaries (narrow blood vessels). Causes damage to the body. Can result in injury or death.

26. Sickle Cell Anemia - Genetics The allele for normal hemoglobin H A is codominant with the sickle cell allele H S. H A H S  Carriers suffer some of the effects of the disease. H S H S  People who are homozygous suffer from the full effects of the disease.

27. Sickle Cell Anemia- Fun Fact People who are Heterozygous for sickle cell anemia are resistant to a disease called Malaria. Malaria affects red blood cells. Malaria is spread by some mosquitoes found in tropical climates.

28. Polygenic Inheritance Polygenic Inheritance – The effect of two or more genes on a single phenotype. Example Skin color is controlled by three separate genes and combinations of these three genes give different skin tones. The amount of a pigment called Melanin determines how dark skin is. AABBCC = very dark aabbcc = very light AaBbCc = intermediate shade Example Weight and height is also controlled by several different genes.

29. Polygenic Inheritance Height is the result of many genes

30. Environmental Impact of Phenotype Phenotype depends on the environment as well as genes. Example Leaves on a tree vary in size, shape and greenness depending on their exposure to the wind and the sun. Example For humans, nutrition influences height, exercise alters build, and sun tanning darkens skin. Example Identical twins who are genetically identical accumulate phenotype differences as a result of their own unique experiences.

31. BLOOD TYPES CODOMINANCE/COMPLETE DOMINANCE

32. Blood Types A person can have the following blood types. A, B, AB or O Antigens - Carbohydrates on the surface of the cell determine what blood type you have.

33. Blood Types Multiple Alleles – A gene that has three or more alleles. (Example: Blood type) The blood groups result from combinations of the three alleles. The blood group alleles are symbolized I A (for A) I B (for B) i (for neither A or B). I A and I B are dominant to i. I A and I B together are codominant.

34. Blood Types

35. Blood Types - Matching antibodies = Proteins which attack foreign cells. Mixing the wrong blood groups will cause the antibodies to attack the foreign blood cells and cause them to clump up. (Agglutination)

36. Blood Types

37. AB is considered a universal recipient.

38. Blood Types O is considered a universal donor.

39. Blood Types

40. Blood Types - Rh Red blood cells have another antigen on their surface called the Rh antigen. Rh+ is dominant and Rh- is recessive. Rh+ genotypes Rh+ Rh+ Rh- Rh+ Rh- genotypes Rh- Rh-

41. Blood Types - Rh Rh+ has the Rh antigen and cannot develop Rh antibodies Rh+ can receive both Rh+ and Rh- blood types.

42. Blood Types - Rh Rh- do not have the Rh antigen and can develop Rh antibodies Rh- can only receive Rh- blood types.

43. What does pedigree mean? Pedigree: a diagram that traces one trait through several generations of a family X

44. = female= male

45. Example #1 How many girls? ___ How many boys? ___ momdad son daughter #1 3 2 daughter #2

46. momdad oldestyoungest son daughter #1daughter #2

47. A horizontal line connecting two shapes represents a cross/marriage. momdad

48. Example #2 How many crosses/marriages? 2 AB CDE F G

49. A vertical line extending down from a marriage/cross represents that the couple has children. momdad

50. AB CDE F G questions…

51. Example #3 How many couples have children? 4 AB CDEF H GH KJL MNO PRQST ?

52. AB CDEF How do you show twins?

53. How do you show traits? Shading RRRr mutation rr **A pedigree chart follows one trait. ( shaded = recessive )

54. Rr mom RR dad Rr son Rr daughter RrRr R RR Rr RR daughter R = tongue roller r = non-roller

55. AB CDEF H GH KJL MNO PRQST Practice questions…

56. What is wrong with this pedigree chart? This offspring cannot receive 2 recessive genes. This offspring cannot receive 2 dominant genes.

57. What are possible genotypes for individual W? W RrRr R r RRRr rr W could be RR (no shading) or Rr (half-shaded) or rr (all shaded).

58. Pedigree charts help to trace genetic diseases. Most genetic diseases are a recessive gene. If you have 1 recessive, you are a carrier, but you are not sick. If you have 2 recessive genes, you are sick with the disease. (you are “affected”) Aa aa Info to help you with page 93

59. 4 3 Granddaughter, carrier, 3 rd generation, older sibling Grandson, carrier, 3 rd generation, middle sibling 1 7 rr Rr

60. A person that carries one copy of the disease gene, but it is masked by the dominant trait. (hybrid) 2 U U is further left. This makes U older than V