1. Genetics – the study of heredity

2. What is heredity? Because we know that offspring look like their parents, it stands to reason that the information on how to develop is passed from parent to offspring.

3. Heredity is the passing of genetic information from one generation to the next. How does genetic information get passed from parent to offspring?

4. HISTORY OFGENETICS The first person to scientifically study heredity was GREGOR MENDEL. He was a well-educated Austrian monk who studied garden plants in the 1850’s.

5. He was interested in HOW traits get passed from parent to offspring. Mendel is best known for his work with 1000’S of garden pea plants.

6. Mendel chose pea plants to study Because pea plants reproduce quickly so he could get lots of data. Pea plant traits occur in only two forms which made them easy to observe. EX: Plants were either tall or short, flowers were either white or purple. WHY PEA PLANTS?

7. Mendel could allow plants to self- pollinate or he could easily cross- pollinate them.

8. Cross Pollination – the transfer of pollen of one flower to the stigma of another flower. Pollen – powdery substances that produces male sex cells Stigma – receptacle for pollen, transfers pollen to ovule or egg.

9. STOP AND REVIEW 1. What is genetics? 2. What is heredity?

10. REVIEW 3. Who was Gregor Mendel? 4. What country was he from? 5. During what time period did he study heredity? 6. Why did Mendel study pea plants? 7. What is cross pollination?

11. MENDEL’S OBSERVATIONS Mendel noticed that some plants always produced tall plants and others always produced short plants. Mendel used these PUREBREDS to start his experiments.

12. A PUREBRED organism is onethat always produces offspring with the same form of a trait as the parent. Example: A purebred tall plant crossed with another purebred tall plant always produces tall plants.

13. MENDEL’S FAMOUS EXPERIMENTS He wondered….. What offspring would be produced if he crossed a purebred tall plant with a purebred short plant? What do you think he hypothesized?

14. MENDEL’S FAMOUS EXPERIMENT – Mendel decided to cross a purebred TALL plant with a purebred SHORT plant. SURPRISINGLY….. – All of the first generation (F 1 generation) offspring were TALL. Where had the short trait gone? Had it disappeared? Called the F1 generation (means first filial generation or the first generation after the parents.)

15. But when he crossed the first generation plants (F 1 X F 1 ) their offspring or the 2 nd generation (F 2 ) were both TALL and SHORT. The short trait reappeared!

16. MORE EXPERIMENTS Mendel repeated this experiment over and over and every time the F2 generation produced 3 tall plants and 1 short plant or a 3 to 1 ratio. He reasoned that there must be two factors that control the trait.

17. Mendel conducted similar experiments with other pea traits such as seed shape, seed color, pod color, flower color, etc.

18. STOP AND REVIEW 1. What did Mendel first observe about some tall and some short plants? 2. What is a purebred plant?

19. REVIEW 3. What offspring resulted when Mendel crossed purebred tall with purebred short plants? 4. What happened when he crossed the F1 generation plants?

20. MENDEL’S CONCLUSIONS The results of Mendel’s experiments led him to conclude that: a.One heredity factor comes from each parent for a trait. b.Heredity factors are inherited in pairs.

21. Mendel’s Conclusions c.One factor can “cover up” or mask the other factor. The factor that covered up the other he called: DOMINANT The factor being covered up he called: RECESSIVE

22. About Mendel… His studies were ignored during his day but years later scientists discovered his work, repeated his experiments and confirmed his results.

23. He lived out his life without knowing that these factors were “genes "on chromosomes, and died without receiving recognition for his great contribution to science.

24. Mendel’s careful, thorough, scientific studies and accurate results earned him the title of “Father of Genetics.

25. Traits controlled by only one pair of heredity factors are now referred to as a Mendelian traits. A Mendelian trait is one that is controlled by a single pair of genes and shows a simple Mendelian inheritance pattern of being dominant and/or recessive.pair

26. STOP AND REVIEW 1.What other pea plant traits did Mendel use for his experiments? 2.What 3 things did Mendel conclude? 3.What does it mean when one trait is dominant over the other? 4. Did Mendel know he was called the “Father of Genetics? Why or why not?

27. GENETICS TODAY Mendel’s factors today are called: Genes: sections of a chromosome or DNA that codes for a trait. We inherit 23 pairs of homologous chromosomes, one from each parent, which have genes for the same traits.

29. In pea plants each trait has two variations. These variations or forms of a trait are called ALLELES. Example: In pea plants: The trait: height of plant The two alleles: tall or short TRAITS HAVE VARIATIONS - ALLELES

30. Pea Plant Traits and Alleles TraitFlower Color Seed Color Seed Shape Pod color Pod Shape Flower Position Plant Height Dominant Alleles Recessive Alleles

31. Alleles can be DOMINANT OR RECESSIVE. -In pea plants: the tall allele is dominant the short allele is recessive. The two alleles work together to control the trait. DOMINANT AND RECESSIVE ALLELES

33. For example, the gene for flower color in pea plants has two alleles: PURPLE and WHITE Since purple is dominant to white, the flower will be purple.

34. Scientists use LETTERS to represent alleles. Dominant allele: Capital letter Recessive allele: Lower Case letter An organism inherits a gene from each parent for a trait so the alleles are written in pairs. Two letters are used to represent the pair of alleles for the trait. GENETIC SYMBOLS

35. EXAMPLE Peas will inherit two alleles for height. The letter chosen to represent the allele is the first letter of the dominant trait. Tall is dominant so a “T” is chosen. Only one letter is used for both traits. T = tall and t =short The letters are combined to represent the inherited allele pair. Possible combinations are: TT Tt tt

36. PRACTICE WITH SYMBOLS To determine the allele pairs for pea plant flower color: Look at chart to determine dominant trait. Purple = dominant White = recessive So choose letter “P”: PP or Pp or pp What are allele pair combinations for seed color? _________ _________ ________

37. GENETIC TERMS DOMINANT ALLELES exhibit their effect if they are present on at least ONE gene. TT = tall Tt – tall RECESSIVE ALLELES can only express their effect if they are on BOTH genes. tt = short

38. The letters represent the organism’s GENOTYPE for a trait. GENOTYPE – Inherited Allele pair A genotype shows the two alleles the organism inherited. Example: TT, Tt, tt GENOTYPE = GENE INFORMATION

39. GENOTYPE produces a PHENOTYPE A phenotype is the physical appearance of the trait resulting from the genotype or inherited allele pair. Example: tall results from TT. PHENOTYPE = PHYSICAL

41. GENOTYPEPHENOTYPE PPPurple flowers PpPurple flowers ppWhite flowers In pea plants purple flowers are dominant over white flowers.

42. GENOTYPEPHENOTYPE For the trait of eye color in humans, brown eyes are dominant over blue eyes.

43. PUREBRED (true breeding) organism always produces offspring with the same trait as the parent. PUREBRED OR HOMOZYGOUS

44. Purebreds have the same two alleles for a trait. Ex: TT – purebred tall tt – purebred short PURBRED = HOMOZYGOUS

45. HYBRID organism that has two DIFFERENT alleles for a trait. can produce offspring with either form of a trait Ex: Tt = hybrid tall HYBRID = HETEROZYGOUS HYBRID OR HETEROZYGOUS

47. GENETICS TERMS TermDefinitionGenotypePhenotype Homozygous Or Purebred Having two identical alleles for a trait TT tt Tall plant Short plant Heterozygous Or Hybrid Having two different alleles for a trait TtTall Plant

48. Pea plant alleles for seed color Yellow seed color: dominant Green seed color: recessive GenotypeResulting PhenotypeHeterozygous or Homozygous

49. Just to review… 35. An organism’s GENOTYPE tells what is actually in its DNA The PHENOTYPE describes the actual observable physical characteristics that result from the DNA.

50. PUNNETT SQUARES In 1905, Reginald Punnett developed a tool for predicting characteristics of offspring for traits with dominant and recessive alleles.

51. Punnett Square. A chart that shows all possible allele combinations that can occur in the offspring of a cross between two organisms. Used to PREDICT the PROBABILITY of a particular trait appearing in offspring. It does NOT show the ACTUAL outcome of a cross.

52. Probability Probability: the likelihood an event will occur. 0ne event does not affect the next one. Ex: Each time you flip a coin the chances of getting heads is always 50%. – The larger the sample, the more likely outcome will occur like prediction. Scientists use probability to predict the outcome of genetic crosses.

53. The chances of the trait appearing can be expressed as percentages or ratios PercentagesRatios 25% = 1 out of 4 = 1 to 3, 1:3 50% = 2 out of 4 = 2 to 2, 2:2 75% = 3 out of 4 = 3 to1, 3:1 100% = 4 out of 4 = 4 to 0, 4:0

54. How to Use a Punnett Square Predict the possible offspring from a purebred tall pea plant and a hybrid pea plant. The parents genotypes are TT and Tt.

55. Step 1: Identify Allele Pair for Parents What are the possible allele pairs that the offspring would inherit for eye color? Male: heterozygous brown Female: homozygous recessive blue Brown eyes are dominant. Blue eyes are recessive. Cross these two parents: BbX bb Step 2: Complete Punnett Square

57. Step 3 - Identify Probabilities of the Possible Offspring. Genotypes: Bb = 50% or 2 to 2 bb = 50% or 2 to 2 Phenotypes: Brown eyes = 50% Blue eyes = 50%

58. Problem: What are the possible offspring from a heterozygous yellow seed plant and a homozygous yellow seed plant? Step 1: Identify allele pairs Yellow pea seeds are dominant to green seeds: Allele for dominant trait: _________ Allele for recessive trait: _________ Allele pairs for parents: ________ X ________

59. Step 2:Complete Punnett Square Step 3: Identify Probabilities Probabilities Genotypes:__________________ Phenotypes:__________________

60. Green pods are dominant to yellow pods in pea plants. Green = ______ Yellow = _____ Predict the offspring of these parents : hybrid green pod x purebred yellow pod _________ x _________ Predictions:

61. Stopped here in 2012

63. Punnett Square: Cross of male and female to determine probability of having a male or female child. Probability of a male or female offspring 2 out of 4 or 50%

64. HUMAN TRAITS 26. Human traits also are determined by paired alleles in DNA. 27. Dominant traits are always observed in the phenotype or appearance if present. T-tall (dominant) t-short (recessive) TT=tall Tt=tall tt=short 28. Recessive traits are only seen if no dominant allele is present.

65. Human chromosomes

66. Human Female Karyotype showing 23 matched pairs of chromosomes

67. Human Male Karyotype- Chromosome pair 23 is unmatched.

68. 29. Human traits that are inherited in dominant and recessive allele pairs include these…

71. Some other human genetic traits….

72. Some bird genetic traits…

73. 30. Some traits are determined by MULTIPLE ALLELES… For example, blood type is determined by at least three alleles… 31. Other traits such as height and skin color are controlled not by multiple alleles, but by multiple genes!

74. 32. Some traits are not INHERITED but rather are acquired or developed due to the environment. 33. For example, a weight lifter gains large muscles from lifting weights, not necessarily from genes. 34. A child may grow to be a short adult even though he has genes for tallness because poor nutrition did not provide the nutrients to achieve the potential height.

75. Sources Tall x Short Pea Plants www.mysciencebox.org/files/images/tall%20shor... 221 x 351 - 13k Pea plants-tall and short library.thinkquest.org Pea flower http://www.sciam.com/article.cfm?chanId=sa003&articleId=F4604E0F-E7F2-99DF-30C88C9489BD83A2 Pea plants pollination diagram kentsimmons.uwinnipeg.ca/cm1504/Image216.gif Chromatids to Chromosomes 2/12/08 www.carolguze.com/text/442-1-humangenome.shtml Microscope Chromosome 2/11/08 http://fig.cox.miami.edu/~cmallery/150/mendel/heredity.htm Chromosome with Flower Color Allele 2/12/08 http://rds.yahoo.com/_ylt=A0WTb_kbD7JHTZAAiROjzbkF/SIG=123fu1jq1/EXP=1202938011/**http%3A// www.bio.miami.edu/dana/104/104F02_9.html http://rds.yahoo.com/_ylt=A0WTb_kbD7JHTZAAiROjzbkF/SIG=123fu1jq1/EXP=1202938011/**http%3A// www.bio.miami.edu/dana/104/104F02_9.html Flowers with Dominant-Recessive Alleles 2/12/08 www.brown.edu http://rds.yahoo.com/_ylt=A0WTefh_KrJHUycAyCejzbkF/SIG=12c9rtisb/EXP=1202945023/**http%3A//ww w.brown.edu/Courses/BI0032/gentherp/genIB2.html Pea plants with F generations marked 2/12/08 academic.kellogg.cc.mi.us/.../images/13_10.jpg Punnett square with flowers 2/13/08 http://en.wikipedia.org/wiki/User:Madeleine_Price_Ball/Genetics

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