Gregor Mendel Genes & Alleles Genotype & Phenotype Homozygous & Heterozygous Punnett Square

1. Key to Heredity Gregor Mendel Genes & Alleles Genotype & Phenotype Homozygous & Heterozygous Punnett Square

2. Engage • What is the difference between acquired and inherited traits?

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4. What is heredity? • Passing of traits from parent to offspring or from one generation to the next. How are our traits determined? • Genesencode the instructions that define our traits. • Environmental factorsinfluence the expression of these genes.

5. How are genes inherited? • Humans have 2 sets of chromosomes for a total of 46 chromosomes. Each parent contributes only 1 set of chromosomes to their child. • When a sperm cell (23 chromosomes) and an egg cell (23 chromosomes) join during fertilization, it results in a zygote … a fertilized egg with 46 chromosomes.

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7. What is a trait? • Notable feature or quality in a person. What are the two types of traits? • Physical traitsare characteristics of one’s physical makeup. Ex. Eye color • Behavioral traitscharacteristics of the way one acts. Ex. Fetching behavior of golden retrievers.

8. How are genes inherited? • Gene =Trait.. From the DNA code Alleles. Different forms of the same trait • Parents can only give one allele for each trait to their offspring.

9. Father of Genetics = Gregor Mendel Show the film clip entitled The Genetic Work of Gregor Mendel (04:31) from the United Streaming film “Understanding Genetics”

10. Gregor Mendel • Austrian monk • Did his experiments in 1866 • He did plant experiments using the garden pea plant because they reproduce fast and have lots of visible traits. • He discovered the pattern in which organisms inherit traits

11. What traits did Mendel study?

12. GENE Mendel's Key Terms The factors that carry all traits = ALLELES Two different forms of the same gene =

13. How did Mendel control his experiments? • Cross pollinated pea plants • Kept individual plants from self-pollinating • Kept accurate data • Repeated his experiments to increase validity

14. First Experiment P1 generation (parental generation) F1 generation (first generation) Describe the results. 100% Purple

15. Second Experiment F1 generation (filial generation) F2 generation: (second generation) Describe the results. 75% Purple and 25% White

16. Mendel’s Law of Heredity • Law of Complete Dominance: when there is a dominant allele and a recessive allele inherited together for a particular gene, the dominant allele will be expressed. R Red r Dominant Red hair allele Recessive Blonde hair allele Express the dominant allele for red hair

17. DOMINANT T RECESSIVE t Mendel's Key Terms Allele that is expressed over another and represented by a capital letter Allele that is usually masked or appears less in the population and represented by a lowercase letter

18. When both alleles are theSAMEit is called When the alleles areDIFFERENTit is called RR Rr rr homozygous for Red hair heterozygous for Red hair homozygous for Blonde hair Mendel's Key Terms R = Red hair r = Blonde hair HOMOZYGOUS HETEROZYGOUS

19. HYBRID- Same thing as a heterozygous • Yy • Purebred – same thing as Homozygous • YY or AA • yy or aa • Aa

20. Paternal Maternal

21. PHENOTYPE – physical characteristics that you SEE Ex. Straight hair, red hair, freckles, lactose intolerant, tall, blue eyes Mendel's Key Terms You inherit two alleles for each gene (trait).1 from MOM! 1 from DAD! • GENOTYPE – genetic makeup represented by letters • Ex. RR, Tt, Ffgg, YyEePp

22. Gene Locus – location of specific gene Alleles – two forms of the same gene Genes on Chromosomes

23. Reginald Punnett • (1875-1967) • In 1902, created the Punnett Square- a chart which helped to determine the probable results of a genetic cross http://vector.cshl.org/dnaftb/concept_5/con5bio.html

24. Punnett Square3.each parent can only contribute one allele per gene4.these genes are found on the chromosomes carried in the sex cells.5.offspring will inherit 2 alleles to express that gene Male gametes T t T T T T t t T t t t Female gametes

25. BT Bt BbTt sperm bT haploid (n) diploid (2n) bt meiosis II Mendel’s 2nd Law of InheritanceLaw of Independent Assortment: the factors assort independently during gamete formation, giving different traits an equal opportunity of occurring together.

26. Mendel’s 3rd Law of Inheritance B sperm BB B BBbb haploid (n) b diploid (2n) bb b meiosis I meiosis II Law of Segregation: during the production of gametes the two copies of each hereditary factor segregate so that offspring acquire- 1 from each parent.

27. Punnett Squares COMPLETE DOMINANCE - one allele is dominant to another allele Steps to Solve Punnett Squares Step 1: Assign letters for alleles (use a letter that have obvious capital and lower case letters) Step 2: Write down the cross by determining the genotypes of the parents? Step 3: Set up and solve the Punnett square. Step 4: Answer questions, find ratios, percentages or proportions.

28. P P p p Punnett Squares COMPLETE DOMINANCE- one allele is dominant to another allele RECALL MENDEL’S 1st EXPERIMENTS CROSS: Purebred purple male x White female P1 generation = PP x ppMale gametes Female gametes Genotypic ratio = _______________ F1 generation Phenotypic ratio = ______________ Pp Pp Pp Pp 1Pp 1 purple

29. P p P p Punnett Squares RECALL MENDEL’S 2nd EXPERIMENT CROSS: Two F1 generation offspring with each other. F1 generation = Pp x PpMale gametes Female gametes Genotypic ratio = ____________________ F2 generation Phenotypic ratio = ____________________ PP Pp Pp pp 1PP:2Pp:1pp 3 purple:1 white

30. Male gametes B b B b Female gametes Monohybrid Crosses Cross two Alaskan huskies that areheterozygousforbrown eyes (Bb). STEP  BB = brown eyes Bb = brown eyes bb = blue eyes Genotypes % 25% BB, 50% Bb, 25% bb Ratios 1BB:2Bb:1bb STEP  BB Bb Cross Bb x Bb STEP  STEP  Bb bb Phenotypes % 75% Brown eyed, 25% Blue eyed Ratio 3 Brown eyed: 1 Blue eyed

31. T t T TT Tt t Tt tt Height in Pea plants Step 1: T = Tall t = short Step 2:Cross : Tt X Tt Step 3: Step 4: Genotypic Ratio: 1TT: 2Tt: 1tt Phenotypic Ratio: 3Tall: 1 short

32. F f F = purple f = white Cross: Ff X ff f Ff ff f Ff ff Flower color in pea plants Genotypic ratio: 1 Ff : 1 ff Phenotypic ratio: 1 purple: 1 white

33. Independent Assortment Experiment • Purple flowers (A) is dominant to white flowers (a) • Axial stems (B) are dominant to terminal stems (b)

34. Sickle Cell Anemia • most common inherited blood disorder in the United States • 1/500 African Americans • episodes of pain, chronic hemolytic anemia and severe infections, usually beginning in early childhood • high rates associated with zones of high malaria incidence, since carriers are somewhat protected against malaria.

35. Sickle Cell Anemia 2 individuals that have the sickle cell trait have children. Step 1: A = normal; a = sickle cell Step 2:Cross : Aa X Aa Step 3: Step 4: Genotypic Ratio: 1AA: 2Aa: 1aa Phenotypic Ratio: 3 normal: 1 sickle cell disease

36. Click on the “ Animation” button and listen to the tutorial for each section online. • Click on the “Problem” button to access the problem set for each section online. TUTORIALS

37. Genetics Part II Up until now… we have studied Gregor Mendel’s Laws of CompleteDominance. This is when there are only 2 phenoytpes. An organism either has the trait or doesn’t. Today… we will examine when those rules don’t apply in the Punnett Squares.

38. INCOMPLETE DOMINANCE- heterozygous genotype is a BLEND of both of the homozygous dominant and homozygous recessive allelesThink INTERMEDIATE phase

39. R W R RR RW W RW WW Snapdragon flower color RR = red RW = pink WW = white Cross: RW xRW Genotypic ratio: 1 RR: 2 RW : 1WW Phenotypic ratio: 1 red: 2 pink: 1 white

40. R W R W RR RW RW WW Coat color of cows RR = black RW = roan (brownish) WW = white Cross: RW X RW Genotypic ratio: 1 RR: 2 RW : 1 WW Phenotypic ratio: 1 black: 2 roan : 1 White

41. CODOMINANCE - BOTH alleles are equally expressed. Think Co-captains on a team… you see them both on the field.

42. B W B BB BW W BW WW Chicken feather color BB =Black BW = Black & white WW = white Cross: BW X BW Genotypic ratio: 1 BB: 2 BW: 1 WW Phenotypic ratio: 1 BLACK : 2 BLACK & WHITE: 1 WHITE

43. Polygenic Traits…..- when multiple genes are interacting to produce a phenotype ex. Eye color, heighthair color

44. SEX-LINKED TRAITS - gene is carried on the sex chromosomes • 1905, Nettie Stevens discovered that not every chromosome has a matching chromosome pair • normal diploid cell contains 46 chromosomes (2 sets of chr.) • gamete haploid cell contains 23 chromosomes (1 set chr.) • Autosomes = 1st22 pairs of chromosomes • Sex chromosomes = last 23rdpair of mismatched chromosomes • XX = femaleXY = male

45. Xr Y XR XR Xr XR Y Xr Xr Xr Xr Y Eyecolor in fruit flies – Drosophila melanogaster XR =red eyesXr= white eyes Cross: X r YxX R X r Genotypic ratio: 1 XR Xr : 1 XR Y: 1 XrXr: 1 Xr Y Phenotypic ratio: 1 red-eyed female: 1 red-eyed male: 1 white-eyed female: 1 white-eyed male

46. XN XN y y XN XN Xn Xn Male Pattern Baldness Sex-linked recessive XN XN XN y XN Xn Xny N = normal n = Bald

47. Colorblindness Sex-linked recessive http://www.toledo-bend.com/colorblind/Ishihara.html

48. XC Y XC XC XC XC Y Xc XC Xc Xc Y Colorblindness in Humans XC = normal eyes Xc= colorblind Cross: X C YxX C X c Genotypic ratio: 1 XC XC: 1 XC Y: 1 XC Xc: 1 Xc Y Phenotypic ratio: 2 normal females: 1 normal male: 1 colorblind male

49. Now,,, explain why males have these “diseases” more often than females… Males only have one X chromosome, so if they have the gene, they have the disease or trait…. They don’t have another X chromosome to “Mask” it

50. Males only have one X chromosome… so they do not have another to “mask” the defective gene.