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Ch. 11 Notes - Genetics

Ch. 11 Notes - Genetics. I. Who was Gregor Mendel?. A. Gregor Mendel - Austrian monk who studied how traits a re inherited ; known as the “ Father of Genetics ” 1. Genetics - branch of biology that studies heredity a. Heredity - passing on of traits from parent to offspring.

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Ch. 11 Notes - Genetics

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  1. Ch. 11 Notes - Genetics

  2. I. Who was Gregor Mendel? A. Gregor Mendel - Austrian monk who studied how traits are inherited; known as the “Father of Genetics” 1. Genetics - branch of biology that studies heredity a. Heredity- passing on of traits from parent to offspring

  3. I. Who was Gregor Mendel? B. Mendel’s Experiments 1. Studied/Researched on pea plants a. They have many traits such as flower color (purple or white), peas (round or wrinkled), pea color (yellow or green) and height (tall or short).

  4. I. Who was Gregor Mendel? P1 b. Mendel bred a tall pea plant with a short plant (P generation). c. The offspring in the 1st generation (F1 generation) were alltall. Short pea plant Tall pea plant F1 All tall pea plants F2 3 tall: 1 short

  5. I. Who was Gregor Mendel? P1 d. Then, he bred two of the F1 plants. e. The offspring in the 2nd generation (F2 generation) were 75% tall and 25% short. f. The short trait disappeared in the 1st generation and reappeared in the 2nd generation. Short pea plant Tall pea plant F1 All tall pea plants F2 3 tall: 1 short

  6. I. Who was Gregor Mendel? P1 2. Mendel discovered that each trait is controlled by alleles. a. Alleles: forms/versions of the same gene • Each person has TWO alleles for each gene; 1 from mother and 1 from father. • Ex: T = the allele for tall; t = the allele for short Short pea plant Tall pea plant F1 All tall pea plants F2 3 tall: 1 short

  7. I. Who was Gregor Mendel? • Some alleles are dominant and recessive • Dominant- a trait that is always expressed (seen) in an individual if the allele is present (capital letter) • Ex: T = tall allele • Recessive- a trait that is hidden by the dominant allele; expressed only when two copies of the recessive allele are inherited (lowercase letter) • Ex: t = short allele

  8. I. Who was Gregor Mendel? • Individuals can be described by their genotype and phenotype • Genotype - genetic makeup (letters); alleles present in an individual • Ex: TT, Tt, tt • Type of Genotypes: • Homozygous - two of the SAME alleles for a trait • Ex: TT or tt • Heterozygous (hybrid) - two DIFFERENT alleles for a trait • Ex: Tt

  9. I. Who was Gregor Mendel? • Phenotype - physical appearance; what traits are expressed in the individual • Ex: tall or short plants TT, Tt=tall tt=short

  10. II. Punnett Squares/Test Crosses A. Punnett Square/Test Cross- a tool used to predict the alleles/traits present in offspring 1. When parents produce gametes (sperm or eggs), their genes separate to produce haploid cells a. Each gamete contains ONE allele Homozygous Short Dad Heterozygous Tall Dad Homozygous Tall Dad t t T T T t

  11. II. Punnett Squares/Test Crosses B. How to Solve a Monohybrid Cross 1. Determine the genotypes (letters) of the parents. 2. Set up the punnettsquare with one parent on top and one parent on the side. 3. Fill out the Punnettsquare boxes (Look up and over to the left to fill them in). 4. Analyze the probability (likelihood) that the offspring would possess each specific trait.

  12. II. Punnett Squares/Test Crosses C. Practice Y = yellow pea color; y = green pea color 1. Cross two heterozygous pea plants. • Parent 1 Genotype __________ Parent 2 Genotype __________ • What is the chance of the offspring having yellow pea color? Genotypic Ratio: YY : Yy : yy Phenotypic Ratio: yellow : green

  13. II. Punnett Squares/Test Crosses Y = yellow pea color; y = green pea color 2. Cross a homozygous recessive pea plant with a heterozygous pea plant. • Parent 1 Genotype __________ Parent 2 Genotype __________ • What is the chance of the offspring having yellow pea color? Genotypic Ratio: YY : Yy : yy Phenotypic Ratio: yellow : green

  14. II. Punnett Squares/Test Crosses Y = yellow pea color; y = green pea color 3. Cross a homozygous recessive pea plant with a homozygous dominant pea plant. • Parent 1 Genotype __________ Parent 2 Genotype __________ • What is the chance of the offspring having yellow pea color? Genotypic Ratio: YY : Yy : yy Phenotypic Ratio: yellow : green

  15. II. Punnett Squares/Test Crosses D. How to Solve a Dihybrid Cross 1. Determine parent genotypes (letters). 2. Determine gamete combinations from mom and dad. (FOIL method from math class - Use arrows!) 3. Write the gametes from mom on 1 side of the square and dad on the other side. 4. Fill in the boxes in the punnett square (look up and to the left). 5. Analyze the probability (likelihood) that the offspring would possess the specific traits.

  16. II. Punnett Squares/Test Crosses PRACTICE: • R = round peas, r = wrinkled peas • Y = yellow pea color; y = green pea color • Cross two heterozygous round yellow pea plants. • Parent 1 Genotype _____ Parent 2 Genotype _____ • Parent Gamete Possibilities: FOIL Parent #1 Gametes: RY, Ry, rY, ry Parent #2 Gametes: RY, Ry, rY, ry

  17. Ry RY rY ry • What is the chance of the offspring having round and yellow peas? RY Ry rY ry

  18. III. Special Inheritance A. Autosomes- 22 pairs of body chromosomes in a human 22 Autosomes Sex chromosomes

  19. III. Special Inheritance B. Sex chromosomes- 1 pair of chromosomes in a human; the last pair in a karyotype a. Ex.XX-female XY-male 22 Autosomes Sex chromosomes

  20. III. Special Inheritance • Show a punnett square crossing male and female sex chromosomes. d. Every time a male and female have a baby, what is the chance of them having a son? A daughter? e. If a female has 5 sons in a row, what is the chance of her having another son? A daughter? f. Which parent determines the sex of the child? WHY?

  21. III. Special Inheritance C.Sex-Linked Traits - traits located on the sex chromosomes (usually the X chromosome) a. Dad gives X chromosome to daughters and Y chromosome to sons b. Mom gives X chromosome to daughters and sons • If a male inherits a sex-linked trait, which parent(s) gave him the trait? • MOM • If a female inherits a sex-linked trait, which parent(s) gave her the trait? • MOM OR DAD • Who (males or females) is most likely to inherit a sex-linked trait? WHY? • Males – they only need to inherit ONE X chromosome

  22. III. Special Inheritance c. Examples in humans • Male pattern baldness • Red/green colorblindness • Hemophilia (problems with blood clotting) • Muscular Dystrophy (muscle weakness, loss of muscle tissue)

  23. III. Special Inheritance d. Other Examples • Eye color in Drosophila (fruit flies) • R = Red eye Color; r = white eye color • Cross white eyed male (XrY) with red eyed female (XRXR) What percentage of offspring are likely to have red eyes? What percentage of male offspring are likely to have red eyes? What percentage of female offspring are likely to have red eyes?

  24. III. Special Inheritance • Examples • Eye color in Drosophila (fruit flies) • R = Red eye Color; r = white eye color • Cross white eyed male (XrY)& heterozygous red eyed female (XRXr) What percentage of offspring are likely to have red eyes? What percentage of male offspring are likely to have red eyes? What percentage of female offspring are likely to have red eyes?

  25. IV. Not all traits are controlled by simple dominant and recessive alleles! A. Incomplete Dominance - heterozygous individuals display an intermediate (blending) phenotype of the two homozygous individuals 1. Examples in humans • Hair texture • SS = straight • CC = curly • SC = wavy • Tay Sachs Disease (inability to produce enzyme that breaks down lipids) • EE = produces enzyme • NN = does not produce enzyme • EN = produces half amount of enzyme

  26. IV. Not all traits are controlled by simpledominant and recessive alleles! 2. Other Examples • Flower color in snapdragons • RR = Red, WW = white, RW = pink • Cross a red flower with a white flower. • Parent 1 Genotype ______ Parent 2 Genotype _____ • What is the chance of producing a pink flower? Genotypic Ratio: RR : RW : WW Phenotypic Ratio: red: pink: white

  27. III. Not all traits are controlled by simple dominant and recessive alleles! • Cross a pink flower with a pink flower. • Parent 1 Genotype _____ Parent 2 Genotype _____ • What is the chance of producing a white flower? Genotypic Ratio: RR : RW : WW Phenotypic Ratio: red: pink: white

  28. III. Not all traits are controlled by simple dominant and recessive alleles! B. Co-dominance - heterozygous individuals display BOTH traits of the two homozygous individuals 1. Examples in humans • Sickle Cell Anemia (abnormally shaped red blood cells) • NN = normal shaped cells • SS = sickle shaped cells • NS = normal and sickled shaped cells • Blood Type • Type A • Type B • Type AB

  29. ***** Special Inheritance ***** • Hemoglobin—protein that carries oxygen in blood, makes blood red • In homozygous recessive individuals—hemoglobin is defective and makes blood cells sickle (half moon) shaped • These blood cells—cause slow blood flow, block small vessels, tissue damage and pain • In heterozygous individuals – both normal and sickled hemoglobin are produced • They produce enoughnormal hemoglobin that they do not have serious health problems

  30. IV. Not all traits are controlled by simple dominant and recessive alleles! 2. Other Examples • Coat color in chickens • BB = black • WW = white • BW = black AND white speckled • Cross a black rooster with a white chicken. • Parent 1 Genotype _____ Parent 2 Genotype _____ • What is the chance of producing black and white chicks? Genotypic Ratio: BB: BW : WW Phenotypic Ratio: black: black/white: white

  31. IV. Not all traits are controlled by simple dominant and recessive alleles! Complete the last cross on your own. Be ready to discuss.

  32. V. Blood Type (codominance in humans) A. An example of multiple alleles – more than one allele controls the trait B. It is determined by the presence or absence of proteins (chains of amino acids) on the surface of red blood cells a. Mixing incompatible blood types can cause blood clots, which can result in death

  33. V. Blood Type (codominance in humans) • Human Blood Types

  34. V. Blood Type(codominance in humans)

  35. V. Blood Type (codominance in humans) C. Alleles IA and IB – are co-dominant to each other D. Allele i –is recessive to both IA and IB a. Type O blood — universal donor • Has no proteins on the blood cells so any blood type can receive it b. Type AB blood — universal acceptor • Has both proteins on blood cells so this blood type can receive any blood

  36. V. Blood Type (codominance in humans) E. Cross parent with A ( IAi) blood with a parent with B blood (IBi). Genotypic ratio 0 IAIA: 1 IAi : 0 IBIB : 1 IBi: 1 IA IB : 1 ii IA i IBi IAIB IB i ii IAi Phenotypic ratio (blood type)— 1 type AB : 1 type A : 1 type B : 1 type O

  37. VI. Rh Factor – describe the presence or absence of another protein on blood cells. A. Rh Positive = have proteins a. Genotypes: Rh+/Rh+ or Rh+/Rh- B. Rh Negative = no proteins b. Genotype: Rh-/Rh-

  38. VI. Rh Factor – describe the presence or absence of another protein on blood cells. C. Cross parent heterozygous for the Rh factor with another parent who does not have the Rh factor. Rh+ Rh- Rh- Rh- Rh+/Rh- Rh-/Rh- Rh-/Rh- Rh+/Rh- Phenotypic ratio 2 Rh positive: 2 Rh negative Genotypic ratio 0 Rh+/Rh+ : 2 Rh+/Rh-: 2 Rh-/Rh-

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