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Punnet Squares and Blood Types

Punnet Squares and Blood Types. Mrs. McCarthy October 15, 2014. I. Punnett Square- helpful way of showing results from any cross Ex. If a purebred tall pea plant is crossed with a purebred short pea plant, the Punnett Square will show the probability of the offspring from this cross

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Punnet Squares and Blood Types

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  1. Punnet Squares and Blood Types Mrs. McCarthy October 15, 2014

  2. I. Punnett Square- helpful way of showing results from any cross Ex. If a purebred tall pea plant is crossed with a purebred short pea plant, the Punnett Square will show the probability of the offspring from this cross A. Probability- chance of how often something will occur, often written in a percent B. Ratio- numerical expression showing the relationship between two occurrences Ex. 1:2 or 50% or 1/2 3:4 or 75% or 3/4 Note: Like fractions, ratios should ALWAYS be written in its lowest form. Ex. 2:6 should be written as 1:3 or 33%

  3. II. Review: A. Monohybrid cross- a cross that involves one pair of contrasting traits B. Dihybrid cross- a cross that involves two pairs of contrasting traits

  4. III. How a Punnett Square Works A. Punnett squares are written using the alleles in the genotype TT Tt T t T T 1. Remember the law of segregation! The alleles separate during meiosis. Each gamete gets only ONE allele!

  5. IV. Monohybrid Punnett Square Practice Monohybrid crosses: 1. In peas, yellow seeds are dominant to green seeds. Cross a heterozygous yellow plant with a homozygous recessive (green) plant. Step 1: Write out genotype and phenotypes: Y=yellow y=green Step 2: Write out cross: Yy ● yy

  6. Monohybrid Punnet Square Practice y Y Step 3: Complete a punnett square y Yy yy y Yy yy Step 4: List your final results by genotypes and phenotypes with the proper ratio

  7. Monohybrid Punnet Square Practice 2. Cross a heterozygous round seed plant with another heterozygous round seed plant. R= round r= wrinkled Rr ● Rr r R R RR Rr r Rr rr

  8. Monohybrid Punnet Square Practice 3. In guinea pigs, black fur is dominant to white fur. Cross a homozygous dominant parent with a homozygous recessive parent. B= Black b= white BB ● bb B B b Bb Bb b Bb Bb

  9. V. Dihybrid Punnett Square Practice Dihybrid Cross: 1. Cross a homozygous round, green pea with a wrinkled, heterozygous yellow pea. Step 1: Write out genotype and phenotype R= round Y= yellow r= wrinkled y=green Step 2: Show your cross RRyy ● rrYy Step 3: Show the different types of combinations in gametes. RRyy Ry rrYy rY, ry

  10. Dihybrid Punnet Square Practice Step 4: Show your punnet square rY ry Ry Rryy RrYy Step 5: Show your genotypes and phenotypes

  11. Dihybrid punnet square practice 2. Cross a heterozygous round, yellow plant with a heterozygous round, green plant. R= Round Y=Yellow r= wrinkled y= green RrYy ● Rryy Gametes=RY, Ry, ry, rY and Ry, ry Ry ry RY rY Ry RRYy RRyy Rryy RrYy ry RrYy rryy rrYy Rryy

  12. VI. Blood Types A. Co-dominance- two dominant alleles are expressed at the same time Ex. Type AB blood B. Multiple Alleles- genes with three or more alleles Ex. Blood Types C. Blood Type Alleles: A= IAIA or IAi B= IBIB or IBi O= ii AB= IAIB Cross the same as a regular monohybrid cross!

  13. Blood Types • Cross a homozygous type A man with a type O woman. IAIA ● ii IA IA i IAi IAi i IAi IAi

  14. Blood Types 2. Cross a heterozygous type A man with a heterozygous type B woman. IAi ● IBi IA i IB IAIB IBi i IAi ii

  15. Homework Complete Genetics Worksheet #1

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