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Understanding Punnett Squares: Calculating Seed Shape and Fur Color Genetics

This guide explains how to use Punnett squares to predict genetic outcomes for traits like seed shape (round vs. wrinkled) and fur color (black vs. white). It covers the genotypes RR (round), Rr (round), and rr (wrinkled) for seed shape, along with their corresponding phenotypes. The document also explains phenotypic ratios and genotypic combinations through practical examples, such as breeding dogs with heterozygous and homozygous traits, revealing the probability of offspring traits. Learn essential genetic concepts to enhance your understanding of inheritance.

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Understanding Punnett Squares: Calculating Seed Shape and Fur Color Genetics

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  1. TOPIC: GeneticsAim: Describe how to use punnett squares.Do Now: For the seed shape trait “R” represents round and “r” represents wrinkled. Give the genotypes and phenotypes for the three following gene combinations: RR, Rr, and rrHW: Activity: I’m all Keyed Up – DUE WEDNESDAY

  2. The phenotype of an organism a. represents its genetic composition b. reflects all the traits that are actually expressed c. occurs only in dominant pure organisms d. cannot be seen

  3. If an individual possesses two recessive alleles for the same trait, the individual is said to be a. homozygous for the trait             b. haploid for the trait c. heterozygous for the trait           d. mutated

  4. Probability • The possibility that an event may or may not happen

  5. 1/4 = 25% 2/4 = 50% 3/4 = 75% 4/4 = 100%

  6. Punnett Square • Special chart that shows possible gene combinations of offspring bw 2 organisms

  7. T T Example: 1. T = tall t = short TT x tt t t T t T T t t T t

  8. T T T t t T t t T t T t Phenotype= • 100% tall Genotype= 100% heterozygous

  9. B b 2. B = Black fur b = white fur Bb x Bb B B B B b b B b b b

  10. B b B b B B B b B b b b Phenotype= 75% black, 25 % white Genotype= 25% homozygous dominant 25% homozygous recessive 50% heterozygous

  11. Red is dominant in flowers & white is recessive. Cross a heterozygous flower with a homozygous dominant flower. • R = redr = white • Rr x RR

  12. Rr x RR R r Phenotype= R r R R R 100%red R R R R r Genotype = 50% homozygous dominant 50% heterozygous

  13. One dog carries heterozygous, black fur traits, and the other carries homozygous recessive white traits. What are the chances of having a puppy with black fur? B = black, b = white Bb x bb

  14. B b Bb x bb b b b B b Answer: 50% chance of having a puppy with black fur b B b b b

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