1 / 13

Punnett Squares

Punnett Squares. Step by step how to guide. Putting it together. Alleles represented by letters Capital letters = dominant (T) Lowercase letters = recessive (t) Two letters combined = trait TT, Tt, tt One from mom and one from dad Homozygous = both letters same TT or tt

marcel
Download Presentation

Punnett Squares

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Punnett Squares Step by step how to guide

  2. Putting it together • Alleles represented by letters • Capital letters = dominant (T) • Lowercase letters = recessive (t) • Two letters combined = trait • TT, Tt, tt • One from mom and one from dad • Homozygous = both letters same • TT or tt • Heterozygous = both letters differ • Tt

  3. Punnett Squares • A diagram that shows all possible outcomes of a genetic cross • Can be used to predict probabilities • Phenotype – an observable trait • Tall or short • Genotype – genetic make-up or combination of alleles • TT Tt tt

  4. Initial Steps (for a monohybrid cross) 1. Identify the Parents being used in the cross • Homozygous or heterozygous • TT, Tt, tt? • Most important step! 2. Segregate the alleles in each set of genes for each parent • Show meiosis creating the haploid cells

  5. Parent: (P) Tt x Tt Heterozygous Tall crossed with Heterozygous Tall Segregation of alleles: T t T t x Draw the Square: T t T Place the parents: t

  6. T t T T T T t T t t t t

  7. Tt x Tt What’s next? Ratios T t Genotypic Ratio: Ratio of allele combinations T T T T t TT = Tt = tt = 1 2 1 1:2:1 t T t t t Phenotypic Ratio: 3 1 3:1 Tall = Short = Ratio of traits

  8. Examples for you to work out! • Tt x tt -be sure to show both types of ratios • Cross a homozygous tall plant with a short plant -be sure to show both types of ratios

  9. Initial Steps (for a dihybrid cross) 1. Identify the Parents being used in the cross and figure out the combo of both traits. • Homozygous or heterozygous • TTGG, TTGg, TTgg, TtGG, TtGg, Ttgg, ttGG, ttGg, ttgg? • Most important step! 2. Segregate the alleles in each set of genes for each parent • Show meiosis creating the haploid cells

  10. Heterozygous Tall, Heterozygous Green plantcrossed with Heterozygous Tall, Heterozygous Green plant TtGg x TtGg TG Tg tG tg TG Tg tG tg x

  11. TtGg x TtGg Step 3 – Set up and complete the Punnett Square TG Tg tg tG TG T T G G T T G T G G T G t t g g Tg T T T G T T T G t t g g g g g g tG T G G T G G G G t t t t t t g g tg T G T G t t t t t t g g g g g g

  12. Phenotypic Ratio 9 Tall/Green: 3 Tall/yellow: 3 Short/Green: 1 Short /Yellow: 9:3:3:1 Phenotypic Ratio:

  13. Examples for you to work out! • Cross a heterozygous tall, yellow plant with a homozygous tall, heterozygous green plant. • Cross a heterozygous tall, yellow plant with a short, heterozygous green plant.

More Related