F1 generation: The first set of offspring from the original parents being crossed. F2 generation: The second generation of offspring.

Transcription

1 Padon the Punnett By: Nancy Volk The Punnett Squae This module stems fom the wok of the Austian Monk, Gego Mendel, the fathe of genetics. In the mid-1800s Mendel studied the pattens of inheitance of physical chaacteistics of the gaden pea, and established the basic laws of genetics still ecognized today. Definitions: Gene: Section of a chomosome that caies the infomation fo a specific tait. Allele: Altenate foms of a gene. Genotype: The fundamental genetic makeup of an oganism fo a specific tait; the combination of the two alleles located on the homologous chomosomes that detemines the expession (phenotype) of the tait. The genotype is epesented by two lettes, which ae in uppe and lowe case to epesent diffeent alleles. Example: is genotype fo the dominant tait of a ound pea seed and is the genotype fo the ecessive tait of a winkled pea seed. Phenotype: The way a tait physically expesses itself in an oganism. Example: winkled seeds vs. smooth seeds, ed flowes vs. white flowes. Homozygous: The genotype has both lettes being exactly the same. This would be eithe both dominant genes o both ecessive genes. ( o ) Heteozygous: The genotype has a dominate gene and a ecessive gene fo the same tait. ( o Gg) Dominant Tait: A genetic tait is consideed dominant if it is expessed in an oganism who has only one copy of that gene. In genetic tems, a dominant tait is one that is phenotypically expessed in heteozygotes. Example: o is expessed as ound seeds. ecessive Tait: efes to an allele that causes a phenotype that is only seen in homozygous genotype and neve in a heteozygous genotype. If a genetic tait is ecessive, the oganism needs to inheit two copies of the gene fo the tait to be expessed. Thus, both paents must be caies of the tait in ode fo the offsping to expess that tait. Example: is expessed as a winkled seed Punnett s Squae: A mathematical tool that helps pedict the offsping outcome (both genotypes and phenotypes) of a coss between two paents with known genotypes. F1 geneation: The fist set of offsping fom the oiginal paents being cossed. F2 geneation: The second geneation of offsping. Pobability: The chance/possibility that a specific event will occu. Coss: Mating of two paent oganisms. Offsping: esults of a coss; young poduced by coss. VOCABULAY Adenine Amino acids Codons Complementay Cytosine DNA Guanine Mutation Nucleotide Poteins Thyamine Inside This Packet The Punnett Squae 1 New Yok State Standads 1 Activity: Using a Punnett Squae eview and Moe 4 New Yok State Standads Middle School Living Envionment Standad 1: Key Idea 1: 1.1a, 1.1b, 1.3a, 1.3b, 1.4a Key Idea 2: 2.3a, 2.3b Key Idea 3: 3.1a, 3.3 Standad 4: Key idea 2: 2.1a, 2.1b, 2.1c, 2.1e, 2.1j, 2.1k 2 Life Sciences - Pio Module 1 High School Page 1

2 Activity: Using a Punnett Squae MATEIALS NEEDED Student woksheet Steps to using the Punnett squae: 1) Identify the paents genotype. 2) Place the paents genotype at the top and left side of the boxes. 3) Combine the genotypes fo each box. Students should be able to: Undestand how to use and complete a Punnett squae. 4) Wite out the genotypes and phenotypes fo all offsping. Ty this! Example A: In the floweing plant called Scentilia (made up), the dominant tait is a ed flowe and the ecessive tait is a white flowe. The genotype fo one paent is homozygous dominant. This paent is cossed with a Scentilia plant that has a white flowe. Detemine the phenotypes and genotypes of the offsping. Solution A: Daw a Punnett squae: Step 1: Identify the paent genotypes: Homozygous Dominant = cossed with a white plant that must be homozygous ecessive () in ode to be a white flowe. Step 2: Place the paents genotypes in place to be cossed. Life Sciences - Pio Module 1 High School Page 2

3 Activity: Using a Punnett Squae Step 3: Combine the genotypes fo each box. Step 4: Wite out the genotypes and phenotypes fo all offsping Genotypes: 100% Phenotypes: 100% ed flowe Ty anothe! Example B: What ae the phenotypes and genotypes of the offsping of two heteozygous Scentilia plants who have ed flowes? Solution B: Daw a Punnett squae: Life Sciences - Pio Module 1 High School Page 3

4 Activity: Using a Punnett Squae Step 1: Identify the paent genotypes: Heteozygous means one dominant and one ecessive gene so each paent has a genotype of. Step 2: Place the paent s genotypes in place to be cossed. Step 3: Combine the genotypes fo each box. Step 4: Wite out the genotypes and phenotypes fo all offsping Genotypes: 25% homozygous dominant (), 50% heteozygous (), 25% homozygous ecessive () Phenotypes: 75% ed flowes and 25% white flowes Life Sciences - Pio Module 1 High School Page 4

5 Activity: Using a Punnett Squae Ty anothe! Ty the following examples: 1. Coss a shot pea plant with one that is homozygous fo tallness. The dominate tait is tallness and the ecessive tait is shotness. 2. What will the offsping be like fom the coss of a white hamste and a bown hamste if the bown hamste s mothe was white? White is ecessive and bown is the dominant tait. 3. ound pea seed is dominant and winkled ecessive. Coss two paents who have winkled seeds. Solution 1: Genotype: 100% heteozygous () Phenotype: 100% tall plants t T T t Solution 2: Genotype: 50% heteozygous (Bb) and 50% homozygous ecessive (bb) Phenotype: 50% bown and 50% white B b Bb b Bb b bb bb Solution 3: Genotype: 100% homozygous ecessive () Phenotype: 100% winkled seeds Life Sciences - Pio Module 1 High School Page 5

6 eview and Moe eview Questions 1. Which of the following is a possible abbeviation fo a genotype? A. BC B. Pp C. Ty D. fg 2. What is the best way to detemine the phenotype of the feathes on a bid? A. analyze the bid s DNA (genes) B. look at the bid s feathes C. look at the bid s beak d. examine the bid s doppings 3. Which of the following pais is not coect? A. kk = hybid B. hybid = heteozygous C. heteozygous = Hh D. homozygous = 4. The genes pesent in an oganism epesent the oganism s. A. genotype B. phenotype C. physical taits 5. Which statement is not tue? A. Genotype detemines phenotype. B. Phenotype detemines genotype. C. A phenotype is the physical appeaance of a tait in an oganism. D. Alleles ae diffeent foms of the same gene. 6. Make up you own Punnett poblem fo you classmates and show the solution below: Altenative Poject Ideas: 1) eseach the life of Gegoy Mendel and epot about his life wok to the class. 2) Develop a plan to coss seveal plants to tace the phenotype and genotypes of the offsping. Fom Baby Steps Though Punnett Squae by M. Kousen Go hee to lean moe about Mendel s Genetic Laws. Life Sciences - Pio Module 1 High School Page 6