Punnet Squares and Blood Types Mrs. McCarthy October 6, 2015October 6, 2015October 6, 2015

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 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%

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

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

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

Monohybrid Punnet Square Practice Step 3: Complete a punnett square Y y y y Yy Yy yy yy Step 4: List your final results by genotypes and phenotypes with the proper ratio GenotypePhenotype ½ Yy ½ Yellow ½ yy ½ Green

Monohybrid Punnet Square Practice Monohybrid Punnet Square Practice 2. Cross a heterozygous round seed plant with another heterozygous round seed plant. R= roundr= wrinkled Rr ● Rr Rr ● Rr R r R r RR Rr Rr rr GenotypePhenotype ¼ RR ¼ Round ½ Rr ½ Round ¼ rr ¼ wrinkled

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= Blackb= white BB ● bb BB ● bb B B b b Bb Bb Bb Bb GenotypePhenotype 4/4 Bb All Black

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= roundY= yellow r= wrinkled y=green Step 2: Show your cross RRyy ● rrYy Step 3: Show the different types of combinations in gametes. RRyyRyrrYyrY, ry

Dihybrid Punnet Square Practice Step 4: Show your punnet square rYry Ry RrYy Rryy Step 5: Show your genotypes and phenotypes GenotypePhenotype ½ RrYy ½ Round, Yellow ½ Rryy ½ Round, green

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 RRYy RrYy RRyy Rryy ry rY Rryy rryyrrYy RrYy GenotypePhenotype 1/8 RRYy 1/8 Round, Yellow 1/8 RRyy 1/8 Round, Yellow ¼ Rryy ¼ Round, green 1/8 rryy 1/8 wrinkled, green 1/8 rrYy 1/8 wrinkled, yellow ¼ RrYy ¼ Round, Yellow

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= I A I A or I A iB= I B I B or I B i O= iiAB= I A I B Cross the same as a regular monohybrid cross !

Blood Types 1. Cross a homozygous type A man with a type O woman. I A I A ● ii I A I A ● ii IAIA i i IAi IAi IAi IAi GenotypePhenotype 4/4 I A i All type A

Blood Types 2. Cross a heterozygous type A man with a heterozygous type B woman. I A i ● I B i IAIAIAIAi IBIBIBIB i IAIBIAIBIAIBIAIB IAiIAiIAiIAi IBiIBiIBiIBi ii GenotypePhenotype ¼ I A I B ¼ Type AB ¼ I A i ¼ type A ¼ I B i ¼ type B ¼ ii ¼ type O

Homework Complete Genetics Worksheet #1