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

Punnet Squares and Punnet Squares and Blood TypesBlood Types

Mrs. McCarthyMrs. McCarthy

April 21, 2023April 21, 2023

I. Punnett Square- I. Punnett Square- helpful way of showing results from helpful way of showing results from any crossany crossEx. If a purebred tall pea plant is crossed with a purebred short pea plant, the Ex. If a purebred tall pea plant is crossed with a purebred short pea plant, the Punnett Square will show Punnett Square will show the probabilitythe probability of the offspring from this cross of the offspring from this cross

A. Probability- A. Probability- chance of how often something will chance of how often something will occur, often written in a percentoccur, often written in a percent

B. Ratio- B. Ratio- numerical expression showing the numerical expression showing the relationship between two occurrencesrelationship between two occurrences

Ex. Ex. 1:21:2 or or 50% 50% or or 1/21/2 3:43:4 or or 75% 75% oror 3/4 3/4

Note: Like fractions, ratios should Note: Like fractions, ratios should ALWAYSALWAYS be be written in its lowest form. written in its lowest form.

Ex. 2:6 should be written as Ex. 2:6 should be written as 1:3 or 33%1:3 or 33%

II. Review:II. Review:

A. Monohybrid cross- A. Monohybrid cross- a cross that involves a cross that involves one pair of contrasting traitsone pair of contrasting traits

B. Dihybrid cross- B. Dihybrid cross- a cross that involves a cross that involves two pairs of contrasting traitstwo pairs of contrasting traits

III. How a Punnett Square WorksIII. How a Punnett Square Works

A. Punnett squares are written using the A. Punnett squares are written using the alleles in the genotypealleles in the genotype

TTTT TtTt

TT TT TT tt

1. Remember the law of segregation! The alleles separate during meiosis. Each gamete gets only ONE allele!

IV. Monohybrid Punnett Square IV. Monohybrid Punnett Square PracticePractice

Monohybrid crosses:Monohybrid crosses:

1. In peas, yellow seeds are dominant to green 1. In peas, yellow seeds are dominant to green seeds. Cross a heterozygous yellow plant with a seeds. Cross a heterozygous yellow plant with a homozygous recessive (green) plant.homozygous recessive (green) plant.

Step 1: Step 1: Write out genotype and phenotypes: Write out genotype and phenotypes: Y=yellow Y=yellow y=greeny=green

Step 2: Step 2: Write out cross: Yy Write out cross: Yy ●● yy yy

Monohybrid Punnet Square Monohybrid Punnet Square PracticePractice

Step 3: Step 3: Complete a Complete a punnett punnett squaresquare

YY yy

yy

yy

YyYy

YyYy

yyyy

yyyy

Step 4: Step 4: List your final results by genotypes and List your final results by genotypes and phenotypes with the proper ratiophenotypes with the proper ratio

GenotypeGenotype PhenotypePhenotype

½ Yy½ Yy ½ Yellow½ Yellow

½ yy½ yy ½ Green½ Green


2. Cross a heterozygous round seed plant with 2. Cross a heterozygous round seed plant with another heterozygous round seed plant. another heterozygous round seed plant.

R= roundR= round r= wrinkledr= wrinkled

Rr ● RrRr ● Rr

RR rr

RR

rr

RRRR

RrRr

RrRr

rrrr


¼ RR¼ RR ¼ Round¼ Round

½ Rr½ Rr ½ Round½ Round

¼ rr¼ rr ¼ wrinkled¼ wrinkled


3. In guinea pigs, black fur is dominant to white fur. 3. In guinea pigs, black fur is dominant to white fur. Cross a homozygous dominant parent with a Cross a homozygous dominant parent with a homozygous recessive parent.homozygous recessive parent.

B= BlackB= Black b= whiteb= white

BB ● bbBB ● bb

BB BB

bb

bb

BbBb

BbBb

BbBb

BbBb


4/4 Bb4/4 Bb All BlackAll Black

V. Dihybrid Punnett Square V. Dihybrid Punnett Square PracticePractice

Dihybrid Cross: Dihybrid Cross: 1. Cross a homozygous round, green pea with a wrinkled, 1. Cross a homozygous round, green pea with a wrinkled,

heterozygous yellow pea.heterozygous yellow pea.Step 1: Step 1: Write out genotype and phenotypeWrite out genotype and phenotype

R= roundR= round Y= yellowY= yellowr= wrinkledr= wrinkled y=green y=green

Step 2: Step 2: Show your crossShow your crossRRyy ● rrYyRRyy ● rrYy

Step 3: Step 3: Show the different types of combinations in Show the different types of combinations in gametes.gametes.

RRyyRRyy RyRy rrYyrrYy rY, ryrY, ry

Dihybrid Punnet Square PracticeDihybrid Punnet Square Practice

Step 4: Step 4: Show your punnet squareShow your punnet square

rYrY ryry

RyRy RrYyRrYy RryyRryy

Step 5: Step 5: Show your genotypes and phenotypesShow your genotypes and phenotypesGenotypeGenotype PhenotypePhenotype

½ RrYy½ RrYy ½ Round, Yellow½ Round, Yellow

½ Rryy½ Rryy ½ Round, green½ Round, green

Dihybrid punnet square practiceDihybrid punnet square practice

2. Cross a heterozygous round, yellow plant with a heterozygous 2. Cross a heterozygous round, yellow plant with a heterozygous round, green plant.round, green plant.

R= Round Y=YellowR= Round Y=Yellowr= wrinkled y= greenr= wrinkled y= green

RrYy ● RryyRrYy ● RryyGametes=RY, Ry, ry, rY and Ry, ryGametes=RY, Ry, ry, rY and Ry, ry

RYRY RyRy

RyRy

ryry

RRYyRRYy

RrYyRrYy

RRyyRRyy

RryyRryy

ryry rYrY

RryyRryy

rryyrryy rrYyrrYy

RrYyRrYy


1/8 RRYy1/8 RRYy 1/8 Round, 1/8 Round, YellowYellow

1/8 RRyy1/8 RRyy 1/8 Round, 1/8 Round, YellowYellow

¼ Rryy¼ Rryy ¼ Round, ¼ Round, greengreen

1/8 rryy1/8 rryy 1/8 wrinkled, 1/8 wrinkled, greengreen

1/8 rrYy1/8 rrYy 1/8 wrinkled, 1/8 wrinkled, yellowyellow

¼ RrYy¼ RrYy ¼ Round, ¼ Round, YellowYellow

VI. Blood TypesVI. Blood Types

A. Co-dominance- A. Co-dominance- two dominant alleles are expressed at the two dominant alleles are expressed at the same timesame time

Ex. Ex. Type AB bloodType AB blood

B. Multiple Alleles- B. Multiple Alleles- genes with three or more allelesgenes with three or more allelesEx. Ex. Blood TypesBlood Types

C. Blood Type Alleles:C. Blood Type Alleles:A= A= IIAAIIAA or I or IAAii B= B= IIBBIIBB or I or IBBiiO= O= iiii AB= AB= IIAAIIBB

Cross the same as a regular monohybrid crossCross the same as a regular monohybrid cross!!

Blood TypesBlood Types

1.1. Cross a homozygous type A man with a type Cross a homozygous type A man with a type O woman.O woman.

IIAAIIA A ● ii● ii

IIAA IIAA

ii

ii

IIAAii

IIAAii

IIAAii

IIAAii


4/4 I4/4 IAAii All type AAll type A

Blood TypesBlood Types

2. Cross a heterozygous type A man with a 2. Cross a heterozygous type A man with a heterozygous type B woman.heterozygous type B woman.

IIAAi ● Ii ● IBBii

IIAA ii

IIBB

ii

IIAAIIBB

IIAAii

IIBBii

iiii


¼ I¼ IAAIIBB ¼ Type AB¼ Type AB

¼ I¼ IAAii ¼ type A¼ type A

¼ I¼ IBBii ¼ type B¼ type B

¼ ii¼ ii

¼ type O¼ type O

HomeworkHomework

Complete Genetics Worksheet #1Complete Genetics Worksheet #1

Documents

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