Genetic Crosses and Pedigrees

Monohybrid CrossesMeaning ONE trait

Activity• Look at the following plant crosses.• T = Tall t = Dwarf1. a) What are the possible genotypes of the

parents if they are both homozygous for the trait?

b) Draw a monohybrid Cross for the parents. c) What are the genotypes and phenotypes

of the offspring (F1 )?2. One plant from the F1 generation is

crossed with a heterozygous Tall plant. a) Draw a monohybrid cross

b) What are the genotypes and phenotypes of the offspring (F2)

Answers Activity1. a) What are the possible genotypes of the parents if they are both

homozygous for the trait? TT and tt b) Draw a monohybrid Cross for the parents.

T T t

t

c) What are the genotypes and phenotypes of the offspring (F1) )Genotype = 100% Tt Phenotypes =100 % All Tall 2. a) One plant from the F1 generation is crossed with a heterozygous

Tall plant. T t a) Draw a monohybrid cross T

t

b) What are the genotypes and phenotypes of the offspring (F2)Genotypes: 25% TT, 50 %Tt, 25 % tt Phenotype = 75% Tall, 25% dwarf

Tt Tt

Tt Tt

TT Tt

Tt tt

Worksheet

• Sponge Bob worksheet

Dihybrid CrossesMeaning TWO traits

• What are the two traits?• What are the alleles for

these two traits?• What are the possible

phenotypes of this cross? Refer dihybrid cross

• What are all the possible genotypes for each trait this cross? Refer dihybrid cross

AnswersDihybrid CrossesMeaning TWO traits

• What are the two traits?1.White or Brown colour fur2. Long or short tail• What are the possible alleles for these traits?• Tail - SS, Ss, ss Fur Colour - BB, Bb, bb• What are the possible phenotypes of this

cross?Phenotypes – Brown / long tail, Brown / short tail, white / short tail, white / long tail

• What are the possible phenotypes of this cross?Genotypes - SSBB, SSBb, SSbb, SsBB, SsBb, Ssbb, ssBB , ssBb, ssbb

ExampleQuestion :1. Use the example above to draw your own Dihybrid Cross for:

Homozygous Wrinkled Homozygous yellow pea (rrYY)x

Heterozygous Round Homozygous green pea (Rryy)

rrYY rY rY rY rY

Ry

Rryy Ry

ry

ry

.

2.What are the possible genotypes of this cross?3.What are the possible phenotypes of this cross?

RrYy RrYy

Exercises

2. TextbookQuestions pg. 82 to 84

Pedigree Chart• A diagram that shows the family relationships and

how characteristics are passed on from one generation to the next.

Autosomal Dominant Pedigree ChartLets say alleles are G and g.

Label all the people in the pedigree with their genotypes.

If they are a carrier place a dot in the middle of the circle or square.

Phenotypes are already noted .

Extra Online - Putting into Practise• http://www.execulink.com/~ekimmel/mendel1a.htm1. See link above for an online activity on crosses and pedigrees. Students to

work through individually on laptops and CHECK answers as they go. Go to COMMON DRIVE and ACCESS this POWERPOINT

Steps: Go to the sight and complete the following:

Under title:1. More Genetics on this Website• Click and complete:

Drag-and-Drop Genetics (Internet Explorer only)

2. Java Genetics Full List • Problem 1

Monohybrid cross • Problem 2

Monohybrid cross • Problem 3

Blood type

Putting into Practise continued..• http://www.execulink.com/~ekimmel/mendel1a.htm1. See link above for an online activity on crosses and pedigrees. Students to work through individually on laptops and CHECK

answers as they go. Go to COMMON DRIVE and ACCESS this POWERPOINTSteps: Go to the sight and complete the following:

Under title:1. More Genetics on this Website• Click and complete:•

CyberStranded 3 Drag-and-Drop DNA Model (Tutorial Video) Drag-and-Drop DNA Model (Internet Explorer only)Drag-and-Drop Genetics (Internet Explorer only)Drag-and-Drop Pedigree (Internet Explorer only)Drag-and-Drop Pedigree (Flash version) Genetics: Blood Type (Tutorial Video) Genetics: Monohybrid Cross (Tutorial Video)

2. Java Genetics Full List • Problem 4

Dihybrid cross

• Problem 5"Dash" technique with blood type

• Problem 6Girl or boy?

2. Genetics Work booklet – (See under teacher desk S4)Questions pg. 82 to 84