1. Genetic Crosses and
Pedigrees

2. Monohybrid Crosses
Meaning ONE trait

3. Activity
• Look at the following plant crosses.
• T = Tall t = Dwarf
1. 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)

4. 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

5. Worksheet
• Sponge Bob worksheet

6. Dihybrid Crosses
Meaning 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

7. AnswersDihybrid Crosses
Meaning TWO traits
• What are the two traits?
1.White or Brown colour fur
2. 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

8. Example
Question :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

9. Exercises
2. Textbook
Questions pg. 82 to 84

10. Pedigree Chart
• A diagram that shows the family relationships
and how characteristics are passed on from one
generation to the next.
Autosomal Dominant Pedigree Chart
Lets 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 .

11. Extra Online - Putting into Practise
• http://www.execulink.com/~ekimmel/mendel1a.htm
1. 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

12. Putting into Practise continued..• http://www.execulink.com/~ekimmel/mendel1a.htm
1. 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:
•
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 6
Girl or boy?
2. Genetics Work booklet – (See under teacher desk S4)
Questions pg. 82 to 84