Pedigree Charts

1
Pedigree Charts

• Quiz 7B

2
Pedigree Charts

• Besides showing possible gene pairings, a
  pedigree chart gives the probability of each
  pairing.
• It shows how often, on the average, a given
  pairing will occur.

3
Pea Plant Characteristics
4
Show a cross between a tall and short pea plant
Step One
Write down the set of contrasting traits.
Assign the capitol letter to the dominant trait
and the lower case letter to the recessive trait.
Tall Short
T t
5
Show a cross between a tall and short pea plant
Step Two
Write down possible genotypes and phenotypes.
TT Tt tt
Tall Tall Short
Purebred dominant
hybrid
Purebred recessive
6
Show a cross between a tall and short pea plant
Step Three
Fill in the genotypes of the parents on the
pedigree chart.
7
Pedigree Chart
P1
P2
F1
8
Parents
tt
TT
P1
P2
In the circle - the possible gametes of the
female are listed. In the square - the possible
gametes of the male are listed
9
Show a cross between a tall and short pea plant
Step Four
Fill in the genetic possibilities of the F1 on
the pedigree chart.
10
Cross between a tall and short pea plant
tt
TT
P1
P2
Tt
F1
Take first gene from the female and first gene
from the male and place in the first offspring
spot.
11
Cross between a tall and short pea plant
tt
TT
P1
P2
Tt
Tt
F1
Take first gene from the female and second gene
from the male and place in the second offspring
spot.
12
Cross between a tall and short pea plant
tt
TT
P1
P2
Tt
Tt
Tt
F1
Take second gene from the female and first gene
from the male and place in the third offspring
spot.
13
Cross between a tall and short pea plant
tt
TT
P1
P2
Tt
Tt
Tt
Tt
F1
Take second gene from the female and second gene
from the male and place in the fourth offspring
spot.
14
Show a cross between a tall and short pea plant
Step Five
Write down the genotypic ratio and the phenotypic
ratio.
Purebred dominant Hybrid Purebred recessive
Dominant Recessive
15
Cross between a tall and short pea plant
tt
TT
P1
P2
Tt
Tt
Tt
Tt
F1
040
Genotypic Ratio
40
Phenotypic Ratio