Transcript How to work Pedigree Charts

Pedigree Charts
Quiz 7B
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.
Pea Plant Characteristics
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 T
Short t
Show a cross between a tall and
short pea plant
Step Two
Write down possible
genotypes and phenotypes.
Purebred dominant
hybrid
Purebred recessive
TT
Tall
Tt
Tall
tt
Short
Show a cross between a tall and
short pea plant
Step Three
Fill in the genotypes of the
parents on the pedigree chart.
Pedigree Chart
P1
P2
F1
Parents
TT
P1
tt
P2
In the circle - the possible gametes of
the female are listed.
In the square - the possible gametes of
the male are listed
Show a cross between a tall and
short pea plant
Step Four
Fill in the genetic possibilities
of the F1
on the pedigree chart.
Cross between a tall and short pea plant
TT
P1
tt
P2
Tt
F1
Take first gene from the female and first gene from
the male and place in the first offspring spot.
Cross between a tall and short pea plant
TT
P1
Tt
tt
P2
Tt
F1
Take first gene from the female and second gene from
the male and place in the second offspring spot.
Cross between a tall and short pea plant
TT
tt
P1
Tt
P2
Tt
Tt
F1
Take second gene from the female and first gene from
the male and place in the third offspring spot.
Cross between a tall and short pea plant
TT
tt
P1
Tt
P2
Tt
Tt
Tt
F1
Take second gene from the female and second gene
from the male and place in the fourth offspring spot.
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
Cross between a tall and short pea plant
TT
tt
P1
Tt
0:4:0
4:0
P2
Tt
Genotypic Ratio
Phenotypic Ratio
Tt
Tt
F1