Warm ups: Match the following
terms to their definitions
1. genetics
2. trait
3. hybrid
4. gene
5. allele
6. Punnett square
7. haploid
8. meiosis
a. form of a gene
b. process of reduction division
c. specific characteristic
d. produced by crossing parents
with different alleles
e. containing a single set of
chromosomes
f. factor that controls traits
h. diagram showing possible gene
combinations
i. branch of biology that studies heredity
How to track traits in a family through the generations!
What is a Pedigree?
A pedigree is a chart of the genetic history of a family
over several generations.
1.
-
Can be used to determine genotypes of family members.
Can be used to help predict probability of future
generations expressing certain traits.
2. Important tool for genetic counselors
- they will use pedigree charts to help
determine
the distribution of a disease in an affected family
Constructing a Pedigree:
What do all these symbols mean?
Female – circle
 Male - square
- unshaded – does not show trait
- shaded – trait
- half shaded – carries the trait
- diagon slash = deceased
Connecting Pedigree Symbols
 Married Couple (mating)
- Straight line depicts
parents
 Children are connected
under the parents with a
vertical line
 Siblings are connected by
lines a horizontal under
the parents
Oldest child  Youngest child
Connecting Pedigree Symbols
Fraternal twins
Identical twins
Organizing the pedigree chart
 A pedigree chart of a family showing 20 individuals
 Generations are identified by Roman numerals
I
II
III
IV
Organizing the pedigree chart
I
Married couple
Their 5 children
Married couple
II
Married couple
Their 3 children
III
Married
couple
Married
couple
IV
Their 5 children
1.
2.
3.
List the people in the family that have the trait of blond hair.
List all the females in the family.
What relationship is person O to H? What relationship is person B to H?
A
C
J
K
D
L
E
B
F
G
H
I
P
O
M
Q
R
Answers;
1. E, Q, R
2. B, D, E, I, K,
M, P, Q, R
3. O is H’s son
B is H’s mom
S
T
U
Organizing the pedigree chart
 Scientists identify individuals in each generation by Arabic
numerals numbered from the left and the
 Therefore the affected individuals are II3, IV2 and IV3(instead of
letters)
I
II
III
IV
1.
2.
3.
4.
How many generations is this pedigree showing?
List the people in the family that have the trait of blue eyes.
List all the males in the family.
What relationship is person III2 toII3? What relationship is person I1 to II3?
Answers;
1. 3 generations
2. I1, III1
3. I1, II1, II3,
4. III2 is II3’s
daughter; I1 is II3’s
dad
Exit slip: Answer the following
questions
What is a pedigree?
2. What is the symbol for a male who has the trait?
3. What is the symbol for a female who doesn’t have the
trait?
4. If a circle is half shaded in, what does that mean?
1.