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¾Pedigrees = a valuable tool for = a valuable tool for
anyone working in the field of y
g
genetics. • Used to show relationships in families and resemble a family
families, and resemble a family tree. • Circles represent females, and squares represent males.
• Generations are represented by roman numerals on the LEFT side of the pedigree.
• Death is represented by a slash
is represented by a slash through through
the symbol
• Lines that connect circles and Lines that connect circles and
squares horizontally represent that reproduction has occurred.
occurred
• The further to the left an The further to the left an
individual is the older they are. • Any vertical lines that drop down from the center of the above horizontal line show the offspring of the parents.
DAD
MOM
OLDEST son
OLDEST son
I
I.
II
II.
Youngest g
daughter
• We can then mark offspring that exhibit or DO NOT exhibit certain characteristics, such as exhibit certain characteristics such as
eye color.
• Ex: The following pedigree shows family h f ll i
di
h
f il
members with blue eye color.
I.
II.
• Brown eyes (B) are dominant over blue blue eyes. We can deduct the I.
genotypes of some family members. Try to
family members. Try to predict what the genotypes of the above
genotypes of the above family are for eye color. II.
A. What is the genotype of the I.
mother? bb
B What is the genotype of the
B. What is the genotype of the son? bb
II
II.
C C
C. Can you deduce from the d d
f
th
above information what the genotype of the father is? Yes….Bb • How do you know? How do you know?
He must be heterozygous b/c he has a son with blue eyes (recessive trait)
son with blue eyes (recessive trait). • Now let’s discuss the story of sickle‐cell anemia. In Africa, there is a high incidence of i I Af i
h
i hi h i id
f
malaria. Malaria is caused by a parasite that is transmitted by mosquitoes. The parasite feeds on the hemoglobin protein in red blood cells. g
p
If there is mutated strain of hemoglobin in the red blood cells the parasite starves to death
red blood cells, the parasite starves to death and dies. The picture on the left shows a sickle red blood cell and the picture on the right
red blood cell and the picture on the right show a normal red blood cell.
• Persons who are homozygous for normal red blood cells easily die from malaria. Persons who are homozygous for mutated red blood cells usually do not die from malaria, but p
g
could die from complications resulting from their odd shaped red blood cells (sickle‐cell anemia) Individuals heterozygous also
anemia). Individuals heterozygous also usually do not die from malaria and are spared from the awful complications of
spared from the awful complications of sickle‐cell anemia.
• Using the following information, design a pedigree chart and designate which of the
pedigree chart and designate which of the family members is homozygous for normal g
( ),
yg
( ),
hemoglobin (HH), heterozygous (Hh), and homozygous recessive (hh). ~Mom‐survived malaria
~Dad‐ died from complications from sickle‐cell g
anemia at age 42.
~Son #1‐ survived malaria
~Son#2‐
Son#2 Survived malaria, has sickle
Survived malaria has sickle‐cell
cell anemia
anemia
~Daughter #1‐ survived malaria
Make a Key:
I.
Hh
hh
hh = Sickle; survives malaria & dies of sickle cell
& dies of sickle cell
Normal; survives
Hh = Normal; survives malaria
Normal; dies of malaria
HH = Normal; dies of malaria
HH = II.
Hh
hh
Hh
• If the daughter marries a man who has normal hemoglobin (HH) in his red blood cells what is the probability that
blood cells, what is the probability that their children will have sickle‐cell anemia? i ? 0 out of __.
f 4
H
H
H
HH
HH
h
Hh
Hh
• Would their family be wise to Would their family be wise to
take drugs that prevent a person from dying if infected with the malaria parasite? Why?
malaria parasite? Why?
Yes, b/c their children have Yes
b/c their children have
a 50% chance of being HH
a 50% chance of being HH and could die from malaria. • Nearsightedness is a recessive trait (n). Th h d d
The shaded regions show individuals who i
h i di id l h
are recessive for nearsightedness. N t G
Note: Generations need to be ti
dt b
labeled on the left hand side of pedigrees!
I.
N
Nn
II.
N?
III.
nn
N
Nn
nn
nn
Note: When you do not know if a dominant trait is homozygous dominant (NN) or heterozygous (Nn), then it is notated by N?
Nn
nn
Nn
Nn
Now you construct a pedigree!
• Left‐handedness (h) is a recessive trait.
• Bill and Mary have a son, Mike, and Bill and Mary have a son Mike and
daughter, Sue (youngest) that are right‐
handed They also have a middle
handed. They also have a middle daughter, Marie that is a lefty. Sue gets married to John (righty) and has three
married to John (righty) and has three children. Their oldest daughter, Sarah and their middle son Joe are right
and their middle son, Joe are right handed. Yet, their youngest son, Ryan is a lefty
a lefty.
Now you construct a pedigree!
Now you construct a pedigree!
1 Label
1.
Label the generations and label each the generations and label each
individual in the pedigree by placing their name below the shape
name below the shape.
2. Determine the genotypes of as many individuals as possible
individuals as possible.
Hh
I.
Hh
Mary
H?
II. Mike
III.
Bill
hh
Hh
Hh
Marie
Sue
J h
John
H?
H?
hh
Sarah
Joe
Ryan