Pedigree Worksheet Biology Worksheet Template Page 2
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1
2n
n
X
X
9. Females with hemophilia have an easy genotype to identify. They are all
. Both recessive alleles must be
N
X
present for a female to have hemophilia. If one dominant allele is present (
), the individual will be normal for
blood clotting.
n
n
X
X
a) How many females have the genotype
? ______
N
N
N
n
X
X
X
X
10. Females who do not show the trait for hemophilia may be homozygous dominant (
) or heterozygous (
).
A heterozygous female is called a carrier. Examination of offspring can often determine which genotype the parents
have. If any child (son or daughter) has hemophilia, then the female must be heterozygous. If her son has
n
n
X
Y
X
hemophilia, he has genotype
. He inherited the Y from the father, so the other allele in his genotype (
) had to
n
n
n
X
X
X
come from the mother. If a daughter has hemophilia (
), she inherited an
from each parent, thus making the
N
n
X
X
genotype for the normal mother
.
a) What would be the genotype for the female who marries into the family in generation III? ______
b) List all the carrier females in the pedigree (by generation and number). ________________________________
N
N
X
X
c) It is possible that one of females could be
. List this female. ______________
B. Determining the pattern of inheritance and assigning genotypes.
When working through a pedigree, the first thing you need to do is figure out which characteristic is dominant- the shaded
one or the open one. Then you need to choose a letter (let’s use A) and begin assigning genotypes. Remember that recessive
individuals are always homozygous, so assign their genotypes first. Then go back and look at all the dominant individuals.
For some, you will only be able to determine one allele of the genotype, so just write the one capital allele followed by an
underscore (A_).
Fur Color in Mice
Key:
= white female
= black female
= white male
= black male
1. Draw the pedigree and the key.
2. Number the generations and the individuals in the pedigree.
3. Which characteristic is dominant? ______________
4. Which characteristic is recessive? ______________
5. Determine the genotypes of all individuals and write them on the pedigree.
*You will have three (A_)s.
6. What are the two possible genotypes for individuals labeled A_? ______ or ______
7. List the individuals who’s genotypes are A_. _________________________
C. Create your own pedigree.
Use colored pencils to create a pedigree with the following information. Follow the guidelines for a pedigree when creating
this one. Ray and Elaine were married in 1970. They both had normal vision. They had two daughters and then a son. Both
daughters, Alicia and Candace, had normal vision and never had any children of their own. The son, Mike was color-blind.
The son married Beth who also had normal vision and they had two children of their own, first Greg and then Victoria.
Victoria was color-blind, but Greg was not. Color-blindness is a sex-linked recessive trait.
*Do not forget what shapes are male and female. Place the names and genotypes of the people under their shape.
Color your individuals the following:
Red- for color-blindness
Green- unknown genotype
White- for regular vision
Blue- for individuals with regular vision but are carriers
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