Name: ____________________
Per: ____ Date: _____
Genetics Test Practice Problems – Biology Honors
1.
If 8 legs is dominant over 4 legs and furry body is dominant over spiny body, then what would be the phenotypes of
the possible offspring between mom who is heterozygous for both traits and a dad who is homozygous recessive for
both traits?
P
2.
A widow belonging to blood group “A” had two children, of groups “O” and “B”, respectively. What must have been
the genotype and phenotype of the father? Also give the genotype of the widow and her children. Show your work.
P
3.
If pink color is dominant over orange color and long wings is dominant over stunted wings, what would be the
possible phenotypes of the offspring between a bug heterozygous for both traits and a bug heterozygous for color and
homozygous dominant for wings?
4.
Peter Griffin has blood type “B”. Lois Griffin has blood type “O”. They have two children of their own and one
adopted child. Meg has blood type “AB”, Chris has blood type “O”, and Stewie has blood type “B”. Which child is
adopted? Show your work.
5.
What is the probability that a family will have a boy, two girls, then a boy?
6.
Some cyntarians (imaginary creature) have ten tentacles while others have twelve. Cyntarians can be either blue or
red. List the possible offspring from a mating between a ten-tentacled, blue cyntarian and a heterozygous twelvetentacled, heterozygous red cyntarian. Show the fraction of genotypes and phenotypes of the offspring.
T = twelve tentacles
t = ten tentacles
R = red
r = blue
7.
A brown-eyed, curly-haired man and his brown-eyed, curly-haired wife plan to have children. They are each
heterozygous for each trait. List the fraction of possible genotypes and phenotypes of their offspring.
B = brown eyes b = blue eyes
C = curly hair
c = straight hair
8. Let’s do a test cross, a problem where you determine the parent’s genotypes from the offspring.
An offspring is homozygous dominant for eye-color. (B=brown eyes, b = blue eyes) What could the father be if the mother
is also homozygous dominant?
9.
Test cross #2: Two yellow-seeded pea plants are crossed. All of the 10 offspring are yellow except for two, which are
green. Which characteristic is dominant? _____________ What do you know about the parents? _______________
Can either one of them be homozygous? Explain______________________________________________________
__________________________________________________________________________________________________
10. Test cross #3: A blue-eyed individual and a brown-eyed individual are crossed and they have 5 blue-eyed and 6
brown-eyed offspring. What are the parent’s genotypes?
11. Sickle cell anemia is a disorder that causes anemia – pain in the joints, a swollen spleen, and frequent severe
infections. Heterozygous individuals are resistant to malaria. HbA = normal, HbS = sickle cell anemia What type of
trait is this? (Dom/Rec, Incomplete Dom, Codom?) ________________ Autosomal or sex-linked? _________
Joe isn’t homozygous for sickle cell anemia. What are his chances of having an allele for both sickle cell anemia and
normal blood if neither of his parents are homozygous for sickle cell anemia, but his mother’s mother, his mother’s sister
and his father’s father all had sickle cell anemia? ____ (pretend his grandfather some how miraculously survived)
Draw a pedigree and show the genotype of each individual. In other words, show your work.
12. Hemophilia is a disease in humans that causes the blood to clot slowly. What type of trait is this? ______________
______________ Label the genotypes for each of the numbered individuals and remember to show both the X and Y
chromosome. The carriers are not labeled, but you should shade them halfway after you complete the genotypes.
1
I.
= normal
2
= hemophiliac
3
II.
III.
6
9
9
8
7
5
4
10
11
IV.
13. Find the genotypes of each individual in the following pedigree for the inheritance of colorblindness. What type of
trait is this? ____________________________________________ The carriers are not labeled, but you should shade
them in after you complete the genotypes.
2
1
4
3
5
6
7
8
9
10
11
12
22
22
2
14. Find the genotypes of each individual in the following pedigree. Let shaded areas be scaly individuals. The
heterozygous creatures are not labeled, but you should shade them in after you complete the genotypes.
A = slimy , a = scaly
1
2
6
3
5
4
7
8
9
15. Achondroplasia is a type of autosomal dominant genetic disorder that is a common cause of dwarfism. If a zygote
inherits two copies of the dominant allele, this combination is lethal and the baby will be miscarried. Use the
information below to draw a pedigree to determine the chances for a baby to be born of normal stature to a couple
(Nancy and Jerry) that are both little people. Shade those with achondroplasia after drawing the family’s pedigree
then record the genotypes of all the individuals. Use A for the dominant allele.
Nancy’s family:
Nancy, her dad, and her sister do have achondroplasia.
Her mom doesn’t.
Jerry’s family:
Jerry and his mom do have achondroplasia.
His dad doesn’t.
16. Insulin is a hormone made by our pancreas. Insulin is made in response to a rise in the level of blood glucose after a
meal. The condition of diabetes mellitus results from an insulin deficiency. Diabetes may be inherited and is caused
by a recessive gene.
Use the information below to make a pedigree to determine the chances for Sally and Jack to have a child with
diabetes. Draw a family pedigree and record the genotypes of all the individuals below.
Sally’s family:
Sally, her dad, and her mom’s mom do not have diabetes.
Her mom, and her mom’s dad do have diabetes.
Jack’s family:
Jack, his mom, and his mom’s dad do not have diabetes.
His dad, his mom’s sister, and his mom’s mom do have diabetes.
What’s the probability that their offspring will have diabetes? ___________
17. In a certain family neither husband or wife is bald, but their three sons developed pattern boldness, a sex-linked trait.
Give the genotypes of the parents. Where in the family did the gene for pattern baldness come from?________ Draw
a pedigree to show how you know this.
18. And the challenge… In snapdragons, red flower color (___) is incomplete dominant with white (___). The normal
(broad) leaves (LB) are _____________ with narrow (grass-like) leaves (LN). If a red-flowered, broad-leaved plant is
crossed with a white-flowered, narrow-leaved one, what will be the phenotypes and their expected ratio in the F2
generation? Do this on another piece of paper.