Download MONOHYBRID CROSSES Long hair is dominant to short hair in

MONOHYBRID CROSSES
1. Long hair is dominant to short hair in Hamsters. Show the results of a cross between a
homozygous short haired male and a pure long haired female.
a. Cross the offspring from #1 among themselves and show the expected results.
2. The allele for purple flowers is dominant over the allele for white flowers.
a. What type of offspring would you expect if you crossed a pure line purple flower with
one that is white? Show both genotypic and phenotypic ratios.
b. Cross the offspring from the preceding problem. Show genotypic and phenotypic ratios.
3. If a homozygous normally pigmented parent mates with an albino, what would be the expected
genotypes and phenotypes of the offspring?
4. In humans brown eyes are dominant over blue eyes.
a. If a heterozygous brown eyed male mates with a blue eyed female, what would be the
expected genotypic and phenotypic ratios of their offspring?
b. A brown eyed woman and a brown eyed man have two blue eyed children. What are
the chances that their next child will have blue eyes
5. Incomplete Dominance - Suppose a red flower and a white flower were cross-pollinated. The
flowers from the resulting seeds were neither red nor white but pink. Explain.
a. Cross the offspring from the preceding incomplete dominance problem. Give the
phenotypic and genotypic ratios.
6. Co- Dominance In shorthorn cattle, coat color may be red RR, white R’R’, or roan RR’. Roan
is an intermediate phenotype expressed as a mixture of red and white hairs. The following
data were obtained from various crosses:
a. Red x White à All Red
b. White x White à All White
c. Red x White à All Roan
d. Roan x roan à ¼ Red, ½ Roan, ¼ White
Human AUTOSOMAL DOMINANT TRAITS
7. A woman heterozygous for polydactyly, a condition that produces six fingers and six toes, is
married to a man without this condition. What are the chances that their children will have six
fingers and toes?
8. A young man’s father has just been diagnosed as having Huntington’s disease which is a
dominant trait. What is the probability that the son has inherited this disease?
9. Black hair is dominant over blonde hair. A woman with black hair whose father had blonde
hair reproduces with a blond-haired man. What are the chances of the couple having a blonde
child?
AUTOSOMAL RECESSIVE TRAITS
10. One parent has lactose intolerance, the inability to digest lactose, the sugar found in milk. The
other parent is heterozygous for the trait. What are the chances that their child will have
lactose intolerance?
11. Cystic fibrosis is an autosomal recessive disorder. A child has cystic fibrosis (CF) but his
parents are normal. What is the genotype of all persons mentioned?
12. One parent has sickle cell disease but the other parent is perfectly normal. What are the
possible phenotypes of their children?
a. A child has sickle cell disease but her parents do not. What is the genotype of each
parent? Explain.
1
INCOMPLETE AUTOSOMAL DOMINANCE
13. What are the chances that a person pure for straight hair who is married to a person pure for
curly hair will have a child with wavy hair?
14. Manx cats are those that have short tails. If two manx cats are bred and have 3 long tailed
kittens, 5 short tailed kittens and 2 with no tails at all: Explain how the trait for tail length is
inherited in these cats. Prove it … Show the genotypes of all the cats mentioned in this
question as PART of the evidence used in proof of your assumption.
DIHYBRID CROSSES
15. Some dogs bark when trailing, others are silent. The barking trait is due to a dominant
allele. Erect ears are dominant to drooping ears. What kind of pups would be expected from a
heterozygous, erect eared barker mated to a droop-eared silent trailer?
16. In humans, the ability to roll one’s tongue is determined by a dominant autosomal allele and
non tongue rolling by a recessive allele. Free earlobes are determined by a dominant
autosomal allele on another chromosome and attached earlobes are determined by a
recessive allele. Suppose a non tongue rolling man with free earlobes (whose mother had
attached earlobes), marries a woman with attached earlobes who can roll her tongue (but
whose father could not). What phenotypes might be expected in their offspring?
MONOHYBRID SEX LINKED
17. A couple has three boys and the mother is pregnant again. What is the probability that the
next child will be a boy?
18. Colorblindness is a recessive x-linked disorder.
a. A woman is color blind and her spouse has normal vision. If they produce a son and a
daughter, which will most likely be color-blind?
b. A color blind woman marries a man with normal vision. What kind of children would be
expected from such a union?
c. A normal male marries a normal female whose father was normal. They produce a
color blind boy. From which of his four grandparents did this child derive his gene for
color blindness?
MULTIPLE ALLELES
Human blood type is determined by co-dominant alleles. There are three different alleles, known as
IA, IB, and i. The IA and IB alleles are co-dominant, and the i allele is recessive.
The possible human phenotypes for blood group are type A, type B, type AB, and type O. Type A and
B individuals can be either homozygous (IAIA or IBIB, respectively), or heterozygous (IAi or IBi)
19.The genotype of a woman with B type blood is BO. The genotype of her husband is AO. What
are the possible genotypes and phenotypes of their children?
20. Mrs. Doe and Mrs. Roe both had babies at the same hospital at the same time. Mrs. Doe took
home a girl and named her Nancy. Mrs. Roe took home a boy and named him
Richard. However, Mrs. Roe was sure that she had given birth to a girl and she and her
husband brought suit against the hospital. Blood tests showed that Mr. Roe was type O and
Mrs. Roe was type AB. Mr. And Mrs. Doe were both type B. Nancy was type A and Richard
was type O. Had an exchange occurred? Can we prove how the change occurred?
2
Challenge Problems for extra points
1. A couple preparing for marriage have their blood typed along with the other required blood
tests. Both are AB. They ask you what types of blood their children may have. What would
you tell them and how would you explain your conclusions?
2. A woman sues a man for the support of her child. She has type A blood, her child type O, and
the man type B. Could the man be the father? Explain your answer.
3. A wealthy, elderly couple die together in an accident. Soon a man shows up to claim their
fortune, contending that he is their only son who ran away from home when a boy. Other
relatives dispute this claim. Hospital records show that the deceased couple were blood typed
AB and O. The claimant to the fortune was type O. Do you think that the claimant was an
imposter? Explain.
4. A woman is Rh positive and both of her parents are Rh positive. She marries a man who is Rh
negative. Is there any possibility that they may have any Rh negative children? Ignore
mutation in your answer.
5. A young man who has hemophilia is about to be married to a young lady. The young lady
seems to be normal but her father had hemophilia. The young lady has blue eyes and the
young man has brown eyes and his mother had blue eyes. The young lady has A type blood
and her father had O type blood. The young man has type AB blood and his father had B type
blood and his mother had O type blood. Show the Punnett Square for this cross. Give the
Phenotypic and Genoypic ratios. What percentage of their children will be blue eyed
hemophiliacs? What percentage of their children will be brown eyed, non-hemophiliacs, with B
type blood? What percentage of the children will have hemophilila? Give the probability of
their children having each of the four major blood types? What percentage of the males will
have hemophilia? What percentage of the females will have hemophilia?
Genetics: X Linked Genes
****In fruit flies, eye color is a sex linked trait. Red is dominant to white ****
6. What are the sexes and eye colors of flies with the following genotypes:
XRXr_____________ XRY ____________ XrXr ___________
XRXR____________ XrY____________
7. What are the genotypes of these flies:
white eyed, male ____________ red eyed female (heterozygous) ________
white eyed, female ___________ red eyed, male ___________
8. Show a cross between a pure red eyed female and a white eyed male.
What are the genotypes of the parents: ___________& _______________
How many offspring are:
i. white eyed, male ____
ii. white eyed, female ____
iii. red eyed, male ____
iv. red eyed, female ____
3
9. Show the cross of a red eyed female (heterozygous) and a red eyed male. What are the
genotypes of the parents? ____ & ___________
How many offspring are:
i. white eyed, male____
ii. white eyed, female ___
iii. red eyed, male ____
iv. red eyed, female ____
In cats, the gene for calico (multicolored) cats is codominant. Females that receive a B and an R
gene have black and orange splotches on white coats. Males can only be black or orange, but never
calico.
Here’s what a calico female’s genotype would look like: XBXR
10. Show the cross of a female calico cat with a black male.
What percentage of the kittens will be black and male? ______
What percentage of the kittens will be calico and male? ______
What percentage of the kittens will be calico and female? _____
11. Show the cross of a female black cat, with a male orange cat.
What percentage of the kittens will be calico and female? _____
What color will all the male cats be? ____
12. Consider this pedigree for the trait albinism (lack of skin pigment) in three generations of a
family. The solid represents the trait. Is this trait caused by a dominant or recessive allele?
How can you tell? What are the genotypes for the parents in Generation I? What are the
probable genotypes of the mates of the albino offspring in Generation II? What is the genotype
of Individual #4 in Generation III? Can you tell the genotype of Individual #3? Why or why not?
I
1
4
2
3
II
III
13. What is the probability that a mating between two carriers of a genetic disorder will produce an
offspring with a recessively inherited disorder? What is the probability that a phenotypic normal
child will be a carrier?
4