- In humans, brown eyes (B) are dominant over blue (b)*. A brown eyed man and a blue eyed woman have three children, two of whom are brown eyed and one of whom is blue eyed. Draw the punnett square that illustrates this. (*Actually, the situation is complicated by the fact that there is more than one gene involved in eye color, but for this example, we'll consider only this one gene).
- What are the genotypes of the children?
- If blue is recessive, what must the woman's genotype be?
- If that's her genotype, what kinds of gametes can she produce?
- If the man has brown eyes, but has a blue eyed child what must his genotype be?
- If that's his genotype, what kinds of gametes can he produce?
- In dogs, there is an hereditary deafness caused by a recessive gene, “d.” A kennel owner has a male dog that she wants to use for breeding purposes if possible. The dog can hear, so the owner knows his genotype is _________? If the dog’s genotype is Dd, the owner does not wish to use him for breeding so that the deafness gene will not be passed on. This can be tested most efficiently by breeding the dog with what genotype? Draw the Punnett squares to illustrate these two possible crosses.
- What percentage of the offspring would be expected to be hearing?
- What percentage of the offspring would be expected to be deaf?
- How could you tell the genotype of this male dog?
- Using Punnett square(s), show how two hearing dogs could produce deaf offspring.
- A man and a woman living in a tropical area where malaria is prevalent have 7 children. The genotypes of these children are ss, Ss, SS, ss, Ss, Ss, and SS. (SS makes all normal hemoglobin, ss makes all abnormal hemoglobin, Ss makes an intermediate type of hemoglobin)
- What is the genotype of the parents?
- How many of their children would you expect to live to adulthood and reproduce?
- What is the survivors genotype?
- Ms. Johnston,
Ms. Johnson, and Ms. Johnstone all entered the same hospital and gave birth to
baby girls on the same day, and all three babies were taken to the nursery to
receive care, there. Someone later claimed that the hospital mixed up the
babies. As a hospital administrator, it is your job to make sure that each pair
of parents has the correct baby, so you order blood typing to be done on all
the parents and all the babies. Here are the results:
Ms. Johnston
– A
Mr. Johnston
– B
Ms. Johnson –
B
Mr. Johnson –
O
Ms. Johnstone
– A
Mr. Johnstone
– A
Baby 1 – O
Baby 2 – AB
Baby 3 – B
Which baby
belongs to which parent?
Who else
could have been the parents of baby 1?
Who
else could have been the parents of baby 3?-
When the gene that codes for a trait is on the X chromosome it is called __________? A man that is not affected with hemophilia has a son with a woman that is not affected with hemophilia, and their son has hemophilia.
- What is the genotype of the mother?
- What do we call this?
- What percentage of their offspring will have the recessive gene for hemophilia but not be affected with the disease?
- What are the changes that their next son will also have hemophilia?
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