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Practice probability questions:

1. What is the probability of:
a. tossing a fair coin and getting 5 heads in a row?
b. tossing a fair coin and getting two heads & a tails [in any order]?
c. tossing two identical fair coins and getting heads on both the first time & tails on both the second?
d. tossing two identical fair coins and getting heads on one & tails on the other both times?
e. tossing two non- identical fair coins and getting heads on the dime, tails on the penny the first time & tails on the dime, heads on the penny the second time?

2. It is now possible to test people for heterozygosity of the cystic fibrosis (cf) gene. Two known heterozygotes are married, and plan to have six children. What is the probability that they will have:
a. four girls?
b. exactly one child with cf?
c. that the third and fifth children have cf, but the others are normal?
d. three with cf?
e. five with cf?
f. only one boy?
g. only one boy, and three children with cf?
h. only one boy, and three children with cf?
i. only one boy, and he is the only child with cf?

3. Two people of normal phenotype have had a child with Niemann-Pick disease, a lethal recessive trait.
a) What is the probability that their next child will be afflicted?
b) If they have three more children, what is the probability that they will have one more child with Niemann-Pick disease?
c) Two more?
d) All three?
e) That the first two will be normal but the third will be afflicted?

4. Calculate the probability of a monohybrid cross resulting in a family of five, with (one of these at a time):
a) 2 males and 3 females
b) 3 males and 5 females
c) 3 dominant phenotypes and 2 recessive phenotypes
d) 2 dominant phenotypes and 3 recessive phenotypes

Now, make up your own problems.  Share with classmates.
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