Transcript Probability Discussion - Faculty Homepages (homepage.smc.edu)

Probability and Pedigree
Practice Problems
Practice

1. We will review the questions on pp. 1-4-through-1-5

2. We will look at the examples of pedigrees in your lab
manual.

3. You can try the pedigree/probability problems 1-29
and 1-31 on your own. You will apply the principles
reviewed on pp. 1-4 to 1-5 and also have you practice
drawing some pedigrees.

Please refer to Dr. Colavito’s homepage for solutions.
Begin with page 1-4

1.
– A) Probability of rolling a “5”= 1/6
– B) Probability of rolling an even number: 1/6 + 1/6 + 1/6 =
1/2
Problem 1 continued

1c) 1/6 x 1/6 x1/6 = 1/216

1d) 6x(1/216)=1/36

1e) 1/216 x 6 = 1/36

1f) 1 (any number) x 5/6 x 4/6 = 20/36= 5/9
Problem 2

First identify the probabilities of selecting various
colors:
– Jar 1: P (y)= 1/5 P (G) = 4/5
– Jar 2 :P (O) = 2/5 P(G) 3/5
– Jar 3 :P (P) 1/10
P(G) 9/10
Problem 2

A. 1/5 x 2/5 x 1/10 = 2/250 = 1/125

B. 4/5 x 2/5 x 9/10 = 72/250

C. 1-(probability of no green skittles, see part A.)= 11/125=124/125
Problem 2

D. calculate all possible combinations for each container:

(4/5 x 3/5 x 1/10) + (4/5 x 2/5 x 9/10) +
1/5 x 3/5 x 9/10) = 111/250
Problem 2

E. (2/5 x 1/10 x 4/5) = 8/250= 4/125
Problem 3 Autosomal Dominant

A. ¾

B. 4!/3!1! (1/4)3 (3/4)1= 3/64

C. ¼ x ¾ x/ ¾ = 9/64

D. 1-(probability that all will have straight little fingers)=
1-(1/4) 3= 63/64
Problem 4: Autosomal Recessive

A. 2/3

B. 2/3

Keep in mind the parents of Jessica and Jerry must be
heterozygous for in order to have a sibling that has CF.
Problem 4

C. 2/3 x 2/3 x 1/4 = 1/9

Remember to refer to your Punnett square
and you will see that with heterozygous
parents there is ¼ chance of cc.
Problem 4

D. 3!/2!1! (1/9)2 (8/9)1 = 8/243

E. 8/9 x 1/9 x 8/9 = 64/729
Problem 5: X linked recessive

½ that Polly has the “d” allele

½ x ¼ =1/8

½ x 3/8 x 1/8 = 3/128

5!/2!3! (1/8)2 (7/8) 3 = 3430/32768 =0.105
Let’s move onto Pedigrees

Discuss the pedigrees with your group and
determine pattern of inheritance and know
why you selected your answers.
Pedigrees (page 1-26)
A. autosomal dominant
 B. X linked dominant
 C. X linked recessive
 D. autosomal recessive
 E. X-linked dominant
 F. Autosomal recessive
 G. Autosomal Dominant
 H. X-linked recessive

Practice

1. We have reviewed the questions on pp. 1-4-t-5

2. We have looked at the examples of pedigrees in your
lab manual.

3. You can try the pedigree/probability problems 1-32
and 1-33 on your own. You will apply the principles
reviewed on pp. 1-4 to 1-5 and also have you practice
drawing some pedigrees.

Please refer to Dr. Colavito’s homepage for solutions.