Introduction to Cell & Molecular Biology
(BIOL121) - Dr. S.G. Saupe (ssaupe@csbsju.edu); Biology Department, College of St. Benedict/St. John's
University, Collegeville, MN 56321 |

Answers to the Three Dozen Genetics Problems

*(if you think I have
coded in a mistake to the questions, please
let me know)*

1a.
M

1b.
Z, z

1c.
AB, aB

1d.
RT, Rt, rT, rt (assuming no linkage)

1e.
AbCDEf, AbcDEf

2a.
1

2b.
1

2c.
2

2d.
2

2e.
6

3a.
dom

3b.
dom

3c.
dom, dom

3d.
dom, dom

3e.
A, C, D, E are dom; B and F are rec

4a.
3 yellow : 1 green or 75% yellow
25% green

4b.
100% yellow

4c.
100% yellow

5a.
Ww

5b.
Ww (black) or ww (white)

5c.
1 black : 1 white or 50% black
50% white

6a.
25% chance or 1/4 probability

6b.
50% chance or 1/2 probability

6c.
assuming that the female is homozygous dom, there is 0% chance of an
albino offspring - but, you can't be sure the female is homozygous dom, even if
the trait hasn't shown up for three generations.

7.
Aa x Aa (both heterozygous)
25% probability that the next child will be
albino.

8.
Ff (heterozygous)

9.
Yy x yy (the yellow parent is
heterozygous, the green is homozygous recessive)

10.
Note: widow's peak is dominant.
50% prbability that any one child will
have a widow's peak. There is a 1/2
x 1/2 = 1/4 or 25% chance that BOTH
will have widow's peak.

11.
50% brown or blue

12.
You can't be certain that he is homozygous dominant, but the probability is good
that he is. You could do a
statistical test, like chi square
to "prove" our conclusion.

13.
F (we could both be heterozygous,
therefore, there is 25% chance that
one received both recessive alleles)

14.
F since the trait is dominant, I
must be Rr or RR.

15.
F

16.
F (if Linda is homo dom then there is 100% probability Erin can taste it)

17.
T (since Im homo rec, she must receive the allele from me)

18.
T (although genetic surprises do happen)

19.
T

20.
F (they could have O if Linda is heterozygous)

21.
F

22.
F (at least one parent must have a dominant allele - could be homozygous dom or
heterozygous. The other parent must have a recessive allele - could be
heterozygous or homo rec) 23. T (they receive it from Linda)

24.
F (he could be if Evelyn is heterozyg)

25.
F (if Evelyn is heterozy then it is true, but if Evelyn is homo dom then there
is no chance)

26.
T

27.
F (they could both be heterozygous, then yield 1/4 or 25% with FH)

28.
T

29.
F (each parent could be heterozygous)

30.
F

31.
T (at least three)

32.
F (since it is a 3:1 ratio both parents must be heterozygous)

33.
F (50% would be expected. The man
must be homoz rec and the woman
heteroz since her rather was homo rec)

34.
T

35.
T

36.
F (one parent must have freckles)

37.
F (4/52). The odds of picking an
Ace of Spades is 1/52.

38.
T

39.
F (1/4 or 25%. The probability of
two independent events occurring is the product of the individual probabilities.
Thus 1/2 times 1/2 equals 1/4.
As an example, the probability of any one child being a female is 1/2.
Even if a family has 10 children,
all boys, the probability of the next child
being a girl is 1/2. However, the
probability of ALL 10 children being
boys is 1/2 times 1/2 times 1/2.....(ten times).

Last updated: July 14, 2009 � Copyright by SG Saupe