Mendelian Genetics
Multiple Choice
Identify the choice that best completes the statement or answers the question.
____
____
____
1. Mendel concluded that traits are
a. not inherited by offspring.
b. inherited through the passing of factors from parents to offspring.
c. determined by dominant factors only.
d. determined by recessive factors only.
2. When Mendel crossed true-breeding tall plants with true-breeding short plants, all the offspring were tall
because
a. the allele for tall plants is recessive.
b. the allele for short plants is dominant.
c. the allele for tall plants is dominant.
d. they were true-breeding like their parents.
3. How many different allele combinations would be found in the gametes produced by a pea plant whose
genotype was RrYY?
a. 2
c. 8
b. 4
d. 16
Completion
Complete each statement.
4. A pea plant that has two different alleles for the same trait is said to be ____________________.
Short Answer
5. How many recessive alleles for a trait must an organism inherit in order to show that trait?
6. What is the phenotype ratio of the offspring in the Punnett square shown in Figure 11-3?
RrYy
RY
Ry
rY
ry
RY
RRYY
RRYy
RrYY
RrYy
Ry
RRYy
RRyy
RrYy
Rryy
RrYy
rY
RrYY
RrYy
rrYY
rrYy
ry
RrYy
Rryy
rrYy
rryy
Seed Shape
R = Round
r = Wrinkled
Seed Color
Y = Yellow
y = Green
Figure 11–3
Essay
7. Explain why short plants reappeared in Mendel’s F2 generation of pea plants.
8. You wish to determine whether a tall pea plant is homozygous or heterozygous for tallness. What cross
should you perform to arrive at your answer? Explain your choice of cross.
Other
USING SCIENCE SKILLS
Heterozygous male guinea pigs with black, rough hair (BbRr) are crossed with heterozygous female guinea
pigs with black, rough hair (BbRr). The incomplete Punnett square in Figure 11-4 shows the expected results
from the cross.
BbRr
BR
Br
bR
br
BR
BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
BbRr
bR
BbRR
BbRr
?
bbRr
br
BbRr
Bbrr
bbRr
bbrr
Hair Color
B = Black
b = White
Hair Texture
R = Roughr =
Smooth
Figure 11–4
9. Using Tables and Graphs Identify the genotype of the offspring that would be represented in the square
labeled X in Figure 11-4.
10. Using Tables and Graphs Identify the phenotype of the offspring represented in the square labeled X in
Figure 11-4.
11. Analyzing Data In Figure 11-4, what are the different phenotypes of the offspring?
12. Analyzing Data In Figure 11-4, what are the genotypes of the offspring that have black, rough hair?
13. Calculating What fraction of the offspring in Figure 11-4 is expected to have white, smooth hair?
Mendelian Genetics
Answer Section
MULTIPLE CHOICE
1. ANS: B
2. ANS: C
3. ANS: A
PTS: 1
PTS: 1
PTS: 1
REF: p. 265
REF: p. 265
REF: p. 270
COMPLETION
4. ANS: heterozygous
PTS: 1
REF: p. 268
SHORT ANSWER
5. ANS:
An organism must inherit two recessive alleles for a trait in order to show that trait.
PTS: 1
REF: p. 265
6. ANS:
The phenotype ratio is 9 round, yellow peas: 3 round, green peas : 3 wrinkled, yellow peas : 1 wrinkled, green
pea.
PTS: 1
REF: p. 271
ESSAY
7. ANS:
When the heterozygous tall F1 plants produced gametes, their dominant allele for tallness segregated from
their recessive allele for shortness. As a result, some of their gametes had the dominant allele, while others
had the recessive allele. When the F1 plants self-pollinated, some male gametes with the recessive allele fused
with female gametes with the recessive allele during fertilization. The offspring that resulted, which were part
of the F2 generation, had two alleles for shortness and were therefore short.
PTS: 1
REF: p. 271
8. ANS:
The tall pea plant should be crossed with a short pea plant. If the tall pea plant is homozygous, all of the
offspring will be tall. If the tall pea plant is heterozygous, it is likely that about half of the offspring will be
tall and half will be short.
PTS: 1
OTHER
9. ANS:
REF: p. 265
The genotype of the offspring is bbRR.
PTS: 1
REF: p. 271
10. ANS:
The phenotype of the offspring is white, rough hair.
PTS: 1
REF: p. 271
11. ANS:
The phenotypes of the offspring are black, rough hair; black, smooth hair; white, rough hair; and white,
smooth hair.
PTS: 1
REF: p. 271
12. ANS:
Offspring with black, rough hair have the genotypes BBRR, BBRr, BbRR, and BbRr.
PTS: 1
REF: p. 271
13. ANS:
One sixteenth of the offspring are expected to have white, smooth hair.
PTS: 1
REF: p. 271