1. A form of a gene is called a(n) _________.(For example, the gene for flower color in pea plants has two forms, one for purple and one for white. These are possible ________ for this gene.)

A. GenotypesB. GenomesC. AllelesD. Proteomes

Genotypes

Genomes

Alleles

Proteomes

25% 25%25%25%

2. A recessive allele is

A. a form of a gene that is always expressed

B. a form of a gene that can be hidden

C. the allele that is less common in the population

D. both B and C

a form

of a gene th

at is ...

a form

of a gene th

at can ..

the allele th

at is le

ss co

...

both B and C

25% 25%25%25%

3. Describing the physical appearance/ expression of a trait defines the _______________ of the individual.

A. PhenotypeB. GenotypeC. PrototypeD. Gene pool

Phenotype

Genotype

Prototype

Gene pool

25% 25%25%25%

4. Identifying the two alleles possessed by an individual for a trait (such as Rr) defines their __________________ .

A. PhenotypeB. GenotypeC. PrototypeD. Gene Pool

Phenotype

Genotype

Prototype

Gene Pool

25% 25%25%25%

5. An organism with two different alleles for a trait such as (Gg) is called

A. HomozygousB. HeterozygousC. HaploidD. Diploid

Homozygous

Heterozygous

Haploid

Diploid

25% 25%25%25%

The prefix hetero= different.

A heterozygous genotype is one where the individual has two different alleles (forms of the gene) for a trait.

6. Which of the following is true regarding the genotype of an individual with a dominant phenotype for a trait?

A. It must be homozygousB. It must be heterozygousC. It could be homozygous or

heterozygous

It must

be homozygous

It must

be heterozygous

It could be homozyg

ous...

33% 33%33%

7. Which of the following is true regarding the genotype of an individual with the recessive phenotype for a trait.

A. It must be homozygousB. It must be heterozygousC. It could be homozygous or

heterozygous

It must

be homozygous

It must

be heterozygous

It could be homozyg

ous...

33% 33%33%

The black fur allele is dominant in rabbits.Rabbits will have dark fur whether they have one

black allele or two. (Homozygous dominant or heterozygous will look the same.)

Rabbits can only have white fur if both of their alleles are the recessive white fur allele.

(Must be homozygous recessive.)

8. Which of the following is the correct way to set up a Punnett square for a cross of two cats that are both heterozygous for bushy tails? The bushy tail allele is B and the nonbushy tail allele is b.

A. .B. . C. .

.B. .

C. .

33% 33%33%Bb Bb

Bb

Bb

B Bb

b

B bB

b

o Each side of the Punnett square represents the possible alleles that can be passed down from one parent.

o Since each gamete (egg or sperm) has only one allele for each gene, only one letter should be placed over each square.

o A heterozygous parent has one of each allele, so 50% of the gametes have one allele and 50% of the gametes have the other.

B b

B

bFa

ther

’s s

perm

Mother’s egg

9. If the purple flower allele (P) is dominant and the white flower allele is recessive (p), can two plants with purple flowers produce a seed for a plant with white flowers?

A. YesB. No

Yes No

50%50%

If both are heteozygous for the trait,they may each pass down the white

allele.

10. If the purple flower allele (P) is dominant and the white flower allele is recessive (p), can two plants with white flowers produce a seed for a plant with purple flowers?

A. YesB. No

Yes No

50%50%

Since the white flower is the recessive allele,plants with this recessive trait must have two

recessive alleles, and therefore do not have any purple flower alleles to pass down.

X =

11. The widow’s peak allele is dominant (W), the nonwidow’s peak allele is recessive (w). If one parent is heterozygous for the allele (Ww) and the other parent does not have a widow’s peak (ww). What is the probability that their first child has a widow’s peak? (Hint: Draw a Punnett square)

A. 100%B. 75%C. 50%D. 25%E. 0%

100%75%

50%25% 0%

20% 20% 20%20%20%

w w

W Ww Ww

w ww ww

2 out of 4 = 50%

12. The parent’s from the previous problem have two children with widow’s peaks. What is the probability that their third child will have a widow’s peak?

A. 100%B. 75%C. 50%D. 25%E. 0%

100%75%

50%25% 0%

20% 20% 20%20%20%

13. Hitchhiker’s thumb is a recessive trait (t).A nonhitchhiker’s thumb is dominant (T).If two parents are heterozygous for the trait, what is the probabilitythat they will have a child with a hitchhiker’s thumb?

A. 100%B. 75%C. 50%D. 25%E. 0% 100%

75%50%

25% 0%

20% 20% 20%20%20%

T t

T TT Tt

t Tt tt

1 out of 4 (25%) probability to inherit recessive alleles from both parents.

14. The leg-headed (legs instead of antennae) allele is recessive in fruit flies (a). If a homozygous dominant fruit fly for the normal phenotype (AA) is mated with a leg-headed fruit fly (aa), what is the probability that they will have leg-headed offspring?

A. 100%B. 75%C. 50%D. 25%E. 0% 100%

75%50

%25% 0%

20% 20% 20%20%20%

Normal fruit flyLeg-headed fruit fly (antennaepedia)

A A

a Aa Aa

a Aa Aa

All the offspring will inherit a dominant allele from the homozygous dominant fruit fly. Therefore they can not have an offspring with the recessive trait.

15. A true-breeding yellow flowered plant is crossed with a true-breeding white flowered plant. The F1 generation has all yellow flowers. What is the probably outcome for the F2 generation?

A. All yellowB. All whiteC. 50% yellow, 50% white (1:1)D. 75% yellow, 25% white (3

yellow: 1 white)E. 75% white, 25% yellow (3

white: 1 yellow)

All yello

w

All white

50% yello

w, 50% w

hite (1

:1)

75% yello

w, 25% w

hite (3

...

75% white

, 25% yello

w (...

20% 20% 20%20%20%

• The true-breeding plants must be homozygous. (YY x yy)• The F1 generation must be heterozygous (Yy). Yellow

must be dominant.• The F2 produced by the F1 cross (Yy x Yy) should have a 3

to 1 phenotype ratio of yellow to white.

Y y

Y YY Yy

y Yy yy

16. What is the genotype ratio from a cross of two plants that are heterozygous for round seeds (R= round, r = wrinkled).

A. 3:1B. 1:1C. 1:2:1D. 9:3:3:1

3:011:01

1:02:01

9:3:3:1

25% 25%25%25%

In a heterozygous cross, 3 genotypes can be produced: RR, Rr or rr.

The probabilities are:

1 out of 4 RR

2 out of 4 Rr (can inherit R from egg and r from pollen or r from egg and R from pollen)

1 out of 4 rr_________________

1:2:1 ratio

R r

R RR Rr

r Rr rr

Pollen

Egg

17. The allele for purple flowers is dominant (P) in peas. White is recessive (p). If you have a pea plant with purple flowers which you want to determine is heterozygous or homozygous, which of the following is true?

A. It must be homozygousB. It must be heterozygousC. You could perform a test cross, which

is usually crossing with a recessive plant

D. You could perform a test cross, which is usually crossing with a homozygous dominant plant

It must

be homozygous

It must

be heterozygous

You could perfo

rm a te

st...

You could perfo

rm a te

s...

25% 25%25%25%

• A test cross can be used to determine the genotype of a organism with a dominant phenotype.

• It involves crossing with a recessive. • Recessive offspring can only be produced if the organism is

heterozygous.• If the results are all offspring with the dominant

phenotype, the test may be inconclusive (unless there is a very large number of offspring)

1.C

2. B

3. A

4. B

5. B

6. C

7. A

8. B

9.A

10.B

11.C

12.C

13. D

14. E

15. D

16. C

17.C