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JAMB Biology Mock Test

Total questions: 20

Worksheet time: 10mins

Name
Class
Date
1.

In a dihybrid cross involving two heterozygous parents (AaBb × AaBb), what is the expected phenotypic ratio?

a)

3:1

b)

9:3:3:1

c)

1:2:1

d)

1:1:1:1

2.

Which of the following best explains dihybrid inheritance?

a)

Inheritance of one gene pair

b)

Inheritance of two independent gene pairs

c)

Inheritance of linked genes

d)

Inheritance of multiple alleles

3.

The genotypic ratio of a dihybrid cross between two heterozygous parents (AaBb × AaBb) is:

a)

9:3:3:1

b)

1:2:1:2:4:2:1:2:1

c)

3:1

d)

1:1:1:1

4.

In dihybrid inheritance, how many different types of gametes can be produced by an organism with genotype AaBb?

a)

2

b)

4

c)

8

d)

16

5.

A cross between two pea plants with genotypes RrYy × RrYy results in which phenotypic ratio?

a)

9 round yellow : 4 wrinkled yellow : 2 round green : 1 wrinkled green

b)

9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green

c)

9 round yellow : 3 wrinkled yellow : 3 round green : 1 wrinkled green

d)

9 round yellow : 3 round green : 2 wrinkled yellow : 2 wrinkled green

6.

If a dihybrid cross produces offspring with a 9:3:3:1 ratio, the parents must have been:

a)

Homozygous dominant

b)

Homozygous recessive

c)

Heterozygous for both traits

d)

Heterozygous for one trait only

7.

In a dihybrid cross, the probability of obtaining an offspring with both recessive traits is:

a)

1/16

b)

3/16

c)

9/16

d)

12/16

8.

How many phenotypes are possible in a dihybrid cross involving two heterozygous parents?

a)

2

b)

3

c)

4

d)

9

9.

Which of these combinations represents a dihybrid cross?

a)

Tt × Tt

b)

AaBb × AaBb

c)

AA × aa

d)

Bb × Bb

10.

What is the expected proportion of offspring with dominant phenotypes for both traits in a dihybrid cross (AaBb × AaBb)?

a)

1/16

b)

3/16

c)

9/16

d)

12/16

11.

If two heterozygous tall, yellow-seeded pea plants (TtYy × TtYy) are crossed, what fraction of the offspring will be short with green seeds?

a)

1/16

b)

3/16

c)

9/16

d)

12/16

12.

In a dihybrid cross, a 9:3:3:1 ratio suggests:

a)

Codominance

b)

Complete dominance and independent assortment

c)

Linked genes

d)

Incomplete dominance

13.

Which of the following genotypes represents a heterozygous dihybrid organism?

a)

AABB

b)

AaBB

c)

AaBb

d)

Aabb

14.

In dihybrid crosses, the 9:3:3:1 ratio is an example of:

a)

Genotypic ratio

b)

Phenotypic ratio

c)

Mendelian ratio

d)

Monohybrid ratio

15.

In pea plants, round seeds (R) are dominant to wrinkled seeds (r), and yellow seeds (Y) are dominant to green seeds (y). What is the genotype of a plant that is heterozygous for both traits?

a)

RrYy

b)

RrYY

c)

RRyy

d)

rrYy

16.

A dihybrid test cross involves crossing an organism with an unknown genotype with:

a)

A homozygous dominant organism

b)

A homozygous recessive organism

c)

A heterozygous organism

d)

A hybrid organism

17.

In a dihybrid cross between AaBb and aabb, the proportion of offspring with the genotype AaBb will be:

a)

1/4

b)

1/8

c)

1/2

d)

3/4

18.

How many types of genotypes are expected from a dihybrid cross between two heterozygous parents?

a)

4

b)

9

c)

16

d)

8

19.

In a dihybrid cross, which of the following represents a possible combination of gametes from a parent with genotype AaBb?

a)

AB, Ab, aB, ab

b)

AA, BB, aa, bb

c)

Aa, Bb, AB, ab

d)

AaBb, Aabb, aaBB, AABB

20.

When two heterozygous dihybrids are crossed, the least frequent phenotype is likely to be:

a)

Both dominant traits

b)

Both recessive traits

c)

One dominant, one recessive trait

d)

All traits in the heterozygous form