Principles of Inheritance and Variation
Test 5

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following represents a dihybrid cross phenotypic ratio?

3:1
9:3:3:1
1:1
1:2:1
2

A dihybrid cross results in a 9:3:3:1 phenotypic ratio in the F2 generation.

Which scientist used the fruit fly Drosophila melanogaster for genetic experiments?

Gregor Mendel
Thomas Hunt Morgan
Walter Sutton
Francis Crick
2

Thomas Hunt Morgan used Drosophila melanogaster to study linkage and recombination in genetics.

Which of the following best describes multiple allelism?

A gene with two alleles
A gene with three or more alleles
Two genes affecting the same trait
Genes located on the same chromosome
2

Multiple allelism occurs when a gene has three or more alleles, such as in the ABO blood group system.

Which of the following inheritance patterns is observed in color blindness?

Autosomal dominant
Autosomal recessive
X-linked recessive
Y-linked
3

Color blindness follows an X-linked recessive inheritance pattern, primarily affecting males.

Which inheritance pattern is followed by Huntington’s disease?

Autosomal dominant
Autosomal recessive
X-linked dominant
X-linked recessive
1

Huntington’s disease follows an autosomal dominant pattern, meaning only one copy of the mutant gene is needed for expression.

Which of the following statements about linked genes is correct?

Linked genes are found on different chromosomes.
Crossing over can separate linked genes.
Linked genes always follow the Law of Independent Assortment.
All genes on the same chromosome are always linked.
2

Crossing over can break the linkage between genes and create new allele combinations.

Which of the following statements about Down’s syndrome is incorrect?

It is caused by trisomy of chromosome 21.
It results in developmental and cognitive impairments.
It occurs due to the presence of an extra Y chromosome.
It is a type of aneuploidy.
3

Down’s syndrome is caused by an extra copy of chromosome 21, not the Y chromosome.

Which trait did Mendel study in pea plants to explain the inheritance of a single gene?

Seed shape
Stem color
Leaf texture
Root length
1

Mendel studied traits like seed shape to explain monohybrid inheritance patterns.

What is the chromosomal composition of a female with Turner’s syndrome?

47, XXY
45, XO
46, XY
47, XYY
2

Turner’s syndrome is characterized by the absence of one X chromosome, leading to a 45, XO karyotype.

Which term describes an individual having two different alleles for a gene?

Homozygous
Heterozygous
Hemizygous
Polygenic
2

An individual with two different alleles for a gene (e.g., Tt) is called heterozygous.

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