Principles of Inheritance and Variation Chapter-Wise Test 12

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following genetic disorders is incorrectly matched with its cause?

Down’s syndrome - Trisomy 21
Turner’s syndrome - 45, XO
Klinefelter’s syndrome - 47, XYY
Edward’s syndrome - Trisomy 18
3

Klinefelter’s syndrome is caused by the XXY karyotype, not XYY.

Which of the following statements about mutation is incorrect?

Mutations can be beneficial, neutral, or harmful.
All mutations are inherited by the next generation.
Point mutations involve a single nucleotide change.
Frameshift mutations occur due to insertions or deletions.
2

Not all mutations are inherited; only those in germ cells can be passed to the next generation.

Which of the following correctly describes pleiotropy?

One gene affects multiple traits
Multiple genes affect one trait
Two alleles blend to form an intermediate phenotype
Genes located on the same chromosome are inherited together
1

Pleiotropy occurs when a single gene influences multiple phenotypic traits, such as in phenylketonuria.

Which of the following statements about sex-linked inheritance is incorrect?

Color blindness is an example of X-linked inheritance.
Y-linked traits are inherited only by male offspring.
X-linked recessive disorders are more common in males than females.
Females cannot inherit X-linked recessive disorders.
4

Females can inherit X-linked recessive disorders if they receive two copies of the affected allele (one from each parent).

What is the genetic cause of sickle-cell anemia?

Trisomy of chromosome 21
Substitution of glutamic acid by valine in hemoglobin
Deletion of X chromosome
Duplication of the HBB gene
2

Sickle-cell anemia is caused by a single base substitution in the β-globin gene, leading to the replacement of glutamic acid with valine.

Which of the following is an incorrect statement about multiple allelism?

A gene can have more than two alleles in a population.
An individual can inherit more than two alleles for a single gene.
ABO blood group is an example of multiple allelism.
Multiple allelism contributes to genetic diversity.
2

Each individual inherits only two alleles for a gene, even if multiple alleles exist in the population.

Which of the following represents an example of pleiotropy?

ABO blood group
Sickle-cell anemia affecting multiple organs
Incomplete dominance in flower color
Polygenic inheritance of skin color
2

Pleiotropy occurs when a single gene affects multiple traits, as seen in sickle-cell anemia, which impacts oxygen transport and organ function.

Which of the following statements correctly defines a dominant allele?

An allele that is expressed only in the homozygous state
An allele that is always recessive
An allele that is expressed even in the heterozygous state
An allele that does not contribute to the phenotype
3

A dominant allele is expressed in both homozygous (AA) and heterozygous (Aa) conditions.

Which of the following best describes the principle of segregation?

Genes on the same chromosome assort together
Two alleles of a gene separate during gamete formation
Dominant alleles always mask recessive alleles
Genes interact to control a single trait
2

The principle of segregation states that two alleles for a trait separate during gamete formation and recombine during fertilization.

Which genetic phenomenon explains why genes located close together on the same chromosome tend to be inherited together?

Independent assortment
Linkage
Mutation
Crossing over
2

Linkage occurs when genes close to each other on the same chromosome are inherited together.

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