Principles of Inheritance and Variation
Test 2

Correct answer Carries: 4.

Wrong Answer Carries: -1.

Which of the following statements best describes co-dominance?

Both alleles blend to form an intermediate phenotype
Only the dominant allele is expressed
Both alleles are expressed equally in the phenotype
Neither allele is expressed
3

In co-dominance, both alleles contribute equally to the phenotype, as seen in AB blood group.

Which of the following represents the genotype of a carrier female for hemophilia?

XX
XhX
XhY
XY
2

A carrier female for hemophilia has the genotype XhX, where one X chromosome carries the recessive hemophilia allele.

Which of the following statements regarding mutations is incorrect?

Point mutations involve a single nucleotide change.
Frameshift mutations occur due to insertions or deletions.
All mutations are harmful to an organism.
Mutations can be spontaneous or induced.
3

Not all mutations are harmful; some may be beneficial or have no effect.

Which of the following statements about Mendelian genetics is correct?

Mendel’s laws apply only to plants.
A recessive trait is always expressed in heterozygous individuals.
The Law of Independent Assortment applies to genes on different chromosomes.
Linked genes always assort independently.
3

The Law of Independent Assortment applies to genes on different chromosomes but may not hold true for linked genes.

Which of the following statements about sex determination is incorrect?

Humans follow the XY system of sex determination.
Birds use the ZW system for sex determination.
Insects such as grasshoppers follow the XO system.
All mammals follow the ZW system of sex determination.
4

Mammals follow the XY system, where males have XY chromosomes and females have XX.

Which of the following genetic disorders is caused due to a point mutation in the β-globin gene?

Down’s syndrome
Sickle-cell anemia
Turner’s syndrome
Hemophilia
2

Sickle-cell anemia is caused by a single base substitution in the β-globin gene, leading to the formation of abnormal hemoglobin.

What is the genetic composition of a male in the XY sex determination system?

XX
XY
XO
ZZ
2

In the XY sex determination system, males have XY chromosomes, while females have XX.

Which of the following inheritance patterns is exhibited by human blood groups?

Incomplete dominance
Co-dominance and multiple allelism
Polygenic inheritance
Pleiotropy
2

Human blood groups show co-dominance (A and B alleles) and multiple allelism (IA, IB, and i alleles).

What is the term for a single gene controlling multiple phenotypic traits?

Polygenic inheritance
Pleiotropy
Co-dominance
Multiple allelism
2

Pleiotropy occurs when a single gene affects multiple phenotypic traits, such as in sickle-cell anemia.

Which of the following is an example of a disorder caused by non-disjunction of sex chromosomes?

Down’s syndrome
Klinefelter’s syndrome
Thalassemia
Sickle-cell anemia
2

Klinefelter’s syndrome (47, XXY) results from the non-disjunction of sex chromosomes during meiosis.

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