Heredity (Introduction) MCQs Quiz | Class 10

Understanding Heredity: An Introduction

Heredity is a fundamental concept in biology that explains why offspring resemble their parents, yet also exhibit variations. It is the process by which traits are passed from one generation to the next. This section will help you revise the basic principles and terminology associated with heredity.

Key Concepts of Heredity

• Heredity: The transmission of characteristics from parents to offspring. It is the reason why children often look like their parents or grandparents.
• Variation: The differences among individuals of the same species. While traits are inherited, variations arise due to factors like sexual reproduction and environmental influences.
• Traits: Detectable characteristics or features of an organism, such as eye color, height, or presence of freckles. Traits can be inherited or acquired.
• Genes: The basic physical and functional units of heredity. Genes are specific sequences of DNA that code for particular proteins, which in turn determine traits. They are located on chromosomes.
• Alleles: Different forms of the same gene. For example, a gene for pea plant height might have two alleles: one for ‘tall’ and one for ‘dwarf’.
• Genotype: The genetic makeup of an organism, referring to the set of alleles it possesses for a particular gene. For instance, TT, Tt, or tt for pea plant height.
• Phenotype: The observable physical or biochemical characteristics of an organism, which are a result of its genotype and environmental interactions. For example, ‘tall’ or ‘dwarf’ plant.
• Dominant Trait: A trait that is expressed in an individual even if only one copy of the dominant allele is present (e.g., Tt results in tall plant if T is dominant).
• Recessive Trait: A trait that is expressed only when two copies of the recessive allele are present (e.g., tt results in dwarf plant if t is recessive). It is masked by a dominant allele.
• Homozygous: Having two identical alleles for a particular gene (e.g., TT or tt).
• Heterozygous: Having two different alleles for a particular gene (e.g., Tt).

Inheritance of Traits: A Basic Understanding

Gregor Mendel, often called the ‘Father of Genetics’, conducted experiments with pea plants that laid the foundation for our understanding of inheritance. He demonstrated that traits are inherited as discrete units (which we now call genes) and not by blending. Each parent contributes one allele for each gene to their offspring. The combination of these alleles determines the offspring’s genotype and subsequently its phenotype.

Examples of Human Traits

Here’s a simple table illustrating some common dominant and recessive human traits:

Quick Revision Points

• Heredity is the passing of traits from parents to offspring.
• Genes, made of DNA, are the units of heredity located on chromosomes.
• Alleles are different versions of a gene.
• Genotype is genetic makeup; phenotype is observable trait.
• Dominant alleles express their trait even with one copy; recessive alleles need two copies.

Practice Questions

1. The process by which characteristics are transmitted from parents to offspring is called:
   (A) Evolution (B) Heredity (C) Mutation (D) Adaptation
2. Which of the following refers to the observable characteristics of an organism?
   (A) Genotype (B) Allele (C) Phenotype (D) Gene
3. If an organism has two different alleles for a single trait, it is described as:
   (A) Homozygous (B) Heterozygous (C) Purebred (D) Dominant
4. What are the alternative forms of a gene called?
   (A) Chromosomes (B) Loci (C) Alleles (D) Traits
5. Which component of DNA carries genetic information?
   (A) Ribosomes (B) Proteins (C) Nucleotides (D) Genes