Problem 19 - A Complete Resource Book in Chemistry for JEE Main

Question

An alteration in the base sequence of nucleic acid molecule is (a) dislocation (b) replication (c) duplication (d) mutation

Step-by-Step Solution

Answer

An alteration in the base sequence of nucleic acid is a mutation.

Step 1: Understanding DNA Structure

DNA is composed of a sequence of nucleotides, which are the building blocks. Each nucleotide consists of a sugar, a phosphate group, and a nitrogenous base. The order in which these bases are arranged forms the genetic information.

Step 2: Defining Key Terms

- **Dislocation** refers to a displacement and is not a typical term used in genetic alterations. - **Replication** is the process by which DNA makes a copy of itself during cell division. - **Duplication** is the production of one or more copies of any piece of DNA, which includes a gene or entire chromosome. - **Mutation** is a change in the DNA sequence that affects genetic information.

Step 3: Identifying Alteration

The problem asks about an alteration in the genetic base sequence. Such a change is known as a 'mutation,' which can result in variations of protein products and sometimes lead to genetic disorders.

Step 4: Confirming the Correct Answer

Based on the definitions, a change to the base sequence, like changing or altering nucleotides, is classified as a 'mutation.' Therefore, the correct answer is (d) mutation.

Key Concepts

DNA Structure

DNA, or deoxyribonucleic acid, is the blueprint for life. It is composed of molecules called nucleotides, which serve as the fundamental building blocks. Each nucleotide consists of three essential components: a sugar molecule (deoxyribose), a phosphate group, and a nitrogenous base. The nitrogenous bases come in four types: adenine (A), thymine (T), cytosine (C), and guanine (G). These bases pair specifically – adenine always with thymine, and cytosine with guanine – forming the famous double helix structure.
The sequence of these bases along the DNA strand forms the genetic code, which instructs cells how to build proteins. The double helix is incredibly stable, allowing each strand to serve as a template during cell replication. Without this precise structure, the transfer of genetic information would be impossible.

Nucleotide Sequence

The nucleotide sequence is the particular order of nucleotides in a DNA molecule. This sequence dictates the composition and function of every living organism by determining which proteins are produced, and in what order.
Each sequence of three bases, known as a codon, corresponds to a specific amino acid, the building block of proteins. When a sequence instructions are followed, proteins are created that perform vital functions in the body. For example:

• A sequence coding for hemoglobin assists in transporting oxygen in the blood.
• A sequence that instructs the creation of enzymes can aid in digesting food.

Any change to a nucleotide sequence can have significant ramifications. This is because even a single base alteration can change an entire protein, impacting its functionality.

Genetic Alteration

Genetic alteration refers to changes in the nucleotide sequence of DNA. One common form of genetic alteration is a mutation, which can occur due to errors during DNA replication or from environmental factors like radiation. Mutations can lead to:

• New traits in organisms, which may be beneficial, neutral, or harmful.
• Genetic diversity, offering evolutionary advantages.
• Genetic disorders, resulting from harmful mutations that disrupt normal protein functions.

Some types of mutations include substitutions (where one base is replaced by another), insertions (where extra bases are added), and deletions (where sections of DNA are lost). While occasionally harmful, genetic alterations are a critical part of evolution and biological innovation, allowing organisms to adapt to their environments over time.