Gene Structure and Its Role in Heredity with NCERT Examples
A gene is a specific sequence of nucleotides in DNA or RNA, typically located on a chromosome, that serves as the fundamental unit of inheritance. Genes control the transmission and expression of one or more traits by determining the structure of particular polypeptides, especially proteins, or by influencing the function of other genetic material.
The concept of a gene is central to the study of biology and genetics, helping us understand how traits and characteristics are passed down from one generation to the next. By defining what a gene is and understanding how it operates within the cell, students and educators gain foundational insight into heredity, variation, and biological function.
Genes are not visible to the naked eye but are present in the DNA within the nucleus of every cell. The study of genes forms the basis for understanding more advanced topics such as genetics, biotechnology, and molecular biology.
Detailed Explanation of Genes: Structure and Function
Genes are made up of sequences of nucleotides. Each gene is situated at a specific location, known as a locus, on a chromosome. The nucleotide sequence within a gene encodes the information needed for the synthesis of proteins or the regulation of other genetic functions.
Chromosomes are long thread-like structures found in the nucleus of cells. They are composed of DNA and proteins, with many genes arranged linearly along their length. Genes provide the instructions for building and maintaining the organism. In this way, they serve as blueprints for everything from eye color to blood type.
While genes mainly function by coding for proteins, some genes also play regulatory roles, controlling when and how other genes are expressed.
Examples of Genes and Their Roles
A classic example is the gene that determines blood type in humans. Variations within this gene result in the A, B, AB, or O blood groups. Another example includes genes that control flower color in plants or coat color in animals.
Genes can also be linked to the development of inherited diseases. For instance, a particular gene mutation can result in sickle cell disease or cystic fibrosis, demonstrating the gene’s impact on health.
Many characteristics, such as height or skin color, are influenced by several genes working together, a concept known as polygenic inheritance.
Step-by-Step: How Do Genes Work?
- Genes are positioned on chromosomes within the cell’s nucleus.
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The nucleotide sequences in a gene provide instructions for making proteins.
This process occurs through the transcription of DNA to RNA and the translation of RNA to protein.
- These proteins perform essential roles in the structure, function, and regulation of the body's tissues and organs.
- Any change, or mutation, in the gene sequence can affect how these proteins are made and, therefore, an individual’s traits or health.
Key Definitions and Scientific Principles
| Term | Definition | Example |
|---|---|---|
| Gene | A sequence of nucleotides in DNA or RNA, located on a chromosome, that governs the inheritance and expression of traits. | Gene influencing eye color, or a gene coding for hemoglobin. |
| Chromosome | A long DNA molecule containing many genes and associated proteins. | Human chromosome 1 contains hundreds of genes. |
| Inheritance | The process by which genetic information is passed from parents to offspring. | Inherited blood group or hair type. |
Comparison Table: Gene, Chromosome, and DNA
| Aspect | Gene | Chromosome | DNA |
|---|---|---|---|
| Definition | Sequence of nucleotides coding for protein/RNA | Structure with many genes and DNA | The molecule carrying genetic code |
| Function | Controls traits | Organizes genetic material | Stores genetic information |
| Location | On chromosomes | In cell nucleus | Found in nucleus and mitochondria |
Scientific Significance
The discovery and understanding of genes have revolutionized biology. Genes explain inheritance patterns, mutations, and biological diversity. They also help scientists and medical professionals study diseases, facilitate agricultural advancements, and enable biotechnological innovation.
The term "gene" was first used in the early twentieth century to describe these hereditary units, which are now recognized as specific sequences within DNA or RNA.
Genes remain a foundational concept for exploring more complex biological processes such as Mendelian Genetics, and biotechnology.
Practice and Further Learning
- Read further about genetics basics: Basics of Genetics
- Explore how genes work in inheritance: Principles of Inheritance and Variation
- Need more information about chromosomes? Difference Between Gene and Chromosome
- Discover DNA structure: DNA Structure
Summary and Next Steps
Genes are the basic unit of inheritance, encoded in DNA or RNA, and responsible for the traits and biological functions of all living organisms. By learning how genes work, students build a strong foundation for exploring more advanced topics in biology, medicine, and biotechnology.
Continue your learning through Vedantu’s detailed concept pages and explore related topics such as Gene Definition, Molecular Basis of Inheritance, and Gene Regulation.
FAQs on What is a Gene? Definition, Structure, Function & Examples
1. What is a gene in simple words?
A gene is a segment of DNA that contains instructions for making a specific protein or RNA, which determines certain traits or functions in living organisms. Genes are called the basic units of heredity because they are passed from parents to offspring and control characteristics like eye color, blood type, or flower color in plants.
2. What is the function of a gene?
The main function of a gene is to provide the code for building proteins or functional RNA molecules. Genes control traits and bodily functions by:- Directing the synthesis of proteins (protein-coding genes)- Regulating when and how much a protein or RNA is produced- Influencing characteristics such as growth, metabolism, and appearance
3. Where are genes located in the cell?
Genes are located on chromosomes inside the cell nucleus.- Each chromosome is made of a long DNA molecule containing many genes.- Humans have 23 pairs of chromosomes, and each gene has a specific spot called a locus on a chromosome.
4. What is the difference between gene and chromosome?
A gene is a smaller unit of DNA that codes for a specific trait, while a chromosome is a long DNA molecule containing many genes.- Genes are specific segments on DNA.- Chromosomes organize, package, and carry genes during cell division.- Each human cell has about 20,000–25,000 genes distributed on 46 chromosomes.
5. What are alleles in genetics?
Alleles are alternative forms of the same gene that exist at the same locus on homologous chromosomes.- Alleles produce variations in inherited traits, like tall (T) or dwarf (t) plants.- The combination of alleles determines an organism’s genotype and phenotype.
6. What are some examples of genes?
Examples of genes include:- Insulin gene (INS): Controls production of insulin for blood sugar regulation.- Hemoglobin gene (HBB): Makes the hemoglobin protein in red blood cells.- Pea plant color gene: Determines purple or white flowers (as studied by Mendel).
7. What is DNA and gene difference?
DNA is the molecule that stores genetic information; a gene is a specific section of DNA that carries instructions for a genetic trait.- DNA forms the chemical basis of heredity.- Genes are functional units within DNA, each coding for a unique protein or function.
8. What is gene mutation?
Gene mutation is a permanent change in the DNA sequence of a gene.- Mutations can alter protein structure or function, sometimes causing genetic diseases or variation.- Examples include sickle cell anemia and cystic fibrosis mutations.
9. How do genes affect inheritance?
Genes are inherited from parents and determine the traits seen in offspring.- Each parent provides one allele for each gene.- The combination of alleles determines the genotype and phenotype of the child.- Mendelian inheritance explains how genes are passed and segregated during reproduction.
10. What is the relationship between gene, allele, and locus?
A gene is the basic unit of heredity, an allele is a variant form of a gene, and locus is the physical position of a gene on a chromosome.- Each gene may have multiple alleles.- Example: The gene for blood group (ABO) has alleles IA, IB, and i, and is found at a fixed locus.
11. How does a gene control a trait?
A gene controls a trait by coding for a protein or RNA that performs a specific biological function.- The protein produced by the gene influences the development of a visible characteristic or physiological function, such as eye color or enzyme activity.
12. What is meant by gene expression?
Gene expression is the process by which the information in a gene is used to synthesize a functional product (protein or RNA).- Gene expression involves two main steps: transcription (making RNA) and translation (producing protein).- Not all genes are active (expressed) in all cells or at all times.
