What are genes?
Genes are segments of DNA that carry the instructions to make specific proteins. These proteins determine an organism’s characteristics, such as eye colour, blood type, or how tall a plant grows.
Genes are located on chromosomes, which are long strands of DNA found in the nucleus of most cells.
Each gene contains a specific sequence of DNA bases (A, T, C, G), and this sequence forms a code for building proteins. Just like how letters form words, base sequences form genetic instructions.
Relationship Between DNA, Genes, Chromosomes, and Proteins
- DNA is the molecule that stores genetic information.
- A chromosome is a long strand of DNA wound around proteins.
- A gene is a specific section of DNA on a chromosome that codes for a protein.
- A protein is made when the gene’s code is used in a process called protein synthesis.
This relationship is often summarized as:
Gene → Code → Protein → Trait
Protein Synthesis (Simplified View)
Proteins are made in two main steps:
- Transcription – The gene’s code is copied from DNA to a molecule called mRNA (messenger RNA) in the nucleus.
- Translation – The mRNA travels to a ribosome, where the code is used to assemble amino acids into a specific protein.
Each gene carries the code for one specific protein, and different proteins carry out different functions in the body (like enzymes, hormones, or structural materials).
Alleles and Variation
- A gene can have different forms, called alleles.
- For example, a gene for flower colour may have one allele for red and another for white.
- These variations in alleles lead to genetic diversity among individuals.
In humans and most animals, each individual has two copies of each gene — one from each parent. The combination of alleles you inherit determines your traits.
Mutations
A mutation is a change in the base sequence of a gene. This may result in:
- No change (silent mutation)
- A different protein being made
- A protein that doesn’t work properly
- Sometimes, genetic diseases like sickle cell anaemia
Mutations can occur naturally or due to radiation, chemicals, or errors during DNA replication.
Key Points to Remember
- Genes are units of inheritance
- They control the structure and function of cells through protein synthesis.
- Traits are passed from parents to offspring through genes.
- Mutations in genes can cause changes in traits.
- The expression of genes can be influenced by environmental factors.
Genes are the bridge between DNA and the traits we observe in living organisms. Understanding how they work is essential to studying heredity, genetic engineering, biotechnology, and evolution.