2026 Skillsnap Learning Pvt. Ltd. All rights reserved.When we say a child "inherits" a trait from a parent, we mean that a piece of biological information passed from the parent's body into the baby's very first cell. That first cell is called a zygote — it forms the moment a sperm from the father meets an egg from the mother.
From that one tiny cell, every feature — your nose shape, your hair texture, even how tall you might grow — is already coded in. This coding is done by a special molecule called DNA.
Think of DNA as a very long instruction book written in a chemical language. This instruction book lives inside almost every cell of your body. It tells your body how to grow, what colour eyes to have, how your immune system should work, and thousands of other things.
A gene is just one specific section of that instruction book — one piece of instruction. For example, there is a gene that influences eye colour and another that affects your blood type.
DNA → the full instruction book | Gene → one chapter in that book | Chromosome → the shelf that holds the book
Humans have about 20,000 to 25,000 genes packed into their DNA. All this DNA is bundled up into structures called chromosomes, which sit inside the nucleus (control centre) of every cell.
Traits travel from parents to a baby through a fascinating biological system involving genes and DNA.
At the core is a concept called Genetics—the study of how characteristics are passed down. Each parent contributes half of the baby’s genetic material through reproductive cells (sperm and egg).
Inside these cells are structures called Chromosomes. Humans typically have 23 pairs of chromosomes (46 total), and each parent provides one chromosome for every pair. These chromosomes are made of DNA, which contains thousands of genes.
Genes are specific segments of DNA that control traits—like eye color, hair type, height, or even certain behaviors. For each trait, you usually inherit one version (called an allele) from each parent.
Some traits are:
Dominant: Only one copy is needed to show the trait (e.g., brown eyes often dominate over blue).
Recessive: You need two copies (one from each parent) for the trait to appear.
So if a baby gets:
One dominant allele + one recessive allele → dominant trait shows
Two recessive alleles → recessive trait shows
But it’s not always that simple. Many traits—like height, skin color, and intelligence—are influenced by multiple genes and environmental factors. This is called polygenic inheritance.
Also, sometimes traits can “skip” generations or combine in unexpected ways due to how genes interact.
Every human cell (except sperm and eggs) contains 46 chromosomes arranged in 23 pairs. One chromosome in each pair came from your mother, and the other came from your father.
Dominant vs. recessive traits — simple examples
For each gene, your body has two copies — one from your mum and one from your dad. These two copies may give the same instruction, or they may give different instructions. How does your body decide which one to follow?
This is where dominant and recessive genes come in:
Dominant Gene: If even one copy of this gene is present, it "wins" and its trait shows up. Example: dark hair is usually dominant over light hair.
Recessive Gene: This gene only shows up if both copies carry the same recessive instruction. Example: blue eyes are
generally recessive — a child usually needs two "blue eye" copies to have blue eyes.
So if a mother has dark eyes and carries one "blue eye" gene hidden inside, and the father also carries a hidden "blue eye" gene, there is a chance their child could have blue eyes — even though neither parent does!
The 23rd pair of chromosomes is special — it determines whether the baby will be biologically male or female. These are called the sex chromosomes.
Every egg the mother produces carries an X chromosome.
A sperm from the father carries either an X chromosome or a Y chromosome.
If an X sperm fertilises the egg → XX = girl
If a Y sperm fertilises the egg → XY = boy
Genes are not the only story. Even though your DNA is set from the moment of fertilisation, how genes are actually read and used can change based on what happens during pregnancy and throughout life.
This is called epigenetics — which simply means "on top of genetics." Things like a mother's nutrition, stress levels, exposure to pollution, and even her emotions can affect which genes in the baby get switched on or off.
So two identical twins with the exact same DNA can end up slightly different from each other because of their experiences and environment.
Traits are passed through genes carried in DNA. During fertilization, the mother’s egg and the father’s sperm combine, each contributing half of the genetic material to form the embryo.
2026 Skillsnap Learning Pvt. Ltd. All rights reserved.