By Meenambika Menon
What decides the colour of our eyes and makes members of the family look similar?
A person’s eye colour results from pigmentation of a structure called the iris, which surrounds the small black hole in the centre of the eye (the pupil). Eye colour is determined by variations in a person’s genes. Most of the genes associated with eye colour are involved in the production, transport, or storage of a pigment called melanin. Eye colour is directly related to the amount and quality of melanin in the front layers of the iris. People with brown eyes have a large amount of melanin in the iris, while people with blue eyes have much less of this pigment.
Members of the same family look similar because of the same gene pool they belong to. Children look like combinations of their parents because they are. Each parent gives half of their genetic material to their children. Properties or traits are passed from parents to children and so on.
How do genes work? Can you give an example?
Genes have DNA (de oxy ribonucleic acid). The DNA spells out specific instructions — much like in a cookbook recipe — for making proteins in the cell. Proteins are the building blocks for everything in your body. Bones and teeth, hair and earlobes, muscles and blood, are all made up of proteins.
Genes come in pairs. Each of your parents has two copies of each of their genes, and each parent passes along just one copy to make up the genes you have. Genes that are passed on to you determine many of your traits, such as your hair colour, skin colour, eye colour, etc.
For example, Raima’s mother who has one gene for blue eyes and one gene for brown eyes passes the gene of brown eyes to Raima. If her father has two genes for brown eyes and passes one to Raima, Raima will have brown eyes.
What is gene therapy?
Gene therapy is an experimental technique that uses genes to treat or prevent disease. Researchers are testing several approaches to gene therapy, including:
- Replacing a mutated gene that causes disease with a healthy copy of the gene.
- Introducing a new gene into the body to help fight a disease.
- Gene therapy is currently being tested only for diseases that have no other cures.
What are cells and who tells them what to do?
A cell is the building block of an organism. A group of similar cells makes tissues, tissues make organs, organs make the organ system and systems make organisms.
The different types of cells in your body have different, specialised jobs to do. For example, nerve cells can be very long, which makes them efficient in sending signals from the brain to the rest of your body, cells in heart muscle process a lot of energy, etc.
Cells have a nucleus. This is the cell’s control centre. The nucleus, which contains DNA, tells the cells what to do. The DNA is like a computer with loads of information stored and encoded so if something is needed then that section of DNA is copied and made into a protein.
What makes a dinosaur a dinosaur and a mosquito a mosquito?
Their genetic make is responsible for their body characteristics. It is believed that the first form of life which photosynthesised on Earth was blue green algae. Every life form present today evolved from that. The genes regulated, adapted and formed cells which perform different functions. From single celled organisms, multicellular complex organisms evolved.
How can you explain DNA to a child? Why is DNA so important and why is it called an instruction manual?
DNA is the genetic code that determines all the characteristics of a living thing. Basically, your DNA is what makes you, you!
We get our DNA from our parents and call it ‘hereditary material’. Nobody else in the world will have DNA the same as you, unless you have an identical twin.
DNA is a record of instructions telling the cell what its job is going to be. DNA is like a set of blueprints for the cell, or computer code telling a PC what to do. It is written in a special alphabet that is only four letters long! These letters are A, T, C and G. Unlike a book or computer screen, DNA isn’t flat and boring; it is a beautiful curved ladder. We call this shape a double helix. DNA is made up of nucleotides, which have a phosphate and sugar group and nitrogen bases (A, T, C and G).
Think of all the words you can spell. Each word you can spell is made using the same selection of letters. Depending on how we arrange the letters of the alphabet we can make new words. The same is true in the four letter alphabet of DNA. Each series of words tells a cell to make a special molecule called a protein. These proteins control everything in a cell.
(Source: Some inputs have been sourced from kidshealth.org, ghr.hlm.nih.gov and owlcation.com.)
(Meenambika Menon is Lead, Curriculum – Science & Math at Shiv Nadar School.)