GCSE Biology: What are Genes?

Frank Ivins

March 19, 2014

As part of National Science & Engineering Week, one of  Tutorfair’s top Biology tutors, Frank I, explains how to get to grips with the GCSE Biology topic: genetic engineering. As Frank has a PhD in this specialism and has previously worked in the lab for Cancer Research, he certainly knows his stuff! His first blog post in this series on genetic engineering explains what genes actually are; not your standard Levi’s!

Genetic engineering. Thanks to decades of film and TV, it’s a term that conjures images of extreme deformity like Godzilla and Spiderman. Though the reality isn’t quite as crazy, the current and future impact of genetic engineering on each of us and and especially our children is, and will be, HUGE—Godzilla huge.

As a species, human beings have been practising genetic engineering for thousands of years, though for most of that time we didn’t know it. From the moment the first tribe of hunter-gatherers settled down and realized that breeding the best wheat plants or the best cows together gave them even better wheat and better cows, human study into genetic engineering began. Today, we don’t just breed our crops and animals to get what we want, we pick genes from one species and pop them into another—the ‘Frankenstein’ experiments we’ve all heard about.

DNA Biology
Let’s back up. Before we can explain what genetic engineering is, I suppose we should get clear on just what a gene is. Genes, DNA, chromosomes, the nucleus—we lump them all together in our heads and that’s fine, because they are just different ways of looking at the same thing.  Chromosomes are just separate chunks of DNA, living in a bag inside the cell, called the nucleus.  If we read along each chromosome, we can divide it up into segments called genes, and there are thousands of them in each and every cell!

So what is this DNA stuff that makes up our genes? Well, if you asked someone off the street they would probably say that DNA controls the cell and is responsible for our physical characteristics like eye colour or height.  And they’d be right!  But how exactly does DNA do this?  DNA holds the instructions for what a cell should be doing. For example: the cells of a baby growing in a pregnant mother are instructed to divide rapidly; a muscle cell is instructed to contract; and a nerve cell is told to send an electrical impulse to the brain.

Think of DNA as the boss of a busy factory (the cell) sitting high in an office shouting orders down to thousands of workers busy building and assembling a car.  DNA doesn’t actually do any of the work—the workers do!  And each worker is different from all the other workers.  Each worker is specialized to build one and only one part of the whole car, but each does its job very well.  In our cell, those workers are proteins.

Proteins come in many different shapes and sizes: long and thin, spherical, ball-and-chain, and loads more.  Like snowflakes, no two are identical.  No two protein shapes are alike and no two jobs for our workers to do are alike.  And each of us can make about 30,000 different shapes, each with a different job!  Like our workers in the car factory where one is great at making the transmission while another is fantastic at making the steering wheel—one protein (insulin) helps us control our blood sugar while another uses a blast of energy to spring forward and contract our muscles.  Different cells like brain cells or heart cells use a different mix of protein workers to do their jobs.

Not only does the lazy DNA not do any of the actual work, DNA doesn’t even MAKE the workers.  Little protein-making machines far, far from the nucleus do that job.  DNA simply holds the information for HOW to make the proteins.

So how does this all actually work?  Well, I’m all typed out.  Shall we meet back here later for part 2?

If you have found this blog post helpful, you might also find Frank’s previous blog post explaining photosynthesis useful.

If you or your child needs help with Biology or you fancy private tuition then please view Frank’s personal profile on the Tutorfair website to book a lesson.