01709 210151 / 07716 135940 kerry.leeson@alstrom.org.uk

Understanding Genetics

We often hear the words, Genes, DNA, Genetics, Genome Sequencing, banded around, like we know what the news reader or researcher is talking about… but do we really?

Let’s start at the beginning…

What is a Gene?

Genes play an important role in determining physical traits, such as how we look. They carry information that makes you who you are and what you look like: curly or straight hair, long or short legs, even how you might smile or laugh. Many of these things are passed from one generation to the next in a family by genes.

Genes carry the information that determines your traits , which are features or characteristics that are passed on to you, or inherited, from your parents. Each cell in the human body contains about 25,000 to 35,000 genes.

For example, if both of your parents have green eyes, you might inherit the trait for green eyes from them, or if your mom has freckles, you might have freckles too because you inherited the trait for freckles. Genes aren’t just found in humans, all animals and plants have genes, too.

Genes are found on tiny spaghetti-like structures called chromosomes and these are found inside cells. Your body is made of billions of cells. Cells are the very small units that make up all living things. A cell is so tiny that you can only see it using a strong microscope.

Chromosomes come in matching sets of two (or pairs) and there are hundreds , sometimes thousands of genes in just one chromosome. The chromosomes and genes are made of DNA, which is short for deoxyribonucleic acid.

Most cells have one nucleus, which is a small egg-shaped structure inside the cell which acts like the brain of the cell. It tells every part of the cell what to do. The nucleus has more information in it than the biggest dictionary you’ve ever seen.

In humans, a cell nucleus contains 46 individual chromosomes or 23 pairs of chromosomes. Half of these chromosomes come from one parent and half come from the other parent.

Under the microscope, we can see that chromosomes come in different lengths and striping patterns. When they are lined up by size and similar striping pattern, the first twenty two of the pairs these are called autosomes; the final pair of chromosomes are called sex chromosomes, X and Y. The sex chromosomes determine whether you’re a boy or a girl: females have two X chromosomes while males have one X and one Y.

How do Genes work?

Each gene has a special job to do. The DNA in a gene spells out specific instructions, 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. Those proteins help our bodies grow, work properly, and stay healthy. Scientists today estimate that each gene in the body may make as many as 10 different proteins. That’s more than 300,000 proteins!

Like chromosomes, genes also 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 color and skin color.

When there are problems with Genes

Scientists are very busy studying genes. They want to know which proteins each gene makes and what those proteins do. They also want to know what illnesses are caused by genes that don’t work right. Genes that have been changed are called mutations. Researchers think that mutations may be partly to blame for lung problems, cancer, and many other illnesses. Other illnesses and health problems happen when there are missing genes or extra parts of genes or chromosomes.

Some of these gene problems can be inherited from a parent. For example, take the gene that helps the body make hemoglobin. Hemoglobin is an important protein needed for red blood cells to carry oxygen throughout the body. If parents pass on altered hemoglobin genes to their child, the child might only be able to make a type of hemoglobin that doesn’t work properly. This can cause a condition known as anaemia, a condition in which a person has fewer healthy red blood cells. Sickle cell anemia is one kind of anemia that is passed on through genes from parents to children.

What is Gene Therapy?

Gene therapy is a new kind of medicine, so new that scientists are still doing experiments to see if it works. It uses the technology of genetic engineering to treat a disease caused by a gene that has changed in some way. One method being tested is replacing sick genes with healthy ones. Gene therapy trials, where the research is tested on people, and other research may lead to new ways to treat or even prevent many diseases.

Genomics England

Genomics England was set up to deliver the 100,000 Genomes Project.
This project will sequence 100,000 whole genomes from NHS patients with rare diseases, and their families, as well as patients with common cancers.

In October 2018, the Health Secretary Matt Hancock announced the expansion of the 100,000 Genomes Project to see 1 million whole genomes sequenced by the NHS and UK Biobank in five years and an ambitious vision for genomic medicine in the NHS – with plans to sequence 5 million genomes over the next five years.

Why sequence a genome?

Learning more about genomes can help us to identify the cause of genetic diseases.

Some rare diseases are caused by as little as a single change (variant), like a spelling mistake, in someone’s DNA. Looking at the genome of a person affected by a rare disease can help find which DNA changes might be causing the problem.

In cancer, the tumour cells have developed a different genome to the healthy cells. Comparing the normal and cancer genomes may give clues about ways to treat the cancer. Find out more about genomics and cancer.

For some patients, knowing more about their genome may mean that a particular treatment can be recommended.

When the genome sequences of patients with the same condition are compared, it is possible to see patterns. These patterns can be put together with health information. Once this is done we may be able to link particular patterns with whether people are likely to become ill and, if so, how severe their illness is likely to be.

What is a genome and how does genome sequencing work?
Find out in this short film courtesy of Great Ormond Street Hospital.

Further Information

If you would like to find out more about the work of Genomics England check out their website HERE

The Genomics Education Programme, offer some useful information on their website, including ‘Bitesize Genomics’ – you can find these resources HERE

The NHS provide further information about why you may be asked to have a genetic test, the impact on your family and how the data will be collected and used on the NHS website HERE

More information about the NHS England, National Genomic Test Directory, can be found HERE

The Government’s Strategy Genome UK: the future of health care can be found HERE