When you make a baby you make someone who is half their Mum, half their Dad and one hundred percent unique. But how does this happen? Why do some children look like their Dad or have hair just like their Mum? This all comes down to how you pass on your own genetic information to your children.
WHAT IS GENETIC INFORMATION?
Genetic information, or DNA, is in every single cell in your body. It can be thought of as a book of instructions that your cells use to be able to do their job. Your DNA tells a muscle cell how to behave like a muscle or a brain cell how to behave like a brain cell. Your DNA also tells your eyes, skin and hair what colour they should be.
DNA is wrapped up into packages called chromosomes. These are like chapters in a book. Every person has two identical sets of 23 chromosomes. This means that every instruction is repeated, it is like having an extra copy of the instruction book just in case there is a page missing or a mistake.
You also have two chromosomes that control whether you are a man or a woman. These are called your sex chromosomes, but are also referred to as the X and Y chromosome because of their shape. Men have an X and a Y chromosome, women have two X chromosomes.
PASSING ON GENETIC INFORMATION: HOW DOES IT HAPPEN?
When you have children they get a mix of instructions. One set of the chromosomes comes from the mother, and the other set from the father. This happens during a process called fertilisation, when the sperm from the man meets the egg from the woman.The egg and sperm only have one set of chromosomes. A baby cannot be made by just the male sperm or the female egg, the DNA from both is necessary to make a healthy baby.
When the sperm and egg come together at fertilisation the fathers set of chromosomes mixes with the mothers set of chromosomes and creates a completely new set of instructions. A girl is created when the X chromosome from the mother is mixed with the X chromosome from the father. A boy is created with the X chromosome from the mother is mixed with the Y chromosome from the father.
WHY MIX UP GENETIC INFORMATION?
This mixing of mothers and fathers DNA means that the DNA is strong. Mistakes can happen in DNA, but mixing up two separate sets means that the chances of these mistakes causing diseases is much less. This is because many of the mistakes require two copies to cause disease. This would mean the mother and the father would have to have the same mistake. This does happen, but it would happen more often if the mother’s and father’s DNA were not mixed up.
Some genetic features are stronger than others. For example the genetic code for brown eyes is stronger than the one for blue eyes. If one parent has blue eyes and one has brown it is more likely that a child will have brown eyes. The stronger genetic feature can come from the mothers or the fathers DNA. Sometimes there are mistakes that mean a child may have a medical condition. This is not anyone’s fault. It is important that children born with mistakes in their genetic material get medical care and support.