What is meant by genetic difference?

Looking around you, it’s hard to escape the fact that people are all very different in the way we look, how tall we are, our hair and eye colour. You might also have noticed that within
families we often share features or traits with brothers, sisters, parents, aunts and
uncles. But have you ever thought about just how much is down to your genes? Bill was born on 15th November 2001. His gender was determined by the inheritance of a single gene, from his father. This gene was passed on to Bill within
a chromosome. Chromosomes are made up of long strands of genes and come in pairs. Humans have 46 chromosomes in 23 pairs. Just one pair is used to determine a person’s gender. Bill has one Y and one X chromosome. It is the Y chromosome that carries a gene which determined his gender. His y chromosome is inherited from his father, who inherited his Y from his father and so on… But if his father had passed on the X chromosome instead, then Bill would have been a girl! This is an example of a genetic trait. However, it’s not always this clear cut… Some traits are down to a mixture of traits from both parents. Sarah was born on 8th July 2002. Her blood group is determined by the genes of both parents. You get a mixture of genes from your parents, half from mum and half from dad, but unless you are an identical twin, you’ll actually have a different mix of your parents genes to your brothers and sisters. In this case Bill is both a different gender and a different blood group to Sarah because they each inherited a different mixture of their parent’s genes. In fact most things are actually determined by many genes … these include eye and hair colour. Sometimes many different genes combine in order to influence a trait. For example, height is likely to be determined by the combined influence of over 100 genes. One example is the HMGA2 gene; depending upon which version of it you have, it could be adding as much as 0.4cm to your height! Think of all those small contributions from lots of genes and you can see how we are all different
heights. However, if your family all carry a set of genes that are all likely to add up to being tall, then being tall will be passed
onto the family. But certain genetic traits like height can
be influenced by more than your genes… You’ve probably heard of the balance between Nature and Nurture. Whilst genes influence almost everything in your body, the environment you grow up in can also make a big difference. Your genes provide the key to your potential height, but this is only realised if you get sufficient nutrition. Understanding the role that genetics play in our health and wellbeing is important, as it can help us determine the cause of various
diseases or conditions. But how do we know how much a trait is influenced by our genes?

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