KS3 Science Revision
Inheritance
Your body is full of cells, each containing a nucleas. Inside this nucleas is something called chromosones. Chromosones come in pairs and are usually twisted and coiled up. These strands of chromosones are called DNA. They are chemical instructions on how to build a human. Everyone's chromosones are different. Everyone has 23 pairs of chromosones in their body (46 chromosones.) This is because you inherit 23 from your mother and 23 from you father. Each sperm and egg contain 23 chromosones, ready to be attached to another 23 through fertilisation.
You can inherit two sets of genes from your parents. For example: one parent may have blue eyes and the other brown. In this case, the dominant gene is in charge. Brown eyes is dominant over blue eyes so you will have blue eyes. Since your parents also have a pair of chromosones, it is 50/50 which chromosone you will get. This also means that you could inherit a disease carried down the family.
In this diagram, the dominant gene is displayed with a capital letter. D is a disease. If a baby has one D from dad and one d from mum, then it will have the disease because D is the dominant gene.