Genetic inheritance Genes come with a backup copy because we inherit chromosomes from each of our parents. When our body makes eggs or sperm, one of each pair of our chromosomes is randomly put into each egg or sperm cell. When an egg and sperm cell join (fertilisation) the new baby will get one of each pair from each parent. This means we have two copies of every chromosome from chromosome 1 to chromosome 23. The 23rd pair of chromosomes determines our biological sex with females having two of the bigger X chromosomes (one from each parent) and males having one X (inherited from Mum) and one smaller Y chromosome (inherited from Dad). Epidermolysis Bullosa is caused by any one of many different genetic changes in several different genes that cause broken versions of skin proteins like keratin or collagen to be produced. Different types can be inherited in a dominant or recessive way and you may want to discuss genetic testing with your care team if you are planning a family. If you have a family member who is living with EB but you have no symptoms and are planning to start a family, you may choose to discuss genetic testing with your care team or GP to see if you might be a ‘carrier’.