It's estimated that one in 25 children has a genetic condition of some sort, varying in severity.
Some of the conditions are inherited from both parents, others from just one, and some can occur spontaneously as a new genetic event in a child.
Anna Whaite, a Genetic Disorders UK genetic counsellor, shares what she believes everybody should know about genetic disorders....
1. Genes and genetic disorders vary wildly
Some genetic disorders are apparent at birth, while others are diagnosed at different stages throughout childhood, and even into adulthood sometimes. Whaite explains that we all carry thousands of genes (made of DNA and carried on chromosomes inherited from our parents), which are instructions for how our bodies grow and function.
"The exact code of our genes varies from person to person, which is why we're all different," she says. "If someone has an alteration which disrupts a gene, that can cause a genetic disorder."
While some genetic disorders are quite common, others are incredibly rare, and can range from being mild to devastating and life-threatening. They can affect any part of a person, such as vision, hearing, bone growth, skin formation, muscles and more. Some genetic disorders are obvious, altering appearance, growth and mobility, while others cause symptoms that aren't easy to see from the outside, affecting internal organs, thinking processes or metabolism, for instance.
2. We can't change our genes
Once a genetic disorder has been diagnosed, there may be treatments and interventions available to help manage the symptoms, but sometimes there's no medication that can help.
"Living with the disorder can add a huge strain on an individual's and a family's day-to-day life," says Whaite. "We can't simply switch a gene off, take it out, or mend it if it doesn't work properly, although gene therapy and other research continues to improve options for the future."
3. Chromosome changes can cause some genetic disorders
While many genetic disorders are caused by changes in single genes, others are due to changes to chromosomes, the structures that carry genes. For example, Down's syndrome is caused by having an extra copy of chromosome 21, instead of the usual two.
Other chromosome changes can mean parts of a chromosome are deleted or duplicated, or sometimes swapped around. This can have a significant effect on development and can sometimes be detected during pregnancy scans.
4. Gender matters
Some genetic disorders affect males and females differently, particularly if they're X-linked (caused by a change in a gene found on the X chromosome). This is because females have two 'X' chromosomes and males have one 'X' and one 'Y' chromosome.
If there's a genetic change in a gene on the 'X' chromosome, for example with Duchenne muscular dystrophy - an X-linked condition - a male would show symptoms of this. "A female with the same gene change may have only mild symptoms or no problems at all," explains Whaite, "as she has another X which would be healthy and helps to compensate for the other X."
5. Some inherited disorders are still a mystery
While many genetic tests are available to make or confirm a diagnosis, there are some inherited disorders that can't yet be detected by a gene test.
Hypermobile Ehlers Danlos syndrome is one example of a condition that can't be diagnosed by a genetic test, as the gene or genes involved aren't fully understood.
Whaite says: "Huge scientific efforts, like The Human Genome Project and related schemes, have completed a map of the entire human genome (all of the genetic material on a living thing's chromosomes), but it will take many more years to find out what each gene does and how they interact with one another."
6. Genetic disorders aren't always inherited
Some genetic disorders run in families and have been around for generations, like Huntington's disease (which causes the progressive degeneration of nerve cells in the brain, affecting movement, cognition and behaviour). But others happen when two healthy carriers have a child with a genetic disorder - cystic fibrosis, for example.
Some occur due to a new spontaneous change in the DNA sequence of a gene, called a de novo mutation, which can happen around conception. "This is not because of anything anyone has done or not done, and these kinds of diagnoses can come as a huge shock," says Whaite.
7. Chance has no memory
When someone with a genetic disorder has children, the chance the disorder will be passed on is the same for each pregnancy. If a recurrence risk of a genetic disorder is 50%, this risk is the same each time a baby is conceived - it doesn't mean that if the first child is affected ,the next will automatically be OK.
"Some families can seem to be 'lucky', others less so, but the risks remain the same each time - chance has no memory," Whaite stresses. Different conditions have different recurrence risks, which can be discussed during genetic counselling.