When mutations are passed down from parent to child, we call it inheritance. The type of mutation, and where it occurs in the genome can influence the probability that it will be inherited.
To explore this, we must first understand how our genome is created.
The creation of a new genome
DNA is stored in densely packed structures called chromosomes. There are 23 pairs of chromosomes in a cell – so 46 in total. This is true for each type of cell in your body, bar one – your gametes.
An individual will make one of two kinds of gametes – sperm, or ova (eggs). Gametes have only 23 chromosomes, one from each pair, and are made through a process called meiosis. During meiosis, the pairs of chromosomes swap chunks of DNA with one another in a process called crossover, thus making a new, random assembly of DNA. These new chromosomes then split into separate gamete cells, to be inherited by the individuals offspring.
Upon fusion of a sperm and ovum, a zygote is created. Each of the gamete’s 23 chromosomes will find its pair, creating a new 46 chromosome genome. The zygote then starts dividing rapidly, creating exact copies of this new genome that will go on to form life.