I am currently working through a FutureLearn on ‘the genomics era’. The course introduced some of the genetic errors that can happen in certain diseases.
One of the errors occurs when cells divide to form reproductive cells (sperm or eggs) – a process called meiosis. Most cells in the body have 46 chromosomes, arranged in 23 pairs. Reproductive cells have half the number, so that when a sperm and egg fuse, the newly fertilised cell has the normal complement of 46.
Certain diseases, like Down syndrome, Edwards syndrome and Patau syndrome, are the result of an extra chromosome in the fertilised egg. So instead of 23 pairs, there are 22 pairs and one triplet (or ‘trisomy‘). This error occurs when the reproductive cells are made, if the chromosomes of the parent cell are unevenly split between two new daughter cells.
The course featured a moving video of two parents whose daughter was diagnosed with Down syndrome. The father explains a powerful analogy to capture the emotions and experience of being told of such a diagnosis. The essay, ‘Welcome to Holland’ written in 1987 by Emily Perl Kingsley about having a child with a disability, is narrated in the video below, and is incredibly touching.