Why does having a extra or one less chromosome have such an impact on the body


Why does having a extra or one less chromosome have such an impact on the body

In: 4

Chromosomes are responsible for your genetic code, thus they are also responsible for your looks.
When you have an additional chromosome it messes up your genetic code, and causes physical and mental disproportions.

Edit: I’ve brought this off of a quick Google research and it was a pretty interesting read, thanks for encouraging me to look it up

Bio refresher: you have 23 pairs of chromosomes numbered in decreasing size except the last two which are the sex chromosomes XY or XX. Each chromosome is a wrapped up strand of DNA encoding genes.

If you’re baking a cake but add half as much of some ingredients or too much of some ingredients there will be problems with the final cake.

Gene regulation is tightly regulated, but it is set up for 2 of each chromosome (with the exception of sex chromosomes which are a bit more complex). If you have one more or one less chromosome the genes on them will be expressed in the wrong amounts which can be catastrophic.

In fact it’s often lethal which is why most cases of an extra chromosome happen with the smallest chromosomes. An extra copy of chromosome 21 (smallest somatic chromosome) causes down syndrome, an extra copy of the larger 13 or 18 are lethal within the first year of life, most other trisomy’s would result in miscarriages. Missing a whole chromosome is almost always lethal. The exception is turner syndrome (a woman missing one X) which is only survivable because women mostly “turn off” one of their x chromosomes. It’s not fully off which is why turner syndrome has symptoms but it’s close enough that its not lethal.

DNA is like computer code. If a part of the codes get missing you can’t perform the functions that were dependant on the lost code. Which causes the program (organism) to fail.

Same with an extra part of the code. You might ask for value x from a but you get value x from b. Which might cause the rest of the program to fail. But for some rare cases like down syndrome it is not that big of disaster that you fail completely.