Chromosomes Explained Simply
A chromosome is the tightly packaged form your DNA takes inside every cell. If DNA weren't wound up this tightly, it would never fit inside the tiny nucleus.
One chromosome pair - one inherited from each parent. Humans have 23 such pairs.
đź’¬ Mia asks Grandpa Theo
What's the actual difference between a chromosome, DNA, and a gene? They all sound the same to me.
Think of it like a book: DNA is the entire text. A gene is a single chapter with one specific set of instructions. And a chromosome is a whole, tightly bound volume containing many genes in a row.
Why do they always come in pairs instead of single chromosomes?
Because you get one copy of every chromosome from your mother and one from your father. So for each of your 23 chromosomes, you have two versions - one maternal, one paternal.
Is one of the 23 pairs special in some way?
Yes, pair number 23 - the sex chromosomes. In the other 22 pairs, both chromosomes look very similar to each other, but in pair 23, the combination of X and X or X and Y determines whether an egg cell or a sperm cell is produced.
Sometimes an error occurs during cell division and a chromosome ends up present three times instead of two. For chromosome 21, this is called trisomy 21, or Down syndrome - a well-known example of how much a single extra chromosome can affect development.
Doctors can make a person's chromosomes visible under a microscope and sort them by size - that's called a karyotype, and it lets certain genetic conditions be spotted directly.
← Back to overview