It was recently announced that 35 thousand new DNA samples were to be sequenced, or mapped out, to expand knowledge about the human genome. A "genome" is the entire set of DNA instructions inside every cell in every living thing.
A genome "sequence" is the complete list of the nucleotides (A, C, G, and T for DNA genomes) that make up all the chromosomes of an individual or a species. In humans, the majority of nucleotides are the same between individuals, that's the part that makes us humans and not dogs or bacteria, right?
Think about it, every cell in your body has the complete code inside of it to make another you! We all started from just two cells, one from a father and one from a mother, and together they made a brand new person.
Human cells have 23 pairs of chromosomes (22 pairs of "autosomes" and one pair of sex chromosomes), giving a total of 46 per cell. In addition to these, human cells have many hundreds of copies of the mitochondrial genome. The autosomal DNA is found in the nucleus, and the mitochondrial DNA is found outside of the nucleus in the cell structure.
Each chromosome has genes on it, the number varies from chromosome to chromosome 1 - 22 and for the 23rd x and y sex chromosomes. Chromosome #21 has the fewest genes at 200 with 46,944,323 base pairs, and the largest is #19 with 63,806,651 base pairs of nucleotides. The whole human genome consists of 21,000 genes with 3,079,843,747 base pairs. That's 3 BILLION pieces of code in each cell!
That 23rd chromosome is passed down through every generation. The Y chromosome is passed on from father to son and the X chromosome is passed from mother to daughter. The data from those two sex chromosomes can be traced back over one hundred of thousand years!
The latest news in genomes is about additional DNA being sampled from additional areas of Africa and Neanderthal DNA recovered from fossils. The new models from the gene mapping suggest that we humans came from multiple ancestral populations around Africa that lived over a million years ago. These different populations are believed to have inbred and moved apart from each other over time. I'll include a link to the Nature study at the bottom of the page so you can take a look later, if you like.
It may not be just one tree of life, as we thought just a few weeks ago, but a tangled vine! The human machine is a marvelous thing. We are all the same, but at the same time, we are all different, due to our individual DNA mixtures. Isn't it amazing that we share common ancient ancestors?
Even as we have migrated, evolved, developed new languages, customs, and religions, we are still all related to each other at the most basic level.
Look around yourself and wonder at world of living things all made of carbon based atoms and organized at the microcellular level into different life forms! And at that microcellular level in humans is the coding that tells that cell whether it is a kidney cell, or a blue or brown eye cell, or a hair cell!
Only 97% of our 3 billion+ base pairs have been mapped at last count. Scientists hope that the new sequencing initiative announced recently will result in more information about those unmapped areas. The answers to preventing cancer and birth defects may soon be found if scientists can rub the Gene Genie's magic lamp in the right way.
Speaking of Y chromosomes, Father's Day is coming soon! DNA kits should be back on sale soon, so watch for the ads. I have met some lovely people over the last couple of weeks, and I would love to chat with you too. Always a free look at your tree to see if I could help, just let me know with an email!
Best wishes for a week full of wonderment,
Leslie Ryan
No compensation is received for any links or references in here.
No copyright infringement is intended. Tip of the hat to David Bowie for the article title.
Link for Nature.com news article about the latest genome study: https://www.nature.com/articles/d41586-023-01664-z