Fast Facts about Human Genetics
1. DNA stands for Deoxy-ribo-Nucleic Acid.
2. On February 28, 1953, Francis Crick and James Watson figured out the structure of deoxyribonucleic acid (DNA). That structure, a 'double helix', can "unzip" (separate into two long strands) to make copies of itself. This discovery confirmed suspicions that DNA carried an organism's hereditary information.
3. DNA molecules are linked, one after another, like pearls on a very long string.
4. DNA molecules are the "software" that direct cellular activity and determine everything about an organism - from what it looks like to how long it is likely to live. Genes are pieces of this DNA, and are the fundamental units of heredity.
5. The complete human genome consists of approximately 3 billion DNA molecules.
6. On average, each chromosome has about 65 million DNA molecules.
7. A gene is a stretch of DNA molecules (ranging in length from thousands to tens of thousands of DNA molecules, in some cases they may be even larger).
8. Between genes, along the length of a chromosome, there may be long stretches of DNA, which have no known function.
9. A chromosome contains about 1000 genes.
10. Humans have approximately 30,000 different genes spread out over the 46 chromosomes.
11. Humans get one complete set of genes from each parent.
12. In April 2003, the National Human Genome Research Institute (NHGRI) celebrates the completion of the human genome sequence and the 50th anniversary of the description of the DNA double helix.
13. The nucleus, or control centre, of a cell, is where the DNA is coiled up into chromosomes. With the exception of reproductive cells, every cell has 46 chromosomes. Twenty-two pairs of the chromosomes are similar in terms of size, shape and genetic content. The twenty-third pair determines the sex of the individual, and is composed of either two x chromosomes (female) or an x and a y chromosome (male).
14. DNA molecules are incredibly long. If all of the DNA from all of your cells was stretched out into a single thread, it would extend to the moon and back about one million times!
15. It takes about eight hours for one of your cells to completely copy its DNA.
16. The human DNA code is made up of about three thousand million A,T, C, and Gs on each side of the DNA strand.
17. If you were to start reciting the order of the ATCGs in your DNA tomorrow morning, at a rate of 100 each minute, 57 years would pass before you reached the end (provided that you did not stop to eat, drink, sleep, use the bathroom etc.)
18. If you were to stretch out the DNA from those 46 chromosomes in one cell and lay it end to end, it would be over 2 yards in length.
19. If the total DNA in one person were laid in a straight line, it would stretch to the sun and back over 30 times (it’s 93 million miles from here to the sun).
20. You could fit one thousand nuclei across the period at the end of this sentence.
21. You could fit one million threads of DNA across the period at the end of this sentence.
22. Humans are 99.9% genetically identical - only 0.1% of our genetic make-up differs.
23. Information, and yet, all of it is contained inside the microscopic nucleus of a cell so tiny that it could easily fit on the head of a pin!
24. Our genes are remarkably similar to those of other life forms. For example, we share 98% of our genes with chimpanzees, 90% with mice, 85% with zebra fish, 21% with worms, and 7% with a simple bacterium such as E. coli.
25. Less than 2% of the total DNA carries instructions to make proteins. The rest is misleadingly called ‘junk’ DNA, because it is a hodge-podge of sequences that does not seem to code for anything.
