In either case, this relieves or ‘relaxes’ the strain, one twist at a time.
#HEAVY LIFING ATP FREE#
Then the uncut strand is free to pass through the break. Type I topoisomerase cuts one of the DNA strands and temporarily bonds to both ends of the cut. There are several classes of topoiso-merases, but they are grouped into two main types: They must work ahead of the replication fork to keep the DNA from over-winding. 3 They cut the DNA, rearrange it, and stick it back together. The Creator solved this problem in living creatures with special protein machines (enzymes) called topoisomerases. Disclaimer: This is a simple diagram of a very intricate piece of machinery. This process is paramount to all life as we know it. DNA replication or DNA synthesis is the process of copying a double-stranded DNA molecule. In a cell, if the DNA were prevented from unwinding, then the cell could no longer make proteins or copy itself. To compensate for every added twist in the forward direction, the DNA behind the unwinding site adds a twist, and also becomes supercoiled (overwound). If you let go, the rope will tend to coil back upon itself-think also of the coiled cords on older telephones which too easily become tangled into coils upon coils. It will soon become too hard to unwind because of the resistance of the extra twists on both sides of the separation point. You can easily demonstrate the problem with a long multi-stranded rope: start in the middle and try to pull the strands apart. SupercoilsĭNA’s helical (coiled) shape produces another problem that is amplified when helicase unwinds it to separate the strands. This must run very fast, because the DNA copying speed is 1,000 letters per second and the helicase must stay ahead of the copying machines. 2 Then, many other machines take care of decoding the DNA and putting the strands back together or copying the strands. The helicase rapidly runs along the DNA and separates the two strands at the replication fork. 1 Using ATP as an energy source, a cyclic change in shape runs around the helicase ring at about 10,000 rpm-about the speed at which a jet engine turbine rotates. Helicases are powered by a ‘fuel’ called ATP, which is made by another motor, ATP-synthase. But, since they are motors, they also need fuel. They are ring-shaped, with a hole for the DNA to pass through. This requires special motors called DNA helicases. And during reproduction, each strand is copied independently. When DNA is decoded (that is, when the information is used to create a protein), the two strands of the double helix must be separated. These machines are amazing, complex, and a testimony to the genius of our Creator. The cell needs complex machines to do all this. If all the DNA in your cell were lined up, it would be about 2 m (6–7 feet) long! These enormously long, thin, sticky strands must be packed into a microscopic cell and then maintained without forming a mess of tangles and knots. But the whole DNA molecule is extremely long: the largest human chromosome, number 1, is composed of 220 million letters, and would be 85 mm (3.4 in) long if stretched out fully. A complete turn of the helix is about 10.5 letters long. The double helix is only about 2.5 nanometres (one ten-millionth of an inch) wide-too thin to be seen with any light microscope (visible light has a wavelength 380&ndash700 nm). You didn’t really get your mother’s eyes and father’s ears rather, it was the instructions to re-manufacture your mother’s eyes and father’s ears that were copied to your DNA (see box below).ĭNA’s physical dimensions pose many problems that would need to be solved before even the simplest life could function. DNA’s physical dimensions pose many problems that would need to be solved before even the simplest life could function.įurthermore, these instructions are copied to the next generation.
#HEAVY LIFING ATP MANUAL#
This manual comprises sequences of chemical ‘letters’ (nucleotides) in the famous deoxyribonucleic acid (DNA) molecule, just as information in a book is written in letters on a page. God’s DNA-detangling motors The topoisomerase enzymesĪll living creatures contain incredible machines, as well as the ‘instruction manual’ to build them.
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