New nucleotides move in to each side of the unzipped ladder. The bases on these nucleotides are very particular about what they connect to. Cytosine C will "pair" to guanine G , and adenine A will "pair" to thymine T. How the bases are arranged in the DNA is what determines the genetic code. Each contains one side of the original DNA and one side made of "new" nucleotides. It is possible that mistakes were made along the way -- in other words, that a base pair in one DNA molecule doesn't match the corresponding pair in the other molecule.
The arrangement of these bases is very important as this determines what the organism will be — a plant, an animal, or a fungus. This is called genetic coding. It is twisted to the right, making the shape of the DNA molecule a right-handed double helix.
In fact, if you lined up each molecule of DNA in one cell end to end, the strand would be six feet in length. When it is time to replicate, the hydrogen bonds holding the base pairs together break, allowing the two DNA strands to unwind and separate. The specific base pairing provides a way for DNA to make exact copies of itself.
Each half of the original DNA still has a base attached to its sugar-phosphate backbone. It reads the original strand and matches complementary bases to the original strand. New strands attach to both sides of the original DNA, making two identical DNA double helices composed of one original and one new strand. Please note that the above explanation of DNA replication is highly simplified.
All living things — plants, animals, and humans — pass DNA from parents to offspring in the form of chromosomes. In humans, 23 chromosomes are passed on from the mother and 23 chromosomes are passed on from the father, giving the child 46 chromosomes. For each child, different sets of genes are passed on from the parents, resulting in unique DNA for each child.
This means that even though the genetic code for all human beings is Knowing this, DNA can be used to identify people in a variety of situations. This field is known as forensic science. DNA is often used to solve crimes by identifying victims and suspects while at the same time ruling out innocent people as possible suspects for a crime.
It is also used to prove or disprove family relationships, identify missing persons, and identify the victims of catastrophes who are no longer physically identifiable. And since DNA can be found in a variety of human tissues and fluids such as hair, urine, blood, semen, skin cells, bones, teeth, and saliva, it greatly aids in identification when other methods, such as fingerprints and teeth structure, are no longer usable.
The medical field also uses DNA. Now that doctors at least partially understand how DNA works, modern medicine has made advances in identifying diseases and finding cures.
Many diseases, like cystic fibrosis, are hereditary diseases, meaning they are passed on from parent to offspring. By looking at the DNA of an individual, doctors can determine what the disease is or how susceptible a person or their children are to having a particular disease. Doctors also study how cells with damaged DNA multiply to help them find cures or treatments for diseases such as cancer and tumors. But knowledge of DNA is not just used in humans. Food scientists use DNA information to improve crops and develop new food sources.
Plant breeders select plants that produce high yields of food, are resistant to pests, and tolerate environmental stresses better than similar plant varieties. C bonds to G by three hydrogen bonds. A bonds to T by two hydrogen bonds. A and G are double ringed structures called "purines".
C and T are single ringed structures called "pyramidines".
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