િહશે ેપછૂ ્, ુાં ‘તનેતારી િા નથી િારતી ....’ ખાલી જગ્યાિાાં કયુાં મવરાિબચહ્ન આવે?
(A) , (B) ? (C) !
this language is Gujarati.
please u understand stand then answer me. fast.
ok
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Answer:
Smithsonian National Museum of Natural HistoryThe Smithsonian Institution's Human Origins Program
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DNA and Evolution
WHAT IS DNA?
DNA, or deoxyribonucleic acid, is a molecule found in the nuclei of cells. DNA contains genes, the building blocks of all organisms.
THE STRUCTURE OF DNA
The most important function of DNA is its ability to replicate itself repeatedly. DNA must be copied when new cells are formed, when genetic material is passed from parents to offspring, and when coding for RNA (ribonucleic acid) to make proteins. The structure of DNA – a double helix – allows DNA to be copied successfully many times over with very few errors.
DNA’s double helix (which looks like a twisted ladder) is made of units called nucleotides. Each nucleotide consists of a phosphate, sugar, and base. The phosphates and sugars form the sides of the ladder, while the bases form the rung. A base from a nucleotide on one side of the ladder will chemically bond with a nucleotide from the other side, forming the rung. Certain bases always pair together; adenine always pairs with thymine and guanine always pairs with cytosine. These four bases have different chemical structures, causing them to pair in this specific manner.
When DNA replicates, the bonds between bases break and the DNA “unzips” itself. New nucleotides are joined to either side of the broken ladder by the work of DNA polymerase, an enzyme. Enzymes are proteins that mediate and initiate chemical reactions. When the polymerase has traveled the entire length of the DNA, it will have formed two new ladders from the original single ladder. Now the DNA has been perfectly copied from one strand into two. Some enzymes will even “proofread” the DNA to try to catch any errors!