Question: how many sorts of DNAs are there
Keywords: dna
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Hi disease357.
All DNA is made up of the same basic building blocks call nucleotides. These can be either an A, T, C or G. When the two opposite strands of DNA meet the nucleotides pair together and C always pairs with G and T always pairs with A. Because of this we say the two strands are ‘complementary’.
Now, what can change with DNA is the length of the strands, how many strands we have and whether they are linear or circular. The strands of DNA are packaged into what we call chromosomes. This is our DNA wrapped around proteins.
In humans we have 23 pairs of chromosomes which are linear. Bacteria have 1 chromosome which is circular. Fruit flies have 8 which are linear and pigeons have 80! You can see it varies quite a lot between different species.
Aside from chromosomes bacteria can carry an extra piece of DNA called a plasmid. Plasmids are small circular pieces of DNA and the number of copies of the plasmid in the bacteria can vary. Bacteria can also transfer the plasmid to other bacteria which don’t have one. Sometimes the plasmids carry the genes for antibiotic resistance. When one bacteria then starts transferring this they can make a population resistant very quickly. Plasmids are also commonly used in the lab for research because of the way we can transfer them into cells.
Some viruses also use DNA to carry their genetic material (the alternative is RNA). They don’t have it packaged into chromosomes or as a plasmid. It sits free inside the virus until they infect something and begin to replicate.
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