Like DNA, RNA is made up of nucleotides. There are two differences that distinguish DNA from RNA: (a) RNA contains the sugar ribose, while DNA contains the slightly different sugar deoxyribose (a type of ribose that lacks one oxygen atom), and (b) RNA has the nucleobase uracil while DNA contains thymine.
Why is every human genome different? Every human genome is different because of mutations—"mistakes" that occur occasionally in a DNA sequence. When a cell divides in two, it makes a copy of its genome, then parcels out one copy to each of the two new cells. These genome variations are uniquely yours.
There are four nucleotides, or bases, in DNA: adenine (A), cytosine (C), guanine (G), and thymine (T). These bases form specific pairs (A with T, and G with C).
DNA contains the instructions needed for an organism to develop, survive and reproduce. To carry out these functions, DNA sequences must be converted into messages that can be used to produce proteins, which are the complex molecules that do most of the work in our bodies.
Although each organism's DNA is unique, all DNA is composed of the same nitrogen-based molecules. So how does DNA differ from organism to organism? It is simply the order in which these smaller molecules are arranged that differs among individuals.
Normally, each cell in the human body has 23 pairs of chromosomes (46 total chromosomes). Half come from the mother; the other half come from the father. Two of the chromosomes (the X and the Y chromosome) determine your sex as male or female when you are born.
The diploid human genome is thus composed of 46 DNA molecules of 24 distinct types. Because human chromosomes exist in pairs that are almost identical, only 3 billion nucleotide pairs (the haploid genome) need to be sequenced to gain complete information concerning a representative human genome.
A human cell contains about 6 pg of DNA.
DNA is the material that carries all the information about how a living thing will look and function. DNA is short for deoxyribonucleic acid. It is in every cell of every living thing. DNA is found in structures of the cell called chromosomes. Both DNA and chromosomes are tiny.
DNA replication occurs in the cytoplasm of prokaryotes and in the nucleus of eukaryotes. Regardless of where DNA replication occurs, the basic process is the same. The structure of DNA lends itself easily to DNA replication. Each side of the double helix runs in opposite (anti-parallel) directions.
Complementary base pairing is important in DNA as it allows the base pairs to be arranged in the most energetically favourable way; it is essential in forming the helical structure of DNA. It is also important in replication as it allows semiconservative replication.
DNA, or deoxyribonucleic acid, is the hereditary material in humans and almost all other organisms. Nearly every cell in a person's body has the same DNA. DNA bases pair up with each other, A with T and C with G, to form units called base pairs. Each base is also attached to a sugar molecule and a phosphate molecule.
