DNA is a nucleotide polymer, or polynucleotide. Each nucleotide contains three components: A five carbon sugar A phosphate molecule A nitrogen-containing base. The sugar carbon atoms are numbered 1 to 5.
The nitrogenous base attaches to base 1, and the phosphate group attaches to base 5. DNA polymers are strings of nucleotides. Cells build them from individual nucleotides by linking the phosphate of one nucleotide to the 3 carbon of another. The repeating pattern of phosphate, sugar, then phosphate again is commonly referred to as the backbone of the molecule. The sugar in DNA is deoxyribose.
This missing hydroxyl group plays a role in the three-dimensional structure and chemical stability of DNA polymers. There are two groups of bases: Pyrimidines : Cytosine and Thymine each have a single six-member ring.
Purines : Guanine and Adenine each have a double ring made up of a five-atom ring attached by one side to a six-atom ring. DNA polymers can be tens of millions of nucleotides long. At these lengths, the four-letter nucleotide alphabet can encode nearly unlimited information. Nucleosides are similar to nucleotides, except they do not contain a phosphate group.
Without this phosphate group, they are unable to form chains. The second chain contains 11 nucleotides, also truncated after ddGTP addition. After complete analysis with all four ddNTPs, the final nucleotide sequence is shown in the right panel. Nucleotides are represented by different colored rectangles: red for thymine, blue for guanine, green for adenine, and orange for cytosine.
Below the sequenced strand, examples of truncated strands from the four reactions are shown. Reading the sequence: Now and then. How is DNA sequencing used by scientists? In recent years, DNA sequencing technology has advanced many areas of science.
For example, the field of functional genomics is concerned with figuring out what certain DNA sequences do, as well as which pieces of DNA code for proteins and which have important regulatory functions. An invaluable first step in making these determinations is learning the nucleotide sequences of the DNA segments under study. Another area of science that relies heavily on DNA sequencing is comparative genomics, in which researchers compare the genetic material of different organisms in order to learn about their evolutionary history and degree of relatedness.
DNA sequencing has also aided complex disease research by allowing scientists to catalogue certain genetic variations between individuals that may influence their susceptibility to different conditions. How can all people benefit from DNA sequencing? More about sequencing.
DNA sequencing technologies Sequencing the human genome. Watch this video for a summary of the Sanger sequencing process. How much does gene sequencing cost? How was the human genome sequenced? What happens during DNA replication?
Who, exactly, discovered DNA? How has the polymerase chain reaction PCR revolutionized biotechnology? What has genomics done for the biofuel industry? What ethical problems does DNA sequencing raise? How is sequencing done on a large scale? Who was Frederick Sanger? Key Concepts Human Genome Project bioinformatics genome. Topic rooms within Genetics Close.
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