What is Genome?
The word genome refers to all DNA present in an organism. The DNA is the “Genetic Blueprint” that determines the genotypic make-up of each organism. DNA consists of two strings of nucleotides, or bases (abbreviated A, C, G, and T), wound around each other. The bases composing DNA have specific binding capabilities: A always binds to T, and C always binds to G. These binding capabilities are useful for scientists to understand since, if the nucleotide sequence of one DNA strand is determined, complementary binding allows the sequence of other strand to be deduced.
In humans, DNA is organized into 24 structural units called chromosomes. Each chromosome consists of compacted coils of DNA. While much of this DNA has no known function (these stretches of DNA are conveniently referred to as spacer DNA or junk DNA), a significant portion of the DNA codes for genes.
Each gene provides the information necessary to produce a protein, which is responsible for carrying out cellular functions. The complement of proteins in an organism is very important, with diseases often manifesting when a protein does not function properly.
Why Sequence Genomes? Why do we sequence non-human genomes?
One of the interesting things about biological organisms is their remarkable similarity at the molecular level, despite their obvious outward differences.
Many genes are found in morphologically different organisms despite the phylogenetic distance between them. Not only are these genes very similar in their DNA sequence composition; they also tend to perform the same functions.
By understanding the function of a gene in one organism, scientists can get an idea of what function that gene may perform in a more complex organism such as humans. The knowledge gained can then be applied to various fields such as medicine, biological engineering and forensics.
To understand how DNA is sequenced, you must first understand a little about the structure of DNA:
A segment of DNA, which is ordinarily double stranded, has a specific orientation, as it has a 5′ (read as “5 prime”) and a 3′ (”3 prime”) end. This can be simply thought of as a front and tail end to the DNA segment.
When DNA is synthesized in the lab, the two strands are separated and new bases are added to the 3′ end-thus DNA is assembled from the 5′ to 3′ end.
When DNA is synthesized in the lab, the two strands are separated and new bases are added to the 3′ end-thus DNA is assembled from the 5′ to 3′ end.
DNA cannot be synthesized from scratch. A short piece of DNA, called a primer, is required for the reaction to begin.
Primers are designed such that they are able to bind to the target DNA, the binding of which is the initiator for DNA synthesis.
Primers are designed such that they are able to bind to the target DNA, the binding of which is the initiator for DNA synthesis.
DNA sequencing is accomplished by the Fredrick Sanger method (see the above diagram), for which he won his second Nobel Prize in 1980.
Below is a diagram of a non human DNA sequencing.. .the sequence of a cave bear:
The Human Genome Project
The HGP or Human Genome Project was a 13-year project by the U.S. Department of Energy and the National Institutes of Health. During. The goals were to identify all the approximately 20,000-25,000 genes in human DNA, determine the sequences of the 3 billion chemical base pairs that make up human DNA, store this information in a genome databases, improve tools for data analysis, transfer related technologies to the private sector, and address the ethical, legal, and social issues that may arise from these type of projects.
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