Structural Biochemistry/Genome Analysis
The purpose of genomics research has been the sequencing and analysis of the human genome. The human genome is made up of about 3 billion base pairs of DNA, which are distributed among 24 chromosomes. This poses the difficulty of producing a complete sequence. By going through the process of an organized international effort of academic labs and private companies, though, the human genome has now progressed from a draft sequence which was first reported in 2001 to a finished sequence in 2004.
The human genome contains a plethora of information about the different characteristics of humanity, including biochemistry and evolution. Analysis of the human genome will continue to grow and expand in order to better understand humans. One of the first tasks in accomplishing this is to develop an inventory of protein-encoding genes. When the genome-sequencing project first began, about 100,000 genes were estimated to exist. When the completed, but unfinished, genome was first made available, this estimate actually dropped down to about 30,000 to 35,000 genes. It dropped again to 20,000 to 25,000 when the sequence was finished. Because there are a relatively large number of pseudogenes, many of which are formerly functional genes that have mutated and are no longer expressed, the estimate of genes dropped by 75%. More than half of the genomic regions for olfactory receptors, the molecules responsible for the human sense of smell, are pseudogenes. The surprisingly small number of genes still belies the complexity of the human proteome, though. Many genes encode more than one protein through mechanisms such as alternative splicing of mRNA and posttranslational modifications of proteins. Important variations in functional properties are shown in the different proteins encoded by a single gene.
A large amount of DNA is contained in the human genome that does not participate in the coding of proteins. Modern-day biochemists and genetic researchers are attempting to elucidate the roles of this noncoding DNA, as a lot of this DNA shows due to the existence of mobile genetic elements. These elements have inserted themselves throughout the genome over the course of time. Most of these elements, though, have gone through mutations and, therefore, are no longer functional. More than 1 million Alu sequences, each sequence consisting of about 300 bases, are present in the human genome. Alu sequences are examples of SINES, short interspersed elements. Additionally, the human genome includes nearly 1 million LINES, long interspersed elements, which are DNA sequences that are 10 kilobase pairs in length. The roles of these elements as neutral parasites or instruments of genome evolution are still being studied.
The exploration of genes relies on key tools 1. Restriction-enzyme analysis 2. Blotting techniques 3. DNA sequencing 4. Solid-phase synthesis of nucleic acids 5. The Polymerase chain reaction
Comparative Genomics[edit | edit source]
Insight into the human genome can be discovered by comparing it with the genomes of other organisms. For example, the sequencing of the genome of chimpanzees, the closest living relative to humans, is almost complete. Genomic comparisons with other mammals used in biological research, such as mice and rats, have already been completed. The results of these comparisons show that 99% of human genes have counterparts in these rodent genomes. These genes, however, have been greatly reassorted among chromosomes in the estimated 75 million years of evolution since humans and rodents have had a common ancestor. The genomes of other organisms has been determined specifically for the purpose of comparative genomics. When comparing the genomes of various other organisms with human genomes, more than 1000 formerly unrecognized human genes are revealed. Furthermore, comparative genomics is a powerful tool for both interpreting the human genome as well as understand major events in the origin of genera and species.