Courtesy : Bachelor of Science Biology (CBZ) – Chemistry, Botany, Zoology Book

Genomes

Further information: Genomics

Composition of the human genome

A genome is an organism’s complete set of DNA, including all of its genes. Sequencing and analysis of genomes can be done using high throughput DNA sequencing and bioinformatics to assemble and analyze the function and structure of entire genomes.  The genomes of prokaryotes are small, compact, and diverse. In contrast, the genomes of eukaryotes are larger and more complex such as having more regulatory sequences and much of its genome are made up of non-coding DNA sequences for functional RNA (rRNA, tRNA, and mRNA) or regulatory sequences. The genomes of various model organisms such as arabidopsis, fruit fly, mice, nematodes, and yeast have been sequenced. The Human Genome Project was a major undertaking by the international scientific community to sequence the entire human g3enome, which was completed in 2003. The sequencing of the human genome has yielded practical applications such as DNA fingerprinting, which can be used for paternity testing and forensics. In medicine, sequencing of the entire human genome has allowed for the identification of mutations that cause tumors as well as genes that cause a specific genetic disorder. The sequencing of genomes from various organisms has led to the emergence of comparative genomics, which aims to draw comparisons of genes from the genomes of those different organisms.e.# ISO certification in India

Many genes encode more than one protein, with posttranslational modifications increasing the diversity of proteins within a cell. An organism’s proteome is its entire set of proteins expressed by its genome and proteomics seeks to study the complete set of proteins produced by an organism. Because many proteins are enzymes, their activities tend to affects the concentrations of substrates and products. Thus, as the proteome changes, so do the amount of small molecules or metabolites. The complete set of small molecules in a cell or organism is called a metabolome and metabolomics is the study of the metabolome in relation to the physiological activity of a cell or organism.# ISO certification in India

Biotechnology

Main article: Biotechnology

Construction of recombinant DNA, in which a foreign DNA fragment is inserted into a plasmid vector

Biotechnology is the use of cells or organisms to develop products for humans.  One commonly used technology with wide applications is the creation of recombinant DNA, which is a DNA molecule assembled from two or more sources in a laboratory. Before the advent of polymerase chain reaction, biologists would manipulate DNA by cutting it into smaller fragments using restriction enzymes. They would then purify and analyze the fragments using gel electrophoresis and then later recombine the fragments into a novel DNA sequence using DNA ligase. The recombinant DNA is then cloned by inserting it into a host cell, a process known as transformation if the host cells were bacteria such as E. coli, or transfection if the host cells were eukaryotic cells like yeast, plant, or animal cells. Once the host cell or organism has received and integrated the recombinant DNA, it is described as transgenic.# ISO certification in India

A recombinant DNA can be inserted in one of two ways. A common method is to insert the DNA into a host chromosome, with the site of insertion being random.  Another approach would be to insert the recombinant DNA as part of another DNA sequence called a vector, which then integrates into the host chromosome or has its own origin of DNA replication, thereby allowing to replicate independently of the host chromosome. Plasmids from bacterial cells such as E. coli are typically used as vectors due to their relatively small size (e.g. 2000–6000 base pairs in E. coli), presence of restriction enzymes, genes that are resistant to antibiotics, and the presence of an origin of replication. A gene coding for a selectable marker such as antibiotic resistance is also incorporated into the vector. Inclusion of this market allows for the selection of only those host cells that contained the recombinant DNA while discarding those that do not. Moreover, the marker also serves as a reporter gene that once expressed, can be easily detected and measured.# ISO certification in India

Once the recombinant DNA is inside individual bacterial cells, those cells are then plated and allowed to grow into a colony that contains millions of transgenic cells that carry the same recombinant DNA. These transgenic cells then produce large quantities of the transgene product such as human insulin, which was the first medicine to be made using recombinant DNA technology.# ISO certification in India

One of the goals of molecular cloning is to identify the function of specific DNA sequences and the proteins they encode. For a specific DNA sequence to be studied and manipulated, millions of copies of DNA fragments containing that DNA sequence need to be made. This involves breaking down an intact genome, which is much too large to be introduced into a host cell, into smaller DNA fragments. Although no longer intact, the collection of these DNA fragments still make up an organism’s genome, with the collection itself being referred to as a genomic library, due to the ability to search and retrieve specific DNA fragments for further study, analogous to the process of retrieving a book from a regular library. DNA fragments can be obtained using restriction enzymes and other processes such as mechanical shearing. Each obtained fragment is then inserted into a vector that is taken up by a bacterial host cell. The host cell is then allowed to proliferate on a selective medium (e.g., antibiotic resistance), which produces a colony of these recombinant cells, each of which contains many copies of the same DNA fragment. These colonies can be grown by spreading them over a solid medium in Petri dishes, which are incubated at a suitable temperature. One dish alone can hold thousands of bacterial colonies, which can be easily screened for a specific DNA sequence. The sequence can be identified by first duplicating a Petri dish with bacterial colonies and then exposing the DNA of the duplicated colonies for hybridization, which involves labeling them with complementary radioactive or fluorescent nucleotides.# ISO certification in India