Tuesday, June 30, 2020

HUMAN GENOME PROJECT

Human Genome

In 1990, researchers at Celera Genomics and at the National Human Genome Research Institute began an ambitious endeavor to sequence the entire human genome. In 2003, the project was completed, resulting in the sequencing of all human chromosomes. The Human Genome Project revealed that the human genome contains only 20,000 to 25,000 genes. This estimation, based on the sequence data, is substantially below previous predictions. The sequence data has led to the estimation that only about 1 percent of the human genome actually encodes functional proteins. Once the jigsaw puzzle is completed, the data will undoubtedly help researchers devise new diagnostics and treatments for genetic diseases.

Human Genomic Variation

In addition to sequencing the human genome, researchers have sequenced the genomes of Drosophila melanogaster (fruit fly), Arabidopsis thaliana (plant), Saccharomyces cerevisiae (budding yeast), and C. elegans (worm). In addition, mouse, rat, and zebrafish genomes have been sequenced. Eukaryotic organisms are also useful to the research community. The genome of Plasmodium (the organism that causes malaria) has also been sequenced. The goals of these sequencing projects are to prepare gene linkage maps and physical maps. A gene linkage map pinpoints the location of genes based on their connection to certain marker gene sequences. A physical map, in comparison, gives the actual number of bases between genes on a chromosome; therefore, it locates the gene of interest more precisely.

Beyond the Human Genome | National Institutes of Health (NIH)

Ultimately, scientists hope to learn the actual names and sequences of all 3 billion nitrogenous base pairs in the human genome. Automation and computerization are essential tools in the sequencing, and the development of the specific technology is underway.

BIOTECHNOLOGY TOOLS

Tools of Biotechnology

The basic process of recombinant DNA technology involves manipulating an organism’s DNA and thus altering the proteins being produced (see Chapter 10). During this synthesis, DNA provides the genetic code for the placement of amino acids in proteins. By intervening in this process, scientists can change the nature of the DNA, thereby changing the nature of the protein expressed by that DNA. By inserting genes into the genome of an organism, the scientist can induce the organism to produce a protein it does not normally produce.

The technology of recombinant DNA has been made possible in part by extensive research on microorganisms during the last half-century. One important microorganism in recombinant DNA research is Escherichia coli, commonly referred to as E. coli. The biochemistry and genetics of E. coli are well known, and its DNA has been isolated and made to accept new genes. The DNA can then be forced into fresh E. coli cells, and the bacteria will begin to produce the proteins specified by the foreign genes. Such altered bacteria are said to have been transformed.

Biotechnology Research Tools | Drug Testing | Microbiome Research ...

Knowledge about viruses has also aided the development of DNA technology. Viruses are fragments of nucleic acid surrounded by a protein coat. Viruses attack cells and replicate within the cells, thereby destroying them. By attaching DNA to viruses, scientists use viruses to transport foreign DNA into cells and to connect it with the nucleic acid of the cells.

Another common method for inserting DNA into cells is to use plasmids, which are small loops of DNA in the cytoplasm of bacterial cells. Working with a plasmid is much easier than working with a chromosome, so plasmids are often the carriers, or vectors, of DNA. Plasmids can be isolated, recombined with foreign DNA, and then inserted into cells where they multiply as the cells multiply.

PPT - More Basic Biotechnology Tools PowerPoint Presentation, free ...

Interest in recombinant DNA and biotechnology heightened considerably during the 1960s and 1970s with the discovery of restriction enzymes. These enzymes catalyze the opening of a DNA molecule at a “restricted” point, regardless of the source of the DNA. Figure shows that a human DNA molecule is opened at a certain site by the restriction enzyme EcoRI (upper left), and the desired DNA fragment is isolated (lower left). Plasmid DNA is treated with the same enzyme and opened. The DNA fragment is spliced into the plasmid to produce the recombinant DNA molecule.

 

Construction of a recombinant DNA molecule.

Certain restriction enzymes leave dangling ends of DNA molecules at the point where the DNA is opened. Foreign DNA can therefore be combined with the carrier DNA at this point. An enzyme called DNA ligase forges a permanent link between the dangling ends of the DNA molecules at the point of union.

Benefits & Risks of Biotechnology - Future of Life Institute

Recombinant DNA technology is sophisticated and expensive. Genes must be isolated, vectors must be identified, and gene control must be maintained. Stability of the vector within a host cell is important, and the scientist must be certain that nonpathogenic bacteria are used. Cells from mammals can be used to synthesize proteins, but cultivating these cells is difficult. In addition, the proper gene signals must be identified, RNA molecules must be bound to ribosomes, and the presence of introns must be considered. Collecting the gene product and exporting it from the cell are other considerations.

The genes used in DNA technology are commonly obtained from host cells or organisms called gene libraries. A gene library is a collection of cells identified as harboring a specific gene. For example, E. coli cells can be stored with the genes for human insulin in their chromosomes.

STEM CELLS AND THEIR CLONING

Cloning and Stem Cells

Cloning refers to the ability to make a genetic replica of a cell (or even an entire organism, also called reproductive cloning). Interest in cloning is due primarily to its potential to create stem cells. A stem cell is a cell that has not yet differentiated and retains the ability to turn into many different tissues. Stem cells have enormous potential in medical applications because they can be used to replace diseased or damaged tissues and aid in organ repair or replacement.

Does the Source of a Stem Cell Change Its Properties?

In order for reproductive cloning to work, a differentiated cell must “dedifferentiate,” allowing it to access the genes for any given cell type. This cell can then give rise to all the specialized cell types of an organism. One source of undifferentiated stem cells is from early-stage embryos. Considering the ethical implications of embryonic stem (ES) cells, research has begun to focus on adult stem cells. Adult stem cells are found in a number of tissues, including dental pulp, bone marrow, and the brain. These cells, however, are not able to differentiate into all cell types and thus are not as beneficial as embryonic stem cells.

Cloning Fact Sheet

In 2007, researchers announced their successful reprogramming of fully differentiated adult cells, thus inducing an ES-cell state. These induced pluripotent stem (iPS) cells can do everything an ES cell can do without the ethical implications associated with embryonic cells.

BIOMOLECULES CHEMISTRY CLASS 12

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