The determination of the entire DNA sequences of numerous ancient species, including woolly mammoths (see below), Neanderthals, and a 700,000-year-old horse, has been accomplished in the recent decade or two.

The sequencing of the human genome, which was basically finished in 2003, was critical to those findings. This project was a watershed moment in biology because it spurred significant technological advancements in DNA sequencing.

The first human genome sequence took several years and cost one billion dollars; since then, the time and cost of sequencing a genome have been in free fall. A simulation of a sequencing process in which the nucleotides of a single strand of DNA are sequenced with tiny changes in an electrical current.

• The term DNA Technology refers to the main techniques for sequencing and manipulating DNA

DNA sequencing and cloning are useful tools for genetic engineering and biological research. The discovery of the structure of the DNA molecule, especially the understanding that its two strands are complementary to each other, paved the way for the development of DNA sequencing and other techniques that are now employed in biological study.

Nucleic acid hybridization, the base matching of one strand of a nucleic acid to a corresponding sequence on a strand from a separate nucleic acid molecule, is central to these methods. The key approach in genetic engineering is direct gene modification.

Researchers may use the complementary base pairing principle to identify the full nucleotide sequence of a DNA molecule, a technique known as DNA sequencing. The DNA is first broken into pieces, which are then sequenced one by one. Dideoxyribonucleotide (or dideoxy) chain termination sequencing was utilized in the first automated method.

One strand of a DNA fragment is utilized as a template for the synthesis of a nested set of complementary fragments, which are then examined to produce the sequence.

Frederick Sanger, a biochemist, was awarded the Nobel Prize in 1980 for discovering this approach. Dideoxy sequencing is still utilized for small-scale sequencing tasks on a regular basis.

As nucleic acids or proteins travel in an electric field, a polymer gel functions as a molecular sieve to separate them based on size, electrical charge, or other physical characteristics. In this example, as shown in the image attached above, DNA molecules are separated by a length in a gel comprised of agarose, a polysaccharide.

As shown in the image attached above, Figure 20.5, the most effective restriction enzymes break the sugar-phosphate backbones in the two DNA strands in a staggered way.

The resultant double-stranded restriction fragments have at least one single-stranded end, which is referred to as a sticky end. These small extensions have the ability to create hydrogen-bonded base pairs with corresponding sticky ends on any additional DNA molecules cut with the same enzyme.

These transient connections can be made permanent by DNA ligase, which catalyzes the creation of covalent bonds that shut up the sugar-phosphate backbones of DNA strands.

To test the recombinant plasmids after many copies in host cells (as shown in the image attached), a researcher may cut the products again with the same restriction enzyme, anticipating two DNA fragments, one the size of the plasmid and one the size of the inserted DNA.

To separate and visualize the fragments, researchers employ gel electrophoresis, a method that uses a polymer gel as a molecular filter to separate a mixture of nucleic acid fragments by length. In molecular biology, gel electrophoresis is employed in combination with a variety of methods.

PCR is the most popular method for obtaining numerous copies of the gene to be cloned.

DNA technology, particularly the study of genetic markers such as SNPs, is increasingly being utilized in the diagnosis of genetic and other diseases, and it holds the promise of better treatment of genetic disorders or perhaps permanent cures via gene therapy or gene editing with the CRISPR-Cas9 system. It also allows for better-educated cancer treatments.

DNA technology is used with cell cultures to produce protein hormones and other therapeutic proteins on a big scale.

Transgenic “pharm” animals are being used to generate some therapeutic proteins. The detection of genetic markers such as short tandem repeats (STRs) in DNA extracted from tissue or bodily fluids collected at crime scenes leads to a geological investigation. Transplanting the nucleus of a developed animal cell into an enucleated egg can occasionally result in the birth of a new animal.

Certain embryonic stem cells (ES cells) derived from animal embryos and specific adult stem cells derived from adult tissues can multiply and develop both in the lab and in the organism, suggesting medicinal applications.

Pluripotent ES cells are difficult to get. In their ability to develop, induced pluripotent stem (iPS) cells are similar to ES cells; they may be produced by reprogramming differentiated cells. iPS cells have great potential in medical research and regenerative medicine.

DNA microarrays are used to identify groups of genes that are expressed by the same group of cells. Instead, RNA sequencing (RNA-seq) is increasingly being utilized to sequence the cDNAs that correlate to RNAs from cells.

When a gene's function is unknown, experimental inactivation of the gene (a gene knockout) and observation of the resultant phenotypic consequences might give information.

The CRISPR-Cas9 technology enables researchers to precisely alter genes in live cells. The new alleles can be modified such that they are passed down in a biased manner through a population (gene drive).