recombination

Examples of recombination in the following topics:

• Biochemical Products of Recombinant DNA Technology

  • Many practical applications of recombinant DNA are found in human and veterinary medicine, in agriculture, and in bioengineering.
  • Recombinant DNA technology is the latest biochemical analysis that came about to satisfy the need for specific DNA segments.
  • Recombinant DNA technology engineers microbial cells for producing foreign proteins, and its success solely depends on the precise reading of equivalent genes made with the help of bacterial cell machinery.
  • Some of the recent advances made possible by recombinant DNA technology are:
  • Isolating proteins in large quantities: many recombinant products are now available, including follicle stimulating hormone (FSH), Follistim AQ vial, growth hormone, insulin and some other proteins.

• Generalized Recombination and RecA

  • In homologous recombination, a type of genetic recombination, nucleotide sequences are exchanged between two similar molecules of DNA.
  • Homologous recombination is a type of genetic recombination in which nucleotide sequences are exchanged between two similar or identical molecules of DNA.
  • Homologous recombination is conserved across all three domains of life as well as viruses.
  • Homologous recombination is a major DNA repair process in bacteria.
  • This type of resolution produces only one type of recombinant (non-reciprocal).

• Gene rearrangement within genomes

  • In meiosis and mitosis, recombination occurs between similar molecules (homologs) of DNA.
  • Genetic recombination and recombinational DNA repair also occurs in bacteria and archaea.
  • Recombination can be artificially induced in laboratory (in vitro) settings, producing recombinant DNA for purposes including vaccine development.
  • V(D)J recombination in organisms with an adaptive immune system is a type of site-specific genetic recombination that helps immune cells rapidly diversify to recognize and adapt to new pathogen.
  • Recombination can occur between DNA sequences that contain no sequence homology.

• Recombinant DNA Technology

  • Recombinant DNA technology also referred to as molecular cloning is similar to polymerase chain reaction (PCR) in that it permits the replication of a specific DNA sequence.
  • Most modern vectors contain a variety of convenient cleavage sites that are unique within the vector molecule (so that the vector can only be cleaved at a single site) and is located within a gene (frequently beta-galactosidase) whose inactivation can be used to distinguish recombinant from non-recombinant organisms at a later step in the process.
  • To improve the ratio of recombinant to non-recombinant organisms, the cleaved vector may be treated with an enzyme (alkaline phosphatase) that dephosphorylates the vector ends.
  • The creation of recombinant DNA is in many ways the simplest step of the molecular cloning process.
  • Therefore, recombinant clones are easily identified .

• Genetic Linkage and Violation of the Law of Independent Assortment

  • Genes that are on the same chromosome, or "linked", do not assort independently, but can be separated by recombination.
  • To understand this, let's consider the biological basis of gene linkage and recombination.
  • This process is called recombination, or crossover, and it is a common genetic process.
  • Because the genes are aligned during recombination, the gene order is not altered.
  • The result is two recombinant and two non-recombinant chromosomes.

• Genetic Linkage and Distances

  • Linked genes can become unlinked during recombination; the probability of genes separating depends on their distance from each other.
  • A recombination frequency of 0.5 indicates that 50 percent of offspring are recombinants and the other 50 percent are parental types .
  • The recombination frequency will be the same as if the genes were on separate chromosomes.
  • (d) The actual recombination frequency of fruit fly wing length and body color that Thomas Morgan observed in 1912 was 17 percent.
  • This genetic map orders Drosophila genes on the basis of recombination frequency.

• Genetic Maps

  • Linkage analysis involves studying the recombination frequency between any two genes.
  • The greater the distance between two genes, the higher the chance that a recombination event will occur between them, and the higher the recombination frequency between them .
  • Because genetic maps rely completely on the natural process of recombination, mapping is affected by natural increases or decreases in the level of recombination in any given area of the genome.
  • Some parts of the genome are recombination hotspots, whereas others do not show a propensity for recombination.
  • Recombination between genes A and B is more frequent than recombination between genes B and C because genes A and B are farther apart; a crossover is, therefore, more likely to occur between them.

• Selection

  • DNA recombination has been used to create gene replacements, deletions, insertions, inversions.
  • Subsequently, these fragments are then combined with vector DNA to generate recombinant DNA molecules.
  • The recombinant DNA is then introduced into a host organism (typically an easy-to-grow, benign, laboratory strain of E. coli bacteria).
  • This will generate a population of organisms in which recombinant DNA molecules are replicated along with the host DNA.
  • Thus, both the resulting bacterial population, and the recombinant DNA molecule, are commonly referred to as "clones".

• Genetic Engineering

  • In genetic engineering, an organism's genotype is altered using recombinant DNA, created by molecular cloning, to modify an organism's DNA.
  • Genetic engineering is the alteration of an organism's genotype using recombinant DNA technology to modify an organism's DNA to achieve desirable traits.
  • Recombinant DNA technology, or DNA cloning, is the process of transferring a DNA fragment of interest from one organism to a self-replicating genetic element, such as a bacteria plasmid, which is called a vector.
  • The addition of foreign DNA in the form of recombinant DNA vectors generated by molecular cloning is the most common method of genetic engineering.
  • The organism that receives the recombinant DNA is called a genetically-modified organism (GMO).

• Genetically Engineered Vaccines

  • Despite the early success demonstrated with the hepatitis B vaccine, no other recombinant engineered vaccine has been approved for use in humans.
  • Although recombinant subunit vaccines hold great promise, they do present some potential limitations.
  • In addition to being less reactogenic, recombinant subunit vaccines have a tendency to be less immunogenic than their conventional counterparts.
  • Recombinant subunit vaccines may also suffer from being too well-defined, because they are composed of a single antigen.
  • This problem can be minimized, where necessary, by creating recombinant vaccines that are composed of multiple antigens from the same pathogen.