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Biology LibreTexts

Unit 11: Genomics

  • 11.1: Recombinant DNA and Gene Cloning
    Recombinant DNA is DNA that has been created artificially. DNA from two or more sources is incorporated into a single recombinant molecule.
  • 11.2: Polymerase Chain Reaction
    The polymerase chain reaction is a technique for quickly "cloning" a particular piece of DNA in the test tube (rather than in living cells like E. coli). Thanks to this procedure, one can make virtually unlimited copies of a single DNA molecule even though it is initially present in a mixture containing many different DNA molecules.
  • 11.3.1: Gene Therapy - Methods and Prospects
    Many human diseases are caused by defective genes that are caused by a defect at a single gene locus. (The inheritance is recessive so both the maternal and paternal copies of the gene must be defective.) Is there any hope of introducing functioning genes into these patients to correct their disorder? Probably. Other diseases also have a genetic basis, but it appears that several genes must act in concert to produce the disease phenotype.
  • 11.3.2: Recent Advances in Gene Therapy
    Reaching the goal of effective gene therapies for human diseases has been a difficult one.
  • 11.4: Transgenic Animals
    A transgenic animal is one that carries a foreign gene that has been deliberately inserted into its genome. The foreign gene is constructed using recombinant DNA methodology. In addition to the gene itself, the DNA usually includes other sequences to enable it to be incorporated into the DNA of the host and to be expressed correctly by the cells of the host.
  • 11.5: Transgenic Plants
    Progress is being made on several fronts to introduce new traits into plants using recombinant DNA technology. The genetic manipulation of plants has been going on since the dawn of agriculture, but until recently this has required the slow and tedious process of cross-breeding varieties. Genetic engineering promises to speed the process and broaden the scope of what can be done.
  • 11.6: Restriction Fragment Length Polymorphisms
    Restriction Fragment Length Polymorphisms (RFLPs) have provided valuable information in many areas of biology, including screening human DNA for the presence of potentially deleterious genes ("Case 1") and providing evidence to establish the innocence of, or a probability of the guilt of, a crime suspect by DNA "fingerprinting" ("Case 3")
  • 11.7: Gel Blotting
    Gel blotting is a technique for visualizing a particular subset of macromolecules — proteins, or fragments of DNA or RNA — initially present in a complex mixture.
  • 11.8: Genetic Screening for Phenylketonuria
    Phenylketonuria is one of the commonest inherited disorders — occurring in approximately 1 in 10,000 babies born in the U. S. It occurs in babies who inherit two mutant genes for the enzyme phenylalanine hydroxylase (PAH — "1" in the figure on the left). This enzyme normally starts the process of breaking down molecules of the amino acid phenylalanine that are in excess of the body's needs for protein synthesis.
  • 11.9: Antisense RNA
    Messenger RNA (mRNA) is single-stranded. Its sequence of nucleotides is called "sense" because it results in a gene product (protein). Normally, its unpaired nucleotides are "read" by transfer RNA anticodons as the ribosome proceeds to translate the message.
  • 11.10: Antisense Oligodeoxynucleotides and their Therapeutic Potential
    Antisense oligonucleotides are synthetic polymers. The monomers are chemically-modified deoxynucleotides like those in DNA or ribonucleotides like those in RNA. There are usually only 15–20 of them, hence "oligo". Their sequence (3′ → 5′) is antisense; that is, complementary to the sense sequence of a molecule of mRNA.
  • 11.11: Forward and Reverse genetics
    Since Mendel's time, most genetics has involved observing an interesting phenotype tracking down the gene responsible for it. So this "forward" genetics proceeds from phenotype -> genotype. But now with a knowledge of the DNA sequence of a gene of unknown function, one can use methods for suppressing that particular gene ("knockdown"), and then observe the effect on the phenotype. So this "reverse" genetics proceeds from genotype -> phenotype.
  • 11.12: Metagenomics
    All the genomes listed on my page Genome Sizes describe the complete genome of a single species. For bacteria and archaeons, this means that the organism was grown in pure culture to provide the DNA for sequencing. But it is now clear that the microbial world contains vast numbers of both groups that have never been grown in the laboratory and thus have escaped study. Soil, water, and the contents of our large intestine are examples of habitats that teem with unknown microorganisms.

Thumbnail: A DNA microarray. Image used with permission (CC BY-SA 3.0; Guillaume Paumier).