linkage disequilibrium

Examples of linkage disequilibrium in the following topics:

• No Perfect Organism

  • Alleles that are carried together are in linkage disequilibrium.

• Genetic Linkage and Violation of the Law of Independent Assortment

  • The segregation of alleles into gametes can be influenced by linkage, in which genes that are located physically close to each other on the same chromosome are more likely to be inherited as a pair.
  • To understand this, let's consider the biological basis of gene linkage and recombination.
  • Mendel's seminal publication makes no mention of linkage, and many researchers have questioned whether he encountered linkage, but chose not to publish those crosses out of concern that they would invalidate his independent assortment postulate.
  • However, even if the genes he examined were not located on separate chromosomes, it is possible that he simply did not observe linkage because of the extensive shuffling effects of recombination.

• DNA and RNA

  • The phosphate residue is attached to the hydroxyl group of the 5′ carbon of one sugar and the hydroxyl group of the 3′ carbon of the sugar of the next nucleotide, which forms a 5′3′ phosphodiester linkage.
  • The phosphodiester linkage is not formed by simple dehydration reaction like the other linkages connecting monomers in macromolecules: its formation involves the removal of two phosphate groups.
  • A polynucleotide may have thousands of such phosphodiester linkages.

• Genetic Maps

  • The study of genetic maps begins with linkage analysis, a procedure that analyzes the recombination frequency between genes to determine if they are linked or show independent assortment.
  • The term linkage was used before the discovery of DNA.
  • The mapping of genes relative to each other based on linkage analysis led to the development of the first genetic maps.
  • Linkage analysis involves studying the recombination frequency between any two genes.

• Carbohydrate Molecules

  • Glycosidic bonds (also called glycosidic linkages) can be of the alpha or the beta type.
  • In sucrose, a glycosidic linkage is formed between carbon 1 in glucose and carbon 2 in fructose.
  • In cellulose, glucose monomers are linked in unbranched chains by β 1-4 glycosidic linkages.

• Genetic Linkage and Distances

• Dehydration Synthesis

  • In nucleic acids and proteins, the location and stereochemistry of the covalent linkages connecting the monomers do not vary from molecule to molecule, but instead the multiple kinds of monomers (five different monomers in nucleic acids, A, G, C, T, and U mononucleotides; 21 different amino acids monomers in proteins) are combined in a huge variety of sequences.

• Intercellular Junctions

  • It is created by the linkage of cadherins and intermediate filaments.

• Connecting Other Sugars to Glucose Metabolism

  • Sucrose is a disaccharide with a molecule of glucose and a molecule of fructose bonded together with a glycosidic linkage.

• Protein Structure

  • Cysteine side chains form disulfide linkages in the presence of oxygen, the only covalent bond forming during protein folding.
  • The tertiary structure of proteins is determined by hydrophobic interactions, ionic bonding, hydrogen bonding, and disulfide linkages.