What's the difference between homology and similarity?

Homology


Definition:

  • (n.) The quality of being homologous; correspondence; relation; as, the homologyof similar polygons.
  • (n.) Correspondence or relation in type of structure in contradistinction to similarity of function; as, the relation in structure between the leg and arm of a man; or that between the arm of a man, the fore leg of a horse, the wing of a bird, and the fin of a fish, all these organs being modifications of one type of structure.
  • (n.) The correspondence or resemblance of substances belonging to the same type or series; a similarity of composition varying by a small, regular difference, and usually attended by a regular variation in physical properties; as, there is an homology between methane, CH4, ethane, C2H6, propane, C3H8, etc., all members of the paraffin series. In an extended sense, the term is applied to the relation between chemical elements of the same group; as, chlorine, bromine, and iodine are said to be in homology with each other. Cf. Heterology.

Example Sentences:

  • (1) Trifluoroacetylated rabbit serum albumin was 5 times more reactive with these antibodies and thus more antigenic than the homologous acetylated moiety confirming the importance of the trifluoromethyl moiety as an epitope in the immunogen in vivo.
  • (2) The ORF2 showed homology with the Escherichia coli regulatory gene ompR, and ORF4 showed homology with E. coli and Rhizobium meliloti regulatory genes fnr and fixK, respectively.
  • (3) Nucleotide sequence analysis of cDNAs for asparagine synthetase (AS) of Pisum sativum has uncovered two distinct AS mRNAs (AS1 and AS2) encoding polypeptides that are highly homologous to the human AS enzyme.
  • (4) In four main regions the conservation varied from 83-91% while in the remaining regions the homology dropped to between 56-62%.
  • (5) It has 61% homology with tRNA(Leu)(anticodon m5CAA) and 63% homology with tRNA(Leu)(anticodon UAG), the two other known yeast tRNAs(Leu).
  • (6) The specified region of the inner E2 core domain was highly homologous to the region of the E2 subunit of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase.
  • (7) This novel mechanism of receptor regulation, named transmodulation, should be distinguished from the reduction in total receptor number caused by the homologous ligand (downregulation) and from the change in affinity produced by the binding of agonists or antagonists to the same receptor site.
  • (8) This unusual insertion could affect the interaction of cat CD4 with class II molecules, or with FIV, a feline homolog of HIV.
  • (9) On the basis of primary sequence homology with other known Pseudomonas lipases, a number of putative active site residues located in conserved areas were found.
  • (10) Extensive sequence homologies and other genetic features are shared with the related oncogenic virus, human papillomavirus type 16, especially in the major reading frames.
  • (11) Since the plasmid-cured strains did not contain DNA sequences homologous to plasmid DNA, the gene for the free-inclusion protein must be encoded in the chromosome.
  • (12) Examination of the deduced amino acid sequence revealed an apparent homology to cAMP binding sites in several other proteins.
  • (13) Thus, introduction of arginine in position 5 with a hydrophobic amino acid in position 6 is compatible with high potency in several biological systems and results in compounds with lowered potency to release histamine compared to homologous peptides with tyrosine in position 5 and D-arginine in position 6.
  • (14) This receptor and a growing family of related cytokine receptors share homologous extracellular features, including a well-conserved WSXWS motif.
  • (15) Amino acid analysis indicated a significant number of serine amino acids: N-terminal sequence data demonstrated a high level of homology; and trypsin digestion followed by reversed-phase HPLC indicated the possibility of multiple phosphorylation sites.
  • (16) Homologous insemination in 52 couples during a period of one year yields a conception rate of 38.5%.
  • (17) The region is distinctive in that the sequence is absent from the homologous domain of the erythroid alpha chain and diverges from the normal internal repeat structure observed throughout other spectrins.
  • (18) Surrounding intact ipsilateral structures are more important for the recovery of some of the language functions, such as motor output and phonemic assembly, than homologous contralateral structures.
  • (19) The results show that in both viral DNAs cleavage occurs at the origin and at one additional site which shows striking sequence homology with the origin region.
  • (20) The most striking homology was to yeast SEC7 in the central domain of the gene (57% identical over 466 bp) and also the protein level (42% identical amino acids; 39% conserved amino acids).

Similarity


Definition:

  • (n.) The quality or state of being similar; likeness; resemblance; as, a similarity of features.

Example Sentences:

  • (1) Similar experimental manipulation has yielded in vitro lines established from avian B-cell lymphomas expressing elevated levels of c-myc or v-rel.
  • (2) The distribution and configuration of the experimental ruptures were similar to those usually noted as complications of human myocardial infarction.
  • (3) The antiarrhythmic activity similar to that of quinidine (with ca.
  • (4) It is concluded that during exposure to simulated microgravity early signs of osteoporosis occur in the tibial spongiosa and that changes in the spongy matter of tubular bones and vertebrae are similar and systemic.
  • (5) within 12 h of birth followed by similar injections every day for 10 consecutive days and then every second day for a further 8 weeks, with mycoplasma broth medium (tolerogen), to induce immune tolerance.
  • (6) Nutritionally rehabilitated animals had similar numbers of nucleoli to control rats.
  • (7) These studies led to the following conclusions: (a) all the prominent NHP which remain bound to DNA are also present in somewhat similar proportions in the saline-EDTA, Tris, and 0.35 M NaCl washes of nuclei; (b) a protein comigrating with actin is prominent in the first saline-EDTA wash of nuclei, but present as only a minor band in the subsequent washes and on washed chromatin; (c) the presence of nuclear matrix proteins in all the nuclear washes and cytosol indicates that these proteins are distributed throughout the cell; (d) a histone-binding protein (J2) analogous to the HMG1 protein of K. V. Shooter, G.H.
  • (8) As a consequence, similar response curves were obtained for urine specimens containing morphine or barbiturates.
  • (9) The 1989 results were compared with those of a similar survey performed in 1986.
  • (10) We similarly evaluated the ability of other phospholipids to form stable foam at various concentrations and ethanol volume fractions and found: bovine brain sphingomyelin greater than dipalmitoyl 3-sn-phosphatidylcholine greater than egg sphingomyelin greater than egg lecithin greater than phosphatidylglycerol.
  • (11) The prevalence of 24.4% among Mexican American men was similar to that among men from other ethnic backgrounds.
  • (12) Because cystine in medium was converted rapidly to cysteine and cysteinyl-NAC in the presence of NAC and given that cysteine has a higher affinity for uptake by EC than cystine, we conclude that the enhanced uptake of radioactivity was in the form of cysteine and at least part of the stimulatory effect of NAC on EC glutathione was due to a formation of cysteine by a mixed disulfide reaction of NAC with cystine similar to that previously reported for Chinese hamster ovarian cells (R. D. Issels et al.
  • (13) Microionophoretically applied excitatory amino acids induced firing of extracellularly recorded single units in a tissue slice preparation of the mouse cochlear nucleus, and the similarly applied antagonist 2-amino-5-phosphonovalerate (2APV) was demonstrated to be a selective N-methyl-D-aspartate (NMDA) receptor antagonist.
  • (14) Although Jeggo's Chinese hamster ovary cells were more responsive to mAMSA, novo still abrogated mAMSA toxicity in the mutant cells as well as in the parental Chinese hamster ovary cells 2,4-Dinitrophenol acted similarly to novo with respect to mAMSA killing, but neither compound reduced the ATP content of V79 cells.
  • (15) Methanosphaera stadtmanae reduces methanol to CH4 in a similar way as Methanosarcina barkeri.
  • (16) This study compared the non-invasive vascular profiles, coagulation tests, and rheological profiles of 46 consecutive cases of low-tension glaucoma with 69 similarly unselected cases of high-tension glaucoma and 47 age-matched controls.
  • (17) Similarly, doses of deferoxamine at the time of the study were not different.
  • (18) In the presence of insulin, a qualitatively similar pattern of increasing responses to albumin is observed; the enhancement of each response by insulin is, however, only slightly potentiated by higher albumin concentrations.
  • (19) The specific activities of extracts from cells grown under phototrophic and aerobic conditions were similar and not affected by the concentration of iron in the growth media.
  • (20) The thermoregulatory responses of this American marsupial were, in most aspects, similar to those of Australian marsupials.