Biology

One plate, many entries

• 42Amyloid-β 42

  The more pathogenic human amyloid-β peptide is forty-two amino acids long. Aβ42 is named for that length. It is not the more abundant 40-residue form.

• 2n = 6x = 42Bread wheat 42

  Bread wheat carries forty-two chromosomes. Three subgenomes, written BBAADD. Sakamura counted them in 1918. The formula is still the field’s own: 2n = 6x = 42.

• 2n = 6x = 42Common oat 42

  Common oat carries forty-two chromosomes. Three sets of seven pairs, written AACCDD. The field writes 2n = 6x = 42. Same integer as bread wheat. Different plant. Different genomes.

• 42Forty-two teeth

  An adult dog, in the normal formula, has forty-two permanent teeth. Twenty on top, twenty-two below. Puppies have twenty-eight. Missing teeth are variation or pathology, not a second standard.

• 2n = 42Mesoplodon · 2n = 42

  Mesoplodon is one of the few cetacean genera with diploid number 2n = 42. Árnason 1978 counted 2n = 42 in M. europaeus and M. carlhubbsi. Kurihara et al. 2017 counted 2n = 42 in M. stejnegeri and M. carlhubbsi. Most Cetacea remain 2n = 44.

• ~42 dNeural ~42 days

  Developmental biology holds many multi-week windows. An exactly 42-day milestone must be sourced per species and endpoint. Not one law of the neural tube.

• 2n = 42Nyssaceae · 2n = 42

  Oginuma and Tobe 2021 report 2n = 42 in Camptotheca, Davidia, and Diplopanax, after setting dubious historical counts aside. Sister genera sit at 2n = 44 (Nyssa) and 2n = 26 (Mastixia). They read 2n = 42 as six sets of seven: hexaploid, basic number x = 7.

• ⁴²KPotassium-42

  Potassium-42 (Z = 19, A = 42) is a β⁻ radioisotope that decays to stable ⁴²Ca. The MIRD monograph prints a half-life of about 12.36 h. NNDC prints 12.355 h. It was used as a tracer for potassium exchange.

• 2n = 42Rattus 2n = 42

  The laboratory rat keeps its genome in forty-two chromosomes. Twenty autosome pairs and XY. A named committee wrote that down in 1973. The black rat next door is commonly 2n = 38. Same family, different count.

• 42 daysRed-cell storage

  Packed red cells are often stored up to about 42 days under standard refrigeration. Jurisdiction and additive decide the licence. It is a protocol, not a law of blood.