Moºtenirea de anomalii genetice

 teo4teos, on 27th March 2011, 01:34, said:

Intoleranþa primarã e mult mai rãspânditã.


Pisica sau câinele de exemplu, consumã lapte de la alte mamifere; ca adult.

 teo4teos, on 27th March 2011, 01:34, said:

Faptul cã unii secretã lactazã ºi ca adulþi, se datoraezã unei mutaþii genetice, undeva pe cromozomul 2; evident se transmite ereditar.

http://www.foodnavig...erance-mutation
http://www.genes-4u....enes/g4_029.htm

 teo4teos, on 27th March 2011, 01:34, said:

Toleranþa e o anomalie, din moment ce majoritatea unei populaþii (luatã în total) nu suferã de aceastã boalã ºi o parte din populaþie suferã.

Edited by m3th0dman, 28 March 2011 - 23:33.

 m3th0dman, on 29th March 2011, 00:27, said:

Da, asa e, dar asta fiindca le dau oamenii. In mod normal, mamiferele nu consuma lapte ca adulti.
Si asa cum am mai spus, chiar si cei care au intoleranta suporta lactoza in anumite cantitati. la fel si alte mamifere omnivore, presupun.

Quote

Uite, nu iti raspund eu, ii las pe specialisti sa o faca:


Hum Genet. 2009 Jan;124(6):579-91. Epub 2008 Nov 26.
Lactose digestion and the evolutionary genetics of lactase persistence.

Ingram CJ, Mulcare CA, Itan Y, Thomas MG, Swallow DM.

Department of Genetics Evolution and Environment, University College London, London, UK.
Abstract

It has been known for some 40 years that lactase production persists into adult life in some people but not in others. However, the mechanism and evolutionary significance of this variation have proved more elusive, and continue to excite the interest of investigators from different disciplines. This genetically determined trait differs in frequency worldwide and is due to cis-acting polymorphism of regulation of lactase gene expression. A single nucleotide polymorphism located 13.9 kb upstream from the lactase gene (C-13910 > T) was proposed to be the cause, and the -13910*T allele, which is widespread in Europe was found to be located on a very extended haplotype of 500 kb or more. The long region of haplotype conservation reflects a recent origin, and this, together with high frequencies, is evidence of positive selection, but also means that -13910*T might be an associated marker, rather than being causal of lactase persistence itself. Doubt about function was increased when it was shown that the original SNP did not account for lactase persistence in most African populations. However, the recent discovery that there are several other SNPs associated with lactase persistence in close proximity (within 100 bp), and that they all reside in a piece of sequence that has enhancer function in vitro, does suggest that they may each be functional, and their occurrence on different haplotype backgrounds shows that several independent mutations led to lactase persistence. Here we provide access to a database of worldwide distributions of lactase persistence and of the C-13910*T allele, as well as reviewing lactase molecular and population genetics and the role of selection in determining present day distributions of the lactase persistence phenotype.

Scuze pentru engleza. daca nu iti convine citarea directa data viitoare pun un link, pentru mine e mai simplu, dar pentru discutie cred ca e mai edificator asa.

Cuvintele cheie sunt: polimorfism in reglarea exprimarii genei lactaza; mutatia 13910 e mai degraba un marker decat o cauza
Traducere: mutatiile, ca sunt mai multe posibilitati, sunt la nivelul mecanismului de reglare a exprimarii genei respective, nu la nivelul genei in sine

Quote

mai intai hotaraste-te ce consideri anomalie: toleranta sau intoleranta? ca folosesti cand una cand alta si nu mai stiu de fapt ce consideri anomalie: intoleranta originala a mamiferelor sau toleranta actuala a unei parti a speciei Homo.

Apoi, de toleranta la lactoza nu sufera nimeni, dimpotriva, e chiar fericit cel ce o are. neexistand suferinta asociata unei anumite trasaturi nu o poti numi boala. Boala e considerata intoleranta, pentru ca genereaza diaree, voma, flatulenta, dureri abdominale. Nu orice modificare genetica sau fenotipica inseamna defect genetic sau boala.