The Maternal Effect
The phenomenon was further studied in fruit flies (what else!) and was found to determine four fundamental features in development
It seems to be important for correct development for all animals, although there appears to be little in the literature, especially for humans.
"A protein known as heat-shock factor-1 (HSF1) is a major transactivator of stress-inducible genes in response to environmental changes, but it is also implicated in extra-embryonic development and female fertility in mice. . . . . mouse embryos whose mothers lack this protein are unable to develop properly beyond the zygotic stage, although oocytes were ovulated and fertilized normally." The females concerned were mated with so-called "wild-type" males whose genes would be expected to be dominant to defective genes in the mother. Since they did not prevent the problem with the female's zygotes, it indicated it was caused by a 'maternal effect' mutation. That is to say, "HSF1 from the mother [rather than the zygotes own DNA] normally controls early post-fertilization development."(1)
In another recent study,(2) a gene called Mater, dependent on the maternal genome, was shown to be essential for embryonic development beyond the two-cell stage. It was shown to to be a maternal gene, because females lacking it are sterile, while null males are fertile.
We have, however, found one human study,(3) to do with sickle cell anemia and beta thallassemia. The genes responsible are recessive, and those who have both copies (are homozygous) experience severe problems. However, being heterozygous for the genes confers resistance to malaria, thus in a malaria-rich environment one would expect heterozygosity to predominate among the adult population.
The study looked at babies born to couples where one partner was heterozygous, while the other was homozygous. The Mendelian ratio of heterozygotes born to heterozygous mothers with homozygous fathers was higher than the other way round. The suggestion was that the maternal effect favoured the transmission of the sickle cell and beta-thalassemia alleles.
Do not confuse this with mitochondrial DNA which we discuss next
Bland, J., (2003) About Gender: The Maternal Effect
Book graphics courtesy of Amazon.co.uk
Web page copyright 1998-2006 Derby TV/TS Group. Text copyright Jed Bland.
Last amended 27.12.03