Diagram Of The Human Fertilization Process

A Billion Seeds Get Fertilized: The Promise of Libraries Across Africa

A few weeks ago I attended the Startingbloc Institute for Social Innovation in New York. Despite five long days of great speakers, the true stars of the institute were the other 108 candidates in attendance. Stumbling through one striking conversation after another, I came across a true diamond. Idris Bello is a social entrepreneur (prefers the term “Afropreneur” which he wears on his sleeve, going by the beautiful traditional African outfit he wore into a Lower East Side club for the Startingbloc launch party…) and a lead member of the team Libraries Across Africa , a new social enterprise which promises empowerment through access.

LAA, a non-profit and recently winner of the technology prize in the 2011 Dell Social Innovation Competition , is simple concept with complex ramifications. Taking advantage of (and spurring on) the coming explosion in African IT demand—of 1 billion Africans only 10% have internet access; African bandwidth is slated to grow 500% over the next decade from 5.8 Tbit/s to 29.5 Tbit/s—LAA is going to set up libraries that also serve as internet portals and community centers.

Is Africa ready? Like the infamously controversial One Laptop Per Child initiative with its allegedly overly-American and cost inefficient proposal to equip the poorest children in the world with a $100 laptop, one may ask whether Africans are ready for LAA. Put another way, do Africans enjoy the requisite cognitive surplus to benefit from libraries and widespread internet access?

Firstly, it is often overlooked by armchair social entrepreneurs that Africa is a huge place—the second largest continent by population and size with 61 territories—and contains a diverse set of priorities. One community’s bottleneck may be intensive healthcare, another’s may be infrastructure development, and many of them will be stable enough to benefit dramatically from communal internet access and third places . LAA must choose its initial locations wisely to ensure maximum impact and growing momentum to support the mission. The first library will be built in Moree, a small seaside town in Ghana.

Second is the inspiring story of Malawian William Kamkwamba. Unable to afford school and forced to drop out at age 14, Kamkwamba used his spare time educating himself at a local library.

Genesis of chromosome abnormalities – talk2vip

There are essentially three developmental stages at which chromosome abnormalities may arise; gametogenesis, fertilization and embryogenesis. The process of gameto- genesis in humans varies considerably between the two sexes. In males, each cell that enters meiosis produces four spermatozoa; the process is continuous, taking 64 days in all. Once past puberty, the male remains fertile into old age. In contrast, the human female is born with a complete set of oogonia – no more develop after birth. The initial stages of the first meiotic division take place early in fetal life but, after synapsis and recombination, each cell enters a period of arrest until after puberty. One egg then  matures  in  each  monthly  cycle. Ovulation  occurs  when  the  oocyte  is  at metaphase II of meiosis and completion of the second division occurs after fertilization. Although there are several million oogonia at the outset, most are lost before birth and only a few hundred ever mature. Once the egg store is depleted, the menopause begins and the woman becomes infertile.

Errors arising  during meiosis

The complexities of chromosome behaviour during the two meiotic divisions provide ample opportunity for errors to arise. Recombination between non-sister chromatids during  prophase I has two functions – to recombine the genetic material and to ensure that synapsis persists long enough to allow proper alignment of the bivalent (paired chromosomes) on the metaphase spindle. In addition, cohesion needs to be maintained  at the centromere of each homologous chromosome until the second anaphase, to prevent precocious separation of the two chromatids.

Molecular studies of the origin of trisomy using DNA markers are now available for over 1000 conceptions (Koehler et al., 1996). Generally, errors at meiosis I of oogenesis predominate but there are notable exceptions. Among males with 47,XXY chromosomes (Klinefelter syndrome), the origin is almost equally divided between parental sexes, whereas over 80% of 45,X females lack a paternal sex chromosome (Hassold et al., 1992). For the autosomes, a paternal origin is evident for a significant number of trisomies affecting the larger chromosomes, while for trisomy 18, maternal meiosis II  errors  predominate  (Hassold  et  al.,  1996; Hassold  and  Hunt,  2001; see Table 3.2). The molecular studies also provide data on genetic recombination

Table 3.

Human reproductive biology

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