Interesting Facts

Male DNA doesn’t kick in until day 3 of cell division…

“Surprising to many, the male genome (sperm DNA) is silent in the first 3 days of embryo development. The oocyte drives the development and cleavage of the early embryo. On Day 4, a critical switch occurs, and the male genome is turned on. At this time, the maternal and paternal genomes begin to work in concert to orchestrate the activities of the newly developing embryo.

It is at this time - Day 4 - when abnormalities in the paternal genome may begin to have what can be profoundly devastating effects on embryo development. Therefore, using sperm with abnormal DNA for ICSI may lead to normal fertilization and early embryo development yet be followed by embryo death expressed as a failure to implant (no chemical pregnancy) or early pregnancy loss (prior to an ultrasound-confirmed heartbeat.)“

from: ICSI and SCSA Sperm Diagnostics

http://www.inciid.org/newsletter/feb/scsa.html





Maternal RNA helps fertilized egg read DNA instructions

“From the moment of fertilisation, the embryo grows as the cells of the fertilised egg multiply. However, there is a problem. How can the DNA be read if the materials needed to read it have not yet been produced? The answer is that they are provided by the mother in the form of mRNA and proteins. The early stages of development are controlled directly by the mother's genotype for about the first three weeks, in humans, after which the embryo's DNA takes over.”

from: Conception and Development

http://www.gender.org.uk/about/04embryo/44_cncp.htm





Paternal DNA grows placenta and gestational sac, maternal DNA grows healthy embryo

“...These observations suggest that genes expressed by the paternal genome are directed towards the development of extraembryonic tissues essential to support the growth of the embryo, while the maternal genome appears to be geared towards expressing genes that contribute to proper embryo development. The opposing tendencies of the male and female genomes as well as the elucidation from mouse studies that Igf2 and Igf2r are imprinted genes with conflicting functions led to the development of the most widely recognized theory of imprinting, the ‘parental conflict’ hypothesis (Haig and Graham, 1991; Moore and Haig, 1991). This theory proposes that the paternal genome has evolved to express genes that favour the extensive use of maternal resources and lead to optimal fetal development and growth, thus ensuring transmission of the father’s genes to the next generation. On the other hand, genes expressed by the maternal genome serve to counteract the effort made by paternally expressed genes, and limit investments in embryo development and growth in favour of salvaging resources for future pregnancies.”

from: Potential significance of genomic imprinting defects for reproduction and assisted reproductive technology

http://www.humupd.oupjournals.org/cgi/content/full/10/1/3