What is Zygotic - born on the same day to One mother but not Twins

Zygosity refers to the similarity of genes for a trait (inherited characteristic) in an organism. If both genes are the same, the organism is homozygous for the trait. If both genes are different, the organism is heterozygous for that trait. If one gene is missing, it is hemizygous, and if both genes are missing, it is nullizygous.

Sure not the simplest of things to understand but one feels that this was heard somewhere and somewhat comprehensible !  -  the impact of cinema is so strong….. the box office buster Enthiran [Robot] directed by Shankar was a science fiction.  The film featured Rajinikanth in dual roles as a scientist and an android robot.  The robot named chitti possessed magical power which included reading the contents of any book by virtually scanning it in a few seconds.  In one of the scenes, Aishwarya Rai would be preparing for her examination in Medical science and Chitti would revise the minutest details astonishingly.  -  that was about monozygotic twins.  There have been innumerable tales of ‘twins’ in Indian cinema – people getting confused and mistaking 0ne for the other is the commonest of the themes. 

Identical or monozygotic (MZ) twins occur when a single egg is fertilized to form one zygote (hence, "monozygotic") which then divides into two separate embryos.  There are an estimated 11 million sets of identical twins and triplets in the world today.  A twin is one of two offspring produced in the same pregnancy.

Scientifically, it is possible that two singletons to be identical if all 23 chromosomes in both gametes from the mother and father were to be exact matches from one birth to the next.

Today read about a story of a woman giving birth to two babies on the same day but they ARE NOT TWINS !!!!

 photo from dailymail.co.uk

This is an real life incident of Julia Grovenburg and her husband Todd that occurred in UK and reported in http://www.dailymail.co.uk/.    Julia reportedly even considered adopting a baby from a foreign country in order to complete their dreams of having a family.  Luckily, in July 2009, Julia's pregnancy test finally came back positive.  Strangely, she actually became pregnant twice within two weeks, shocking the world with their unusual pregnancy news.  As one of only 11 women ever reported to get pregnant while already pregnant, Mrs Grovenburg's pregnancy was eventually identified as 'superfetation', meaning two babies are conceived at different times, born on the same day yet - medically speaking - are not considered twins.  Mrs Grovenburg gave birth by Caesarean section to two healthy non-twin babies, Jillian and Hudson, on December 2, 2010 – it was not all that simple.

The newspaper mentions that according to the rhythm of the heartbeats and the visual displayed on the ultrasound, both babies had gestational ages about two-and-a-half weeks apart from one another. And worse yet, their due dates were so far apart that that if Julia went into labour early she could risk losing one or both of her babies.  Given the babies' two-and-a-half-week age gap, Mrs Grovenburg's due dates were December 24, 2009 and January 14, 2010.  But with doctors still unsure if she' be delivering one or both babies at a time, the main concern was to get as close to full term as possible.  After a very stressful yet normal pregnancy, Mrs Grovenburg gave birth by Caesarean section to two healthy babies, Jillian and Hudson, on December 2, 2010.

Superfetation, scientifically is the simultaneous occurrence of more than one stage of developing embryo in the same mother. In mammals it manifests as the formation of a fetus from a different menstrual cycle while another embryo is already present in the uterus. Superfetation is claimed to be common in some species of animals, but is extremely rare in humans.

Incredible but strange things do happen…………

Regards – S. Sampathkumar.