Identical twins, Biology

Identical Twins

Human twins may be similar, when they are formed from one egg (monozygotic) or fraternal while they are the result of fertilization of two different ova released at the same time and fertilized through different sperms (dizygotic): From an embryological point of view identical twins are of greater interest. 0.25% of all births might be monozygotic twins. Current evidence indicates that twinning takes place at the blastocyst stage by the splitting of the inner cells mass. The cells of the ICM are refer totipotent i.e. they have the potential of forming a single dual or even a multiple embryonic disc. If by chance, the separation of inner cell mass takes place before day 5, even before the formation of trophoblast, which occurs in 33 percent of similar twins, then they have two separate chorion and amniotic cavities. (Figure (a)).

312_Identical Twins.png

Identical twins which share a common chorion, but two separate amniotic cavities indicate that the split in ICM came among the formation of chorion on day 5 and formation of amnion on day 9 as displayed in Fig.(b). This is the case in two thirds of identical twins. A small percentage of identical twins are born in a single chorion sharing single amniotic cavity as shown in Fig (c). This points out that the division occurred after day 9 after the implantation of the blastocyst. As seen in Fig (d), the embryonic disc may divide not completely i.e., the two new embryonic axes fail to separate completely and the outcome is conjoined twins. The degree of union may be little or quite extensive and the twins may be joined at any part of their body. It should be kept in mind, however, that conjoined twins represent an aberration in development that would usually lead to formation of identical twins. Most conjoined twins do not survive after birth but nowadays it is possible to separate some of them surgically and then one or both may survive to lead fairly normal lives.

Posted Date: 2/1/2013 4:42:20 AM | Location : United States







Related Discussions:- Identical twins, Assignment Help, Ask Question on Identical twins, Get Answer, Expert's Help, Identical twins Discussions

Write discussion on Identical twins
Your posts are moderated
Related Questions
Algae have cell wall made up of: 1. Cellulose, galactans and mannans 2. Hemicellulose, pectins and proteins 3. Pectins, cellulose and proteins 4. Cellulose, hemicellulo

Define Absorption, Storage and Elimination of Vitamin D? As we have already mentioned earlier, all fat-soluble vitamins share a common metabolic fate. Vitamin D is absorbed al

Explain the Properties Locust bean gum Locust bean gum is slightly soluble in room temperature water and must be heated to 75 to 85 o C for complete hydration and viscosity dev

Guidelines for diagnosis and treatment planning The diagnosis and planning the case is by far the most important step in the entire sequence of the treatment and due considerat

1. Write general characters of phylum mollusca and classify it upto classes, giving at least two examples of each class.

If you create an F2 generation by mating two of the F1 offspring from your cross of a pure-bred brown pig with a pure-bred heavy spotted red pig. Explain why the pigs in your F2 ge

Medical Nutrition Therapy Medical Nutrition Therapy  (MNT) is defined as  the  assessment of  the  nutritional status of  a client  followed  by  nutrition  therapy ranging Pon

Q. Define a closed circulatory system? A closed circulatory system is one in which blood circulates only inside blood vessels for this reason the blood pressure is higher in so

Q. To what substance is the acidic flavor of fermented milk due? Some bacteria ferment milk lactose by lactic fermentation producing lactic acid this product is responsible for

Systemic embolization occurs in 22 per cent to 50 per cent of cases of IE. Emboli often involve major arterial beds, including lungs, coronary arteries, spleen, bowel, and extremit