Anyone ever read/heard anything about this or researched this?!
Question: My cousin just gave birth to the 4th set of identical twins in my family within two generations. I've heard that having identical twins isn't hereditary (sp?) but fraternal twins are. Anyone have any info on this?
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I believe identical twins and fraternal twins are both hereditary. It is quite common what your cousin has experienced.
Other Answers:
Researced on twins;
IDENTICAL TWINS
Results from the splitting of one fertilized egg after conception. The two babies are genetically identical; they begin life with the same hereditary endowment. Identical twins are always the same sex and have the same blood type. Identical twins in appearance are highly similar but not exactly alike.It is said that fraternal twinning is hereditary while identical twinning is due to chance.
It is said that fraternal twinning is hereditary while identical twinning is due to chance.
More often, older women, African American women, women with higher sexual activity (studies found that more twins are conceived during the first three months of marriage), taller women, and women with previous children have a higher incidence of twins. Research has also shown that women who just go off the pill, possibly because of hormone levels, have a high incidence of twins as well. Nigerian women have the highest twinning rate in the world, because of their diet containing yams which contain a hormone (HGC) that stimulates ovulation. It is thought that fraternal twinning can be hereditary through the mother's side of the family. But just because you have fraternal twins in your family history is not a predictor of whether you'll have them or not. Contrary to popular belief, they don't always skip a generation. Identical twinning is more a stroke of chance and luck than heredity, although there has been studies where identicals have seemed to run in certain families as well. With the advent of fertiltiy drugs and IVF, more and more women are having multiple births.
Twins occur once in 90 births in the United States. African Americans have the most twins and Asians the fewest. These statistics are altered when a woman takes drugs to stimulate ovulation. These artificially induced twins are usually fraternal.
Twinning increases with women over 30, family history of twins, having one set of twins already, and having given birth to more than one child.
In the United States, a third of twins are identical, one third boy/girl and one third same sex fraternal.PROOF OF TWIN TYPES:
Several types of tests can be run to determine what type of twins you have if you are not sure. Such tests are usually done only for medical reason as they are very expensive. You can also tell as they grow older, their features will be come more sharply defined.
Examination of blood group systems :
This involves comparing cotwins' similarity in red blood cell factors. When differences in any of the 18 blood groups are found, the twins are classified as fraternal. However, twins may have no detectable difference in blood groups, but may be fraternal. Therefore, comparison of heritable physical features such as eye color is necessary.
Physical resemblance questionnaires.
Physical resemblance questionnaires may be used for twin classification if blood-typing is not possible. These forms request information about twins' similarity in gentically influenced characteristics, such as hair color, eye color, height and weight. This method shows approximately 95 percent agreement with results from blood-typing analyses.
DNA Fingerprinting.
Techniques that can reveal the identity of individuals based upon unique characteristics in genetic material are extremely accurate. DNA is present in all cells of the human body. Genes, the hereditary units that are transmitted from parents to children are segments of DNA. Scientists can obtain DNA from blood samples as well as from buccal cells. Buccal cells may be obtained by scraping the inner cheek with special brushes and/or swabs. This is normally a much less expensive procedure than the analysis of blood samples.
Examination of the placenta and fetal membranes.
The placenta and fetal membranes provide less information on twin type than DNA testing. This is not a foolproof method of determining twin type.
Source(s):
http://www.geocities.com/wmotc/types.htm
as far as i know twins are heriditary period!
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