المرجع الألكتروني للمعلوماتية
القرآن الكريم وعلومه
العقائد الإسلامية
الفقه وأصوله 
الرجال والحديث 
سيرة الرسول وآله 
علوم اللغة العربية 
الأدب العربي 
الأسرة والمجتمع 
الأخلاق والأدعية 
التاريخ 
الادارة والاقتصاد 
علم الفيزياء 
علم الكيمياء 
علم الأحياء 
الرياضيات 
الهندسة المدنية 
الزراعة 
الجغرافية 
القانون 
اللغة الأنكليزية 
الأخبار 
الإعلام 
مكتبة الصور 
أقلام بمختلف الألوان 
إضاءات
مفتاح
أجوبة الإستفتاءات الشرعية
وثائقيات
النبات
الحيوان
الأحياء المجهرية
علم الأمراض
التقانة الإحيائية
التقنية الحياتية النانوية
علم الأجنة
الأحياء الجزيئي
علم وظائف الأعضاء
المضادات الحيوية| Is the probability of having twins determined by genetics |
 1019
 05:48 مساءً
التاريخ: 20-10-2020 |
المؤلف : Genetics Home Reference 
الكتاب أو المصدر : Help Me Understand Genetics 
الجزء والصفحة : |
أقرأ أيضاً
التاريخ: 20-12-2019
1607
التاريخ: 9-12-2020
1176
التاريخ: 19-10-2020
1456
التاريخ: 13-12-2015
1741
|
Is the probability of having twins determined by genetics ?
The likelihood of conceiving twins is a complex trait. It is probably affected by multiple genetic and environmental factors, depending on the type of twins. The two types of twins are classified as monozygotic and dizygotic.
Monozygotic (MZ) twins, also called identical twins, occur when a single egg cell is fertilized by a single sperm cell. The resulting zygote splits into two very early in development, leading to the formation of two separate embryos. MZ twins occur in 3 to 4 per 1,000 births worldwide. Research suggests that most cases of MZ twinning are not caused by genetic factors. However, a few families with a larger-than-expected number of MZ twins have been reported, which indicates that genetics may play a role. It is possible that genes involved in sticking cells together (cell adhesion) may contribute to MZ twinning, although this hypothesis has not been confirmed. Most of the time, the cause of MZ twinning is unknown.
Dizygotic (DZ) twins, also called fraternal twins, occur when two egg cells are each fertilized by a different sperm cell in the same menstrual cycle. DZ twins are about twice as common as MZ twins, and they are much more likely to run in families. Compared with the general population, women with a mother or sister who have had DZ twins are about twice as likely to have DZ twins themselves.
DZ twinning is thought to be a result of hyperovulation, which is the release of more than one egg in a single menstrual cycle. To explain how DZ twinning can run in families, researchers have looked for genetic factors that increase the chance of hyperovulation. However, studies examining the contributions of specific genes have had mixed and conflicting results. Few specific genes in humans have been definitively linked with hyperovulation or an increased
probability of DZ twinning.
Other factors known to influence the chance of having DZ twins include the mother’s age, ethnic background, diet, body composition, and number of other children. Assisted reproductive technologies such as in vitro fertilization (IVF) are also associated with an increased frequency of DZ twins.
|
|
|
في ذي قار.. العتبة العباسيّة تقدم دعوة لجامعة العين للمشاركةِ في حفل التخرّج المركزي للطلبة
|
|
|
|
العتبة العباسية تقدم دعوة لجامعة المثنى لمشاركة طلبتها في حفل التخرج المركزي
|
|
|
|
جامعة بغداد تؤكد مشاركتها في الحفل المركزي الرابع لتخرج طلبة الجامعات العراقية
|
|
|
|
جامعة الكرخ للعلوم: مشاركة طلبتنا في حفل التخرّج المركزي مدعاة فخر لنا
|
