eight-month-old sororal twins napping
dizygotic (dz) or fraternal twins (also referred non-identical twins , dissimilar twins , biovular twins , and, informally in case of females, sororal twins ) occur when 2 fertilized eggs implanted in uterus wall @ same time. when 2 eggs independently fertilized 2 different sperm cells, fraternal twins result. 2 eggs, or ova, form 2 zygotes, hence terms dizygotic , biovular. fraternal twins are, essentially, 2 ordinary siblings happen born @ same time, since arise 2 separate eggs fertilized 2 separate sperm, ordinary siblings.
this common type of twin.
dizygotic twins, other siblings, have extremely small chance of having same chromosome profile. if happen have same chromosome profile, have different genetic material on each chromosome, due chromosomal crossover during meiosis. other siblings, dizygotic twins may similar, particularly given same age. however, dizygotic twins may different each other.
studies show there genetic proclivity dizygotic twinning. however, mother has effect on chances of having such twins; there no known mechanism father cause release of more 1 ovum. dizygotic twinning ranges 6 per thousand births in japan (similar rate of monozygotic twins) 14 , more per thousand in african countries.
dizygotic twins more common older mothers, twinning rates doubling in mothers on age of 35. advent of technologies , techniques assist women in getting pregnant, rate of fraternals has increased markedly.
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