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The human twin birth rate in the United States rose 76% from 1980 through 2009, from 9.4 to 16.7 twin sets (18.8 to 33.3 twins) per 1,000 births. [5] The Yoruba people have the highest rate of twinning in the world, at 45–50 twin sets (90–100 twins) per 1,000 live births, [6] [7] [8] possibly because of high consumption of a specific type of yam containing a natural phytoestrogen which may ...
Various types of chorionicity and amniosity (how the baby's sac looks) in monozygotic (identical) twins as a result of when the fertilized egg divides. Monochorionic twins are monozygotic (identical) twins that share the same placenta. If the placenta is shared by more than two twins (see multiple birth), these are monochorionic multiples.
The power of twin designs arises from the fact that twins may be either identical (monozygotic (MZ), i.e. developing from a single fertilized egg and therefore sharing all of their polymorphic alleles) or fraternal (dizygotic (DZ), i.e. developing from two fertilized eggs and therefore sharing on average 50% of their alleles, the same level of genetic similarity found in non-twin siblings).
Identical or monozygotic twins share their genes, while fraternal or dizygotic twins are only as genetically similar as any other sibling pair. When twins both share a trait, they are concordant for this trait; and when they differ they are discordant. If identical twins have a higher rate of concordance for a trait than fraternal twins, it ...
Twin studies is an observational test using monozygotic twins and dizygotic twins, preferably same sex. They are used to figure out the environmental influence on complex traits. Monozygotic twins in particular are estimated to share 100% of their DNA with each other so any phenotypic differences should be caused by environmental influences. [2]
Various types of chorionicity and amniosity (how the baby's sac looks) in monozygotic (one egg/identical) twins as a result of when the blastocyst or embryo splits Monoamniotic twins are identical or semi-identical twins that share the same amniotic sac within their mother's uterus . [ 1 ]
The words homozygous, heterozygous, and hemizygous are used to describe the genotype of a diploid organism at a single locus on the DNA. Homozygous describes a genotype consisting of two identical alleles at a given locus, heterozygous describes a genotype consisting of two different alleles at a locus, hemizygous describes a genotype consisting of only a single copy of a particular gene in an ...
Therapeutic cloning would involve cloning cells from a human for use in medicine and transplants. It is an active area of research, and is in medical practice over the world. Two common methods of therapeutic cloning that are being researched are somatic-cell nuclear transfer and (more recently) pluripotent stem cell induction.