when the zygote divides into 2 (sometimes) it give rise to 2 daughter cells (zygote) which shuold have same sexes...cuz they arise from same genetic material... then do they still got 99.9% different DNA or are they clones?
yes or no give reasons.
2007-01-19 02:45:58 · 6 answers · asked by Anonymous in Science & Mathematics ➔ Biology
and how to differentiate among them?
2007-01-19 02:50:08 · update #1
Essentially yes, identical twins are clones. One twin begins his/her development with exactly the same DNA as the other twin. By definition, a clone is made by removing DNA from a woman's oocyte, and replacing it with the DNA from a cell of an organism that you want to clone. Then implanting this oocyte into a uterus. So by definition, a twin is not a clone, but just as clones have identical DNA, so do identical twins.
Now, there are clearly differences between twins, and not just psychological differences. There would also be similar differences between a person and his/her clone. How do we explain these? Simple . . . the environment, chance, and mutation.
Epigenetics refers to genetic mechanisms that do not involve a change in DNA, for example, certain genes are inactivated in cells on one copy of a chromosome, but active on the other allele. For many genes, this is a completely random prcoess, and depends on the environment, and chance. Sometimes the maternal copy of a gene is inactivated, but the paternal copy is kept active, and vice versa. The best example of this is formation of Barr bodies. Women have two X chromosomes, one they inherit from their mothers, and one they inherit from their fathers. Early in development, one of these X chromosomes is inactivated, and one is kept functional. This is a process that occurs by chance, and might differ between two female identical twins.
Of course life is not perfect, and DNA is replicated, and transcribed many many many times in many many many cells. Then proteins are made from RNA many many many times in many many many cells. These are not computer programs, but atoms dependent on the polarity created by electron and proton attractions and repulsions, as well as concentrations, and thus the process cannot be perfect every single time. So mutation also explains differences in phenotypes between twins and clones.
So in summary, yes twins and clones are essentially the same as far as their genomes and development are concerned. Both will develop almost as identical, but with slight variations due to the reasons I have given to you: chance, environment, and mutations.
2007-01-19 03:09:03 · answer #1 · answered by Brian B 4 · 0⤊ 1⤋
There is a good chance the DNA is identical but DNA replication is not perfect and anomalies occur:
1. Mutations-
a spontaneous genetic mutation can occur randomly at any time and may occur to only 1 twin altering the DNA
2. Crossing over
Chromosomes cross over at certain strategic points and the two twins may have chromosome that did not cross over at the same hot spot
3. Identical twins can develop over time non-identical DNA by the differing environmental influences throughout their lives affect which genes are switched on or off. This is called epigenetic modification.
4. "mirror twins" are relatively rare identical twins with opposite features, that is, one may be right-handed and the other left.
5. "Polar twins" are idwntical twins that are fertilized by different sperm
Finally, Very rarer
1. there can be identical but different sex twins if XXY chromosomes appear in the twins one may drop the X and one the Y
2. if the twins are birth in different placentas, it is proven they will have different IQs, while same placenta have the same
2007-01-19 03:03:33 · answer #2 · answered by Anonymous · 0⤊ 0⤋
It depends on your definition of "clone". Since neither is derived from the other, neither is "cloned" from the other. They are intially genetically identical, just like a clones would be.
So, I say NO, not clones, because of how they came to be, but nearly indistinguishable from clones after the fact.
2007-01-19 02:50:46 · answer #3 · answered by enginerd 6 · 1⤊ 1⤋
mono zygotic twins are gentically identical. if you were to do a DNA test on them, you wouldn't be able to tell the 2 apart.
technically, such twins are not clones as they aren't derived from each other.
2007-01-19 02:57:46 · answer #4 · answered by rfedrocks 3 · 0⤊ 1⤋
A clone is different to a twin. Clones are created by scientists. Twins are created naturally by mummies and daddies.
2007-01-19 02:50:30 · answer #5 · answered by ZZ9 3 · 0⤊ 1⤋
Technically, yes. There are clones. They are duplicates of one another.
2007-01-19 02:49:35 · answer #6 · answered by Blunt Honesty 7 · 0⤊ 1⤋