2007-05-21 01:39:48 · 8 answers · asked by Anonymous in Science & Mathematics ➔ Biology
Not entirely true: identical twins share the same base DNA.
In general, people have different DNA because DNA mutates, and because one inherits 23 chromosome from the mother and 23 from the father. If the mother and father had totally dissimilar chromosomes, then you'd have 4^23 possible variations for an offspring, that is 7E13 possibilities. The current earth population is merely 7E9, and the estimate of the total number of humans that ever existed is 1E11.
And that is assuming that any given chromosome exists in only 4 variations (that works to 3 X and one Y) which is not the case, and that chromosomes did not mutate.
2007-05-21 01:47:34 · answer #1 · answered by Vincent G 7 · 0⤊ 0⤋
Each person receives half of their genes from each parent but the mix is different except for identical twins. DNA is formed like a set of helical ladders and each ladder divides in two. Each parent provides half of a whole ladder in a fertilized egg but the ladder halves do not match exactly because each parent is unique. Therefore the ladder halves must find a unique way each time to make a whole ladder that forms a unique offspring. When the baby's DNA splits to form new cells a half ladder goes into each new cell and is made complete by a soup of 'spare parts.' and each new cell obtains a complete new identical set of ladders.
2007-05-21 01:49:11 · answer #2 · answered by Kes 7 · 0⤊ 0⤋
You answered your own question: genes. Genes have the capacity to be nearly infinitely variable so no two people are alike. Even identical twins have a few different gene sequences. Our genes mutate and we pass them along to the next generation and so forth and so on.
2007-05-21 01:43:13 · answer #3 · answered by Lady Geologist 7 · 0⤊ 0⤋
Because we reproduce sexually and thus have 2 possibilities for each trait expressed in our offspring. Asexual reproduction results in identical offspring.
Aren't we lucky?
2007-05-21 01:48:05 · answer #4 · answered by chemmie 4 · 0⤊ 0⤋
during meiosis,pachytene stage non sister chromatids (paternal&maternal)exchange their parts i.e only small regions-this leads to genetic variations,the sister chromatids remain same.Brothers&
sisters of same family might contain same genes in sister chromatids
2007-05-21 01:51:34 · answer #5 · answered by abc 1 · 0⤊ 0⤋
To increase the chances of the species to survive.
2007-05-21 01:42:48 · answer #6 · answered by Totally Blunt 7 · 0⤊ 0⤋
Diversity is strength. If we were all the same, one disease would wipe us out.
2007-05-21 01:45:01 · answer #7 · answered by Anonymous · 0⤊ 0⤋
God made us that way.
2007-05-21 01:52:42 · answer #8 · answered by Simple Life? HAHA 3 · 0⤊ 0⤋
DNA.. duh!
2007-05-21 01:43:05 · answer #9 · answered by Anonymous · 0⤊ 0⤋