Could two sperm from one male be identical?

Question

It seems to me that unlike snowflakes, there isn't an infinite number of possible variations of sperm from one male. Isn't there a finite number of genes and just two possibilities for each gene resulting in a limited number of variations? Given the total number of sperm produced over a lifetime isn't it likely that there would be some duplicates?

Answer 1

Actually what muddles the equation is the "crossing-over" of genes and mutation. In meiosis, the chromosomes exchange genes prior to the reduction division which leads to the independent assortment of genes in more ways than just two AND:

Each gene has a 1/10,000 chance of mutation with each division leading to nearly infinite assortment possibilities.

Surely, in all man kind one man has produced two genetically identical sperm but it would be a challenge to find out who it was and when.

Old Doc

Answer 2

it's imporbable but not impossible..

doesn't mean that the child will be the same.. you'd need two sperm and two eggs to be identical.. it'd be VERY cool if that ever happened

once in a million-trillion chance

Answer 3

There are to many variations to make is likely.  If it were just a matter of there being 2^23 (only about 8,000,000) ways to assort chromosomes, I would agree.  Unfortunately, there are crossing over events that increase the randomness, and replication itself is error prone.  All in all, I'd have to say that identical is next to impossible.

Answer 4

Sure, it's possible for two to be identical, but less likely than you may think. Even very simple mutations to the DNA would make them different.

Answer 5

I imagine most would get you to either one of two conclusions.

Answer 6

yea but the chances of having a child later that's exactly like an older  child of yours are very, very slim.

Unless of course you impregnate your wife every year....

but even then, you have to remember there is genetic variation from both parents.

I remember once reading in a text book, that by combining all the possible variations from random fertilization to random division...there are 6 billion possibilities between a couple.

Answer 7

yes it is possible, but unlikely.  If there were no crossing over during meiosis, there would be approximately 1/8388608 possible combinations of sperm.  Crossing over happens very often though, and because of this it is much less likely to happen.  Thus, over a lifetime there may be some duplicate sperm.

Answer 8

Yes you are correct.  It is possible ... but *extremely* unlikely.

The odds are about the same as taking a jar of 23 coins (representing 23 pairs of chromosomes), spilling them all on a table, and having them all come up tails.