Humans (and many other organisms) have more than 7 pairs of chromosomes and have thousands of different traits. Explain why it is so unlikely for two individuals to have the same genotype.. thanks!!!
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Let's keep it simple by just comparing siblings who have the same parents (no half sibs). So both sibs get all their chromosomes, hence all their alleles from the same two parents. When meiosis takes place to create eggs and sperm, the two sets of chromosomes in each parent have to separate so that egg and sperm each have half the number of chromosomes so that at fertilization, the new offspring has the normal set.
So during meiosis, one of each pairs of chromosomes separate to take the cell from diploid to haploid. For each pair it is random which goes to each daughter cell. Humans have 23 pairs of chromosomes so there are 2^23 different ways to separate the chromosomes. So the chances of having two sperm get the same sets of chromosomes is 1 in 2^23, a very small number. So two siblings with the same parents already have a very, very small chance of having the same genotype. For two unrelated individuals, the chances are even lower.
So during meiosis, one of each pairs of chromosomes separate to take the cell from diploid to haploid. For each pair it is random which goes to each daughter cell. Humans have 23 pairs of chromosomes so there are 2^23 different ways to separate the chromosomes. So the chances of having two sperm get the same sets of chromosomes is 1 in 2^23, a very small number. So two siblings with the same parents already have a very, very small chance of having the same genotype. For two unrelated individuals, the chances are even lower.