Punnett Squares 1 As of 2015 the world population is 7244 b

Punnett Squares -

1. As of 2015, the world population is 7.244 billion and recent reports suggest humans have between 20,000 and 25,000 genes and at least 8% of these genes have multiple alleles. Based on the data you have collected using [http://scienceprimer.com/punnett-square-calculator], would you expect there to be individuals that have identical genotypes (outside of identical twins)? How about identical phenotypes, could there be someone in the world that is phenotypically identical to you? Please explain your answer.

Solution

Mendel’s law of independent assortment states that, during meiosis, each member of a pair of genes on homologous chromosomes tends to be randomly distributed into gametes independently of how other chromosomes are distributed. It results in giving all possible combinations in equal frequency.

The frequency of occurrence of allele combinations by independent assortment is calculated by the number of allele combinations to the power of number of pairs of chromosome. For example, in a human cell, 23 pairs of chromosomes would produce, 2²³ (8, 388608) combinations by independent assortment. Thus, except identical twins, no two individuals are completely genotypically identical.

In case of identical twins, their phenotypes are also different because the gene expression is partly regulated by the environment. However, we can observe phenotypic similarities in certain traits such as eye colour, skin colour, hair pattern, etc. Because of any two persons share the same allele type and dominance pattern, they are likely to exhibit the same phenotype though their genotypes are different. Also, any two individuals can exhibit two different phenotypes though they share the same genotype due to difference in penetrance/expressivity of the genes.