Question

Lets assume that a single gene controls head color, lets assume we will set up a jar that represents gametes produced by a heterozygous male. We will put 10 beads of one color in the jar and then 10 beads of another color. Lets say we put 10 beads of blue color and 10 beads of red color and we will say that blue is dominant over red.

Question: There are only three possible "gamete jars" that one diploid individual can make. all blue, all red, or half red half blue why are there no other possibilities for the jar such as 75% red and 25% White?

Answer 1

Let allele of the gene responsible for head colour are B for blue and b for red. A diploid individual can make only three types of jars of gametes. Because it either contains BB genotype or Bb genotype or bb genotype. In BB case diploid individual produce all blue gametes. In bb case diploid individual produces only red colour gametes. In Bb genotype half gametes are blue and half are red because Mendel law of segregation. According to which alleles of genes segregates independently of each other during the gamete formation. So 50 percent will be one allele and 50 percent other allele of gene.

75 percentage red and 25 percent white is not possible as there is no allele that give white colour.