Final answer:
The probability of two gametes uniting to form a zygote during random mating is determined by the laws of probability and can be illustrated using tools like Punnett squares. It mirrors the 50/50 chance seen in coin tosses, with the likelihood of inheritance of alleles being equal under the law of segregation and the law of independent assortment.
Step-by-step explanation:
The probability that two gametes (alleles) unite to form a zygote (diploid genotype) during random mating is best understood through the laws of probability, much like the probabilities associated with tossing a coin. When gametes are produced by an organism with a heterozygous genotype, such as Bb, each gamete has a 50 percent chance of receiving either the dominant B allele or the recessive b allele. Similarly, in the case of a combination of these gametes from different parents, the law of segregation and the law of independent assortment dictate equality in the probability of gamete combination. For example, in the F2 generation after a cross between a homozygous dominant (AA) and a homozygous recessive (aa), the probability of forming a heterozygous genotype (Aa) is 100 percent, since all gametes from the dominant parent carry the A allele and all from the recessive parent carry the allele.
Moreover, the formation of various genotype combinations in the offspring can be represented using a Punnett square. For a self-cross of a heterozygous YyRr, there would be four equally likely gametes (YR, Yr, yR, and yr), resulting in 16 equally likely genotypic combinations, which infer a phenotypic ratio that can be predicted using probability.