Hector was doing some experiments with plants. The plants have two variations of the flower color - pink or white. He used pollen from one plant and fertilized another plant. He noticed that sometimes when he crossed two plants with pink flowers, some offspring had white flowers. Explain how this could happen.

It happened as a result of Segregation in the heterozygous pink-flowered plants.

Explanation:

Gregor Mendel confirmed that organisms possess two forms of a gene called ALLELE. He, however, discovered in his LAW of DOMINANCE that one allele is capable of masking the expression of another allele in the same gene. The allele that masks is called DOMINANT allele while the allele being masked is called RECESSIVE allele.

Based on this concept, the genotype of an organism can either be homozygous (containing the same alleles) or heterozygous (containing different alleles). The homozygous can either contain two dominant alleles (phenotypically dominant) or two recessive alleles (phenotypically recessive). The heterozygous contains one dominant and one recessive allele, however, the dominant allele will cover up the expression of the recessive allele in this state. Hence, the dominant allele will be expressed.

This is the case of the two pink flowers that were crossed. They are both heterozygous i.e. contain one dominant (pink) and one recessive (white) allele. When these two plants are crossed, each allele will separate into gametes according to Mendel's law of SEGREGATION. Hence, when these gametes meet or combine, there is a 25% chance that two recessive alleles (white) will combine to produce a recessive offspring (white flower).