Question

Mendel studied the inheritance patterns of 12 different pairs of characters of the pea plant. He could ascertain the independent assortment for only 7 of these 12 pairs of characters by repeated experiments. What can be deduced from this?

• A. The pea plant could have atleast seven pairs of chromosomes.
• B. The pea plant can have a maximum of seven pairs of chromosomes.
• C. The pea plant has exactly seven pairs of chromosomes.
• D. The pea plant can have haploid chromosome number between 7 and 12 only.

Answer 1

Answer: (A)

The pea plant could have atleast seven pairs of chromosomes.

• Mendel's second law, the law of independent assortment, says that alleles of different genes assort independently of one another during gamete formation. The second law describes the outcome of dihybrid (two characters) crosses, or hybrid crosses involving more than two traits.
• A dihybrid is an individual that is a double heterozygote. The random alignment of homologous pairs of chromosomes along the metaphase 1 plate accounts for the law of independent assortment.
• This model works for genes that are on separate (non-homologous) chromosomes, but not necessarily for genes that are on the same chromosome. When Mendel studied these characters together, he found that all the seven characters chosen were controlled by seven pairs of alleles and they were located on seven different pairs of homologous chromosomes. If any two different pairs of alleles were to present on the same pair of chromosomes his conclusion would have been different.
• Hence, it can be deduced that the pea plant could have at least seven pairs of chromosomes.