USA Biology Olympiad (USABO) Practice Exam

Which gene mutation pattern can lead to increased flower petal development?

1. Mutation in Gene A

2. Mutation in Gene B

3. Mutation in Gene C

4. No mutation in any gene

The correct answer is: Mutation in Gene C

The correct answer pertains to a mutation in Gene C, which is associated with pathways that regulate flower development, particularly in the formation of petals. In many flowering plants, specific genes are responsible for the growth and morphology of floral structures. These genes can be part of larger regulatory networks that determine how floral organs develop and differentiate from one another. When a mutation occurs in Gene C, it can enhance or modify the expression of downstream targets involved in petal formation, leading to increased petal development. For example, if Gene C normally represses a pathway that limits petal size or number, a mutation could relieve this repression, resulting in more pronounced petal traits. This outcome is supported by research in various model organisms, such as Arabidopsis thaliana, where mutations in similar genes result in floral phenotypes that exhibit increased petal size or an altered number of petals. In contrast, mutations in Gene A or Gene B might not impact petal development as significantly or could influence other aspects of flower morphology, such as sepals or reproductive organs. Not having any mutations would generally result in the canonical form of the plant’s flower without enhancement in petal development. Thus, the specific influence of Gene C mutations directly correlates with increased flower