CIE A Level Biology复习笔记16.2.7 The Role of Gibberellin in Stem Elongation

Category: A-level课程, 教材笔记, 福利干货 Date: 2022年8月11日上午11:07

In some plants species their height is partially controlled by their genes
The Le gene dictates the height of some plants
It has two alleles: Le and le
- The dominant allele Le produces tall plants when present
- The recessive allele le produces shorter plants when present (in a homozygous individual)
The gene regulates the production of an enzyme that is involved in a pathway that forms active gibberellin GA1
Active gibberellin is a hormone that helps plants grow by stimulating cell division and elongation in the stem
The recessive allele le results in non-functional enzyme
- It is only one nucleotide different to the dominant allele
- This causes a single amino acid substitution (threonine -> alanine) in the primary structure of the enzyme
- This change in primary structure occurs at the active site of the enzyme, making it non-functional
Without this enzyme no active gibberellin is formed and plants are unable to grow tall
Plants that are homozygous for the recessive allele le are dwarves
Some farmers apply active gibberellin to shorter plants to stimulate growth