CIE A Level Biology復習筆記16.2.7 The Role of Gibberellin in Stem Elongation
The Role of Gibberellin in Stem Elongation
- 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
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