Gibberellin (16.2)

• Gibberellin plays a role in stem elongation
• Two alleles

  • Le (tall plants)
  • le (short plants)
• homozygous recessive individuals will be short
• le genes regulation the production of an enzyme that forms active gibberellin
• recessive le alleles result in a NON FUNCTIONAL ENZYME
• recessive alleles are only one nucleotide different from dominant.

  -

  Causes amino acid substitution Threonine - Alanine
• In homozygous recessive individuals for le gene- Threonine is substituted to alanine
• changes the primary structure of ACTIVE SITE making it non-functional
• non functional enzyme = no active gibberellin formed = short plants
• homozygous recessive individuals are dwarves
• farmers can apply active gibberellin to shorter plants to stimulate growth