Each is produced by the successive replications of a synapsed diploid pair of chromosomes. The replicas do not separate, but instead remain attached to each other in their extended state, a process known as endoreduplication.

At the start of the process, each synapsed pair has a DNA content of 2C (where C represents the DNA content of the individual chromosome). This amount then doubles up to nine times, at its maximum giving a content of 1024C. The number of doublings is different in the various tissues of the D. melanogaster larva.

TLS Online TPP Program

#Id: 7134

#Unit 6. System Physiology – Plant

Brassinosteroids are synthesized from the plant sterol campesterol, which is similar in structure to cholesterol. Members of the cytochrome P450 monooxygenase (CYP) enzyme family that are associated with the ER catalyze most of the reactions in the brassinosteroid biosynthesis pathway.

Mevalonic acid serves as a precursor of the triterpenoid pathway and is condensed and transformed to 2,3-oxidosqualene which further undergoes modification to form major plant sterols like sitosterols and campesterols.

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#Id: 7135

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7136

#Unit 6. System Physiology – Plant

TLS Online TPP Program

#Id: 7137

#Unit 6. System Physiology – Plant

BR biosynthetic pathway is a triterpenoid pathway. ls.

TLS Online TPP Program

#Id: 7138

#Unit 6. System Physiology – Plant

They regulate multiple physiological functions including seed germination, cell elongation, cell division, senescence, vascular-differentiation, reproduction, root development, photomorphogenesis, and also respond to various biotic and abiotic stresses.

BR-deficient mutants exhibits extreme dwarfism, altered leaf morphology, abnormal vascular development, delayed flowering and senescence, and reduced male fertility.

TLS Online TPP Program

#Id: 7139

#Unit 6. System Physiology – Plant

Bioactive brassinosteroid levels are also modulated by a variety of inactivation or catabolic reactions, including epimerization, oxidation, hydroxylation, sulfonation, and conjugation to glucose or lipids.