Question

1) The hormone gibberellin is used during plant tissue culture in order to promote the elongation of stems along with other important developmental responses. Explain how this hormones can be used and in what stage of the tissue culture?

2)  Identify the main role of transcription factors in the protein synthesis process.

Answer 1

1. Answer:

Physiologically gibberellins can promote flowering, cone initiation in some conifers, germination of seeds, stem bolting and elongation by increasing cell division

In tissue culture, Gibberellins are mainly used to induce plantlet formation from adventive embryos formed in the culture. They are added to tissue culture media, to prevent the formation of roots, shoots, or somatic embryos. Some of the gibberellins are necessary for normal callus growth, they reduce the availability of endogenous auxin. Growth of shoots in meristem and shoot cultures may be enhanced by addition of Gibberellins to the culture media.

They are added at the initial stages of tissue culture for their positive effects and added at the end when negative effects are intended.

2. Answer:

Transcription factors:

The events in the initiation of transcription in eukaryotes, has three main stages:

i. Chromatin containing the promoter sequence made accessible to the transcription cascade

ii. Binding of transcription factors (TFs) to DNA sequences in the promoter region

iii, Stimulation of transcription by enhancers

A large number of transcription factors interact with eukaryotic promoter regions. In human about six Transcription factors are identified viz., TFIID, TFIIA, TFIIB, TFIF, TFIIE, TFIIH. Transcription factors bind to each other. These then bind to RNA polymerase enzyme

Transcription factors along with enhancers form activators that increases the gene expression by about 100 times. The loop in the chromatin accomodates the promoter and enhancer together making the transcription faster