Gene expression; totipotency cells

Gene expression; totipotency cells

1. When the information in a gene is used to make a functional polypeptide chain by transcription and translation, ene expression is said to have taken place. During the life of any particular cell, only a very small proportion of the cells genes are expressed; most of a cells DNA is not translated into polypetides and thereofre has no effect on the phontype of the organism

2. The zygote of a diploid, sexually reproducing organism has the potential to grow and develop by mitosis and cellular specialization into an adult organism. Cells that retain this potential to form all parts of a mature organism is called totipotent. During development, totipotent cells mature and become specialised. A specialised cell translates only the part of its DNA that are needed to carry out its specialised funstions. Most if the DNA is not used.

3. In specialised cells, DNA that is not needed becomes inactivated. However, in many plant speices, this inactivation is reversible and whole new individuals can be grown from differentiated, specialised somatic cells. The ability of differentiated cells to develop in vitro into whole plants showed that differentiation does not neccessary result in irreversible changes in the DNA

4. Plant tissue culture has the potential to grow hundreds or thousands of gentically indentical plants (clones) form a single source in a relatively smalPl amount of space, using few resources, and in relatively short term. Basically a piece of plant is placed in a strile nutrient meduim where it multiplies. Plant species vary in their response to tissue culture; some are easier to culture than others. For some species, attempts to propagate them by tissue culture have been unsuccessful

5. The composition of the gowth medium depends on what you are trying to produce