What are the five steps of genetic expression?

1. Transcription – conversion of DNA to RNA

2. Post-transcriptional modifications

3. RNA transport

4. Translation or protein synthesis

5. Protein folding

1Initiation. The DNA molecule unwinds and separates to form a small open complex. RNA polymerase binds to the promoter of the template strand.

2Elongation. RNA polymerase moves along the template strand, synthesising an mRNA molecule. In prokaryotes RNA polymerase is a holoenzyme consisting of a number of subunits, including a sigma factor (transcription factor) that recognises the promoter. In eukaryotes there are three RNA polymerases: I, II and III. The process includes a proofreading mechanism.

3Termination. In prokaryotes there are two ways in which transcription is terminated. In Rho-dependent termination, a protein factor called "Rho" is responsible for disrupting the complex involving the template strand, RNA polymerase and RNA molecule. In Rho-independent termination, a loop forms at the end of the RNA molecule, causing it to detach itself. Termination in eukaryotes is more complicated, involving the addition of additional adenine nucleotides at the 3' of the RNA transcript (a process referred to as polyadenylation).

4Processing. After transcription the RNA molecule is processed in a number of ways: introns are removed and the exons are spliced together to form a mature mRNA molecule consisting of a single protein-coding sequence. RNA synthesis involves the normal base pairing rules, but the base thymine is replaced with the base uracil.

g1

choices:

a. g2. b. g1. c. m

cell division has two checkpoints namely, g1

checkpoint and spindle assembly checkpoint. the checkpoint which determines if

division has properly occurred is the g1 checkpoint. at this point, is a damage

in the dna is detected or  the has not reach the optimum size, the cell is

stopped in g1 and is not allowed to proceed to further process.

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