What to ask some definitions of terms in Gene Expression

Protein synthesis consist of 2 major step
1. Transcription
2. Translation
(DNA (step 1)-> mRNA (step 2)-> protein, this conversion is known as central dogma)

Transcription
A process of copying DNA sequence on a mRNA for protein synthesis.

Translation
A process of translating DNA sequence into polypeptide with the help of tRNA. Three nucleotides (= 1 codon) encode either a specific amino acid or nonsense signal for termination of translation.

Transcription factor
Factor assisting the transcription process. For example, for helping the RNA polymerase to locate the promotor of the DNA

Promoter
Specific DNA sequence for binding of the RNA polymerase (with the help of transcription factors) to initiate transcription ( Located upstream of the transcribed region of DNA)

Enhancer
Enhancer related to the regulation of gene expression. Enhancer is a DNA sequence located near the gene, it is site for binding of activator ( signal protein that bind with enhancer). Once binding with activator, expression of gene is increase. For example, in Lac operon, CAP-cAMP complex is activator for gene activating the Lac gene.

2008-05-19 01:39:52 補充：
Splicing
A process of modifing mRNA before translation take place. mRNA consist of coding region ( exon) and noncoding region (intron), ie coding region used to encode protein while noncoding region is not responsible for coding protein. Thus, intron have to be removed in a process called splicing.

2008-05-19 01:41:21 補充：
Alternative splicing
Splicing that occur in the mRNA in different way to produce different mRNA to produce different gene products.

2008-05-19 01:41:37 補充：
(That mean cutting at different region to produce different mRNA sequence, for example a mRNA "ABCDEFGHIJK", in alternative splicing, one may cut CDE or cut at FGH to produce different mRNA depending on which product the cells need. )
Splicing

2008-05-19 01:42:16 補充：
For RT-PCR, I guess it is used for synthesis cDNA library
For RT, it is a process used to produced DNA from a RNA which is a reversed process of transcription process. RT occur naturally in some virus which store genetic information as RNA.

2008-05-19 01:42:25 補充：
Articificial RT process is carried out when making a cDNA library. cDNA library is a collection of DNA sequence that will be transcribed into mRNA, it is produced by coping all mRNA from a specific type of cell.

2008-05-19 01:42:29 補充：
PCR is a lab technique used to copy and amplify desired DNA sequence for storage and other experimental need.

2008-05-19 01:45:24 補充：
sorry for so much supplementary notes as knowledge plus has word limit for answer, and the whole anwer is type by myself, hope it can help u =]
BTW, are u undergrad student? becoz the question is actually quite hard for secondary student

2008-05-19 14:02:53 補充：
For promoter, eukaryotic cells have a promoter sequence which is highly conserved called TATA box, while prokaryotic cells' one is named as pribnow box

thx for the help, but its a bit too rough, thx anyway

Transcription:
(When a gene is going to express itself, the helix DNA have to be uncoiled
first)
Then, that gene will be copied in the form of mRNA (and transported to the
ribosome which is located at the cytoplasm.) This process is known as
transcription.

Transcription Factors:
It is used to located the promoter of the DNA molecule.

Translation:
When the mRNA molecule is transported to the ribosome, the bases(AUCG)
will be translated into corresponding codes for the arrangement of amino acids
[usually 3 bases represent a code]

Promoter:
It is the location of a starter of a gene.

其他個D幫你唔到, 我未學到