2.Induction and repression of gene expression:
Induction or repression: turned on/off by environmental events, Some gene products rise and decrease in response to molecular signals.
Key term
housekeeping genes:
Some gene products are required all the time, and their genes are expressed at constant level in all the cells of a species or organism.
example: expression of insulin
Ⅲ. The modes of gene expression:
1.Constitutive gene expression (housekeeping gene) :
*expressing in almost all cells *expressing in all life period *influenced less by the environmental changes *housekeeping gene is constitutively expressed *only influenced by promoter and RNA polymerase
*repressible genes: decreased by repressors the decrease in gene expression is called repression.
Example: the enzymes catalyzing tryptophan biosynthesis.
Many of the genes for enzymes that catalyze steps in central metabolic pathways.
constitutive gene expression:
Constant, unregulated expression of the genes. It is only regulated by promoter and RNA pol.
*inducible genes: increased by inducers the process of increasing expression of the gene is called
induction. example: The expression of genes encoding DNA repair enzymes
Chapter 18
Regulation of gene expression
Based on the National
planning textbook，8th
edition, 2013
Section 1
Basic conception and characters of gene expression
DNA → mRNA → Protein (or DNA → RNA)
Ⅱ. Specificity of gene expression:
*Temporal specificity (Stage specificity) Not all genes are expressed all the time. In the human genome only a fraction are expressed at any given time. example: alpha fetal protein, AFP
in liver cancer cells, AFP is activated
*Spatial specificity (cell or tissue specificity) for specific tissue, some gene products have functions,
presence in very large amounts. Other gene products are needed in much smaller amounts.
3. Coordinate gene expression
➢ The genes that associate functionally are regulated to express together.
➢ Example: genes for enzymes and transport proteins participating in the same metabolism pathway (such as the enzymes for glycolysis)
Hale Waihona Puke . Gene expression:
The process in which gene was transcribed into RNA
and translated into protein. Or the process in which the functional product was
produced. (including the transcription of rRNA and tRNA)
Ⅳ. multiple levels and complexity of gene expression regulation:
➢Gene activation ➢Initiation of transcription ➢Posttranscriptional processing ➢Translation ➢Posttranslational modification
① ②
③
Ⅴ. Regulation of gene expression is the bases of growth and development :