Differentiation :
Differentiation Although all cells contain the same genetic information they are not all identical.
The differentiation of a cell is controlled by switching certain genes ON or OFF.
Different sets of genes are active in different types of cells. GENETIC CODE Unnecessary genes
OFF Cell specific genes
ON Essential Genes
ON
Gene Action in Bacteria :
Gene Action in Bacteria Bacteria (and all cells) manufacture some enzymes only when required, so that energy and resources are saved. The Bacteria E. Coli produces ß- galactosidase which breaks down lactose into glucose and galactose, but only in the presence of lactose (inducer molecule) Regulator Operator Structural Produces repressor molecule which switches off operator Switches on structural genes Codes for enzyme
Slide 4:
Repressor: a molecule which stops the operator from working by binding to it when inducer molecule is ABSENT
Operator: A DNA sequence which when bonded to the repressor switches off the structural gene
Structural: A gene which codes for the required enzyme.
Gene Action :
Gene Action Regulator gene is switched on Repressor molecule synthesised LACTOSE ABSENT LACTOSE PRESENT Repressor molecule binds to operator Operator gene is switched OFF Structural gene remains switched OFF Lactose binds with repressor molecule preventing it from binding to operator Operator gene is switched ON Structural gene is switched ON ß- galactosidase is produced.
Metabolic Pathways :
Metabolic Pathways As enzymes are proteins they are coded by genes.
Several genes will control a metabolic pathway because various enzymes will be needed to control each reaction. Phenylalanine Tyrosine intermediate melanin Gene 1 Gene 1 Normal Enzyme 1 functional Ph. is converted
in Ty. Individual
is normal Abnormal Enzyme 1 non- functional Ph. Is converted PKU sufferer
into toxic
compounds