Explain how the breakdown of lactose is regulated at the gene level.
Eg, The Lac Operon in E.coli -
Without lactose in the cell, the repressor protein binds to the operator and prevents the read through of RNA polymerase into the three structural genes. With lactose in the cell, lactose binds to the repressor. This causes a structural change in the repressor and it loses its affinity for the operator. Thus RNA polymerase can then bind to the promoter and transcribe the structural genes. In this system lactose acts as an effector molecule.
Explain how the lac operon operates differently from the trp operon.
very differently. they are both sweet mechanisms.
lac operon.
this is controlled by both activation and inhibition. if there is glucose in the cell then the activator is inhibited. when there is high levels of AMP compared to ATP the inhibitor is inhibited. therefore only in the absence of glucose (the major source of energy) and ATP will the cell use lactose instead.
trp operon.
this one has a length of mRNA that controls the translation of the proteins. there are 3 sections that can form a hairpin structure on this initial sequence. there is 3 codons at the start that code for tryptophan. this means that 3 tryptophan have to be near by to be used. if these 3 are around then the ribosome goes quickly through it and the hairpin structures that can form make a termination sequence. this stops the translation of the mRNA. if there is no tryptophan around the ribosome is stalled and therefore other hairpin structures are formed stopping the termination sequence from being formed. this therefore means the ribosome can make the proteins that are needed for the production of tryptophan
How is a promoter region different than an operator region?
A promoter is a region of DNA that facilitates the transcription of a particular gene. Promoters are typically located near the genes they regulate, on the same strand and upstream (towards the 5' region of the sense strand).
Group of genes that are found next to each other on a chromosome, and are turned on and off as an integrated unit. They usually produce enzymes that control different steps in the same biochemical pathway by a single operator gene or operator sequence.
Explain how gene regulation is different in eukaryotic cells and prokaryotic cells.
There are several mechanisms you can use to explain HOW gene regulation is more complex in eukaryotes than prokaryotes, but the question asks WHY it is more complex.
The reason is because eukaryotes have many types of specialized cells that have to express different genes at different times. The human body alone has something like 200 different cell types--each performing a different function. This function is dictated by what genes are being expressed.
Second, eukaryotes tend to be much larger than prokaryotes. Stimuli sensed at one part of a eukaryotic body must be relayed to other cells in order for the organism to respond properly (homeostasis). This entails the need for more complex regulatory mechanisms involving hormones and other signaling molecules that must travel long distances quickly.
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