16.3.1 Gene control - Lac operon (part of inheritance) Flashcards
The nucleus of every cell in the human body contains the same ..?
genes
What is not expressed in every cell?
every gene
- Not all of these genes are expressed all the time
There are several mechanisms that exist within cells to make sure the correct genes are expressed in the correct cell at the right time.
What do they involve?
regulatory genes
What is a structural gene?
codes for a protein that has a function within a cell
For example, the F8 gene codes for the protein Factor VIII involved in blood clotting
What is a regulatory gene?
codes for a protein that helps to control the expression of another gene
Structural and regulatory genes that work together are usually found..?
close together
When are inducible enzymes only synthesized?
when their substrate is present
The presence of the substrate induces the synthesis of of the enzyme by causing the transcription of the gene for the enzyme to start
repressible enzymes synthesized as normal. Until?
repressor protein binds to an operator
The presence of the repressor protein represses the synthesis of the enzyme by causing the transcription of the gene for the enzyme to stop
Why can controlling synthesis of enzymes be beneficial for cells?
as it stops materials and energy being wasted
For example, using materials and energy to synthesize an enzyme when its substrate is not present and it can’t carry out its function would be highly wasteful
What do regulatory genes control?
- control structural genes and their levels of protein production
- sometimes have control over several structural genes at once
What do regulatory genes control?
- control structural genes and their levels of protein production
- sometimes have control over several structural genes at once
What can structural genes in prokaryotes form?
an operon
What is an operon?
a group or a cluster of genes that are controlled by the same promoter
Which operon is found in some bacteria which is the most well known?
lac operon
what does the lac operon control the production of?
the enzyme lactase (also called β-galactosidase) and two other structural proteins
What does lactase break down?
the substrate lactose so that it can be used as an energy source in the bacterial cell