T3M1 Flashcards
Genes are made up of
DNA
Genes contain the instructions to make
proteins
Genes can vary in size from
few hundred DNA nucleotide bases to thousands
Human genome project estimates humans have how many genes?
20,000- 25,000 genes that code for proteins (some coding for different versions of the same protein)
Housekeeping genes are constitutively expressed
‘ON’ all the time includes: structural proteins, ribosomal
proteins etc.
Regulated genes are expressed
only when needed (enzymes)
Fastest way to express a gene
post-translational regulation
Slowest way to express a gene
transcriptional control regulation
Most efficient way to express a gene
transcriptional regulation
Transcriptional Control
Ability of RNA polymerase to bind to or transcribe a gene
Translational Control
Translation rates, lifetime of RNA
Post-translational Control
Post-translational modifications which may change folding and/or activity
What is needed for prokaryotic growth?
favourable temperature, nutrient rich environment with amino acids and carbohydrates
The DNA of the bacterial nucleoid contains
the information that is required to orchestrate a
response to any change in the environment
Housekeeping genes
genes that are required all of the time for normal functions
Regulated genes
genes can be turned on and off on an as-needed basis
What type of gene is constitutively
expressed, and always being transcribed and translated?
housekeeping genes
Housekeeping gene examples
genes that are important for structural proteins of the cell, RNA and DNA polymerases and genes that are coding for ribosomal proteins
Housekeeping genes allow for
constant maintenance of general cellular activities
When exposed to a changing environment, bacterial cells can respond by
altering the expression pattern of some genes
Regulated bacterial genes can be transcribed and translated to allow for
the production of important enzymes
or proteins that are needed to bring about
changes in growth and division
Enzymes are required to
metabolize nutrients
Prefered energy source of E.coli
glucose
If we grow E. coli cells in an environment that
contains both glucose and the disaccharide
lactose
bacteria will still metabolize all the glucose before switching to utilizing lactose as a
fuel source
What activates the switch between glucose and lactose use?
products of glucose metabolism
Lactose is made up of
one molecule each of glucose and galactose
Enzyme that can metabolize lactose to produce glucose and galactose
B-galactosidase
B-galactosidase is produced by
turning on transcription of the B-galactosidase
gene when there is lactose available and no glucose available
In the 1960’s, Francois Jacob and Jacques Monod investigated
how E. coli are able to produce the B-galactosidase that is needed for lactose metabolism
Jacob and Monod observed that the production of the B-galactosidase enzyme is dependent upon
the presence of lactose in the environment
Jacob and Monod experiments
grew E. coli in a lactose-free medium, added lactose to the medium, and then removed it again. At the same time, they measured the amount of B- galactosidase enzyme produced in the cultured cells
Jacob and Monod found from their experiment
amount of B-galactosidase protein produced by the E. coli cells began to steadily increase in response to the addition of lactose to the growth media. They also saw that the production of the B-galactosidase ceased once the lactose was removed
Jacob and Monod results
lactose in the growth medium induced expression of the B-galactosidase gene
Further research from Jacob and Monod led to
an explanation of the mechanisms that control B-galactosidase gene expression
Who won Nobel Prize in Physiology or Medicine in 1965 for their work on the regulation of gene expression?
Jacob and Monod
The term gene expression means
functional product of the gene is made,
modified and activated
Protein coding genes
transcription, translation, and protein modification must be completed
Protein coding distinct levels of regulation
- transcriptional control
to allow for the transcription of DNA to mRNA - translational control to allow for the translation of mRNA to proteins
- post-translational control to allow for modifications and activation of produced proteins
The regulation of the expression of an activated protein must take into consideration
how each of these levels of control are modified
Transcriptional regulation controls
the amount of messenger RNA that is produced in the cell
Activation of transcription requires
proteins bind to a region near the beginning of the gene, the promoter, and increase the binding of the enzyme, RNA polymerase
By controlling the binding of proteins to the promoter, the cell can
activate or inhibit transcription
Initiation of translation in eukaryotes occurs by
the binding of the ribosome to the 5’ end or 5’CAP of the mRNA
Initiation of translation in prokaryotes
the ribosome will bind to and initiate
translation at the specific Shine-Dalgarno
sequences
The rate at which translation occurs will affect
the amount of protein that is produced
The amount of protein produced depends upon
the stability of the mRNA (If the mRNA is quickly degraded, then very little protein will be made)
What allows the polypeptide chain to be folded into a functional three-dimensional structure?
post-translational control mechanisms
Post-translational regulation allows the cell to
have a stockpile of protein in the cell that is simply inactive
In transcriptional regulation, expression of a functional protein requires that
the cell activate transcription, complete
translation, and finally modify the protein product
Transcriptional regulation is often prevalent with
more drastic environmental changes that a cell
can be exposed to
Why is transcriptional regulation most efficient?
the cell does not waste any energy or resources making a mRNA or polypeptide
