Genetics 14
HC 11
14.1
The extent to which genes are expressed can vary under certain conditions, we speak of
gene regulation. There are also unregulated/constitutive genes:
- Constantly expressed
- Code for proteins continuously necessary for the survival conversely, gene
regulations focusses on what proteins are expressed where, when and how
much.
The benefit of gene regulation is that encoded proteins/RNA is only produced when
required, there is no waste of energy. If you get the nutrients form outside, why waste
energy into creating enzymes that generate those nutrients? Evolutionary speaking, an
organism can thus compete as efficiently as possible. Moreover, it enables adaptability.
Hence, gene regulation is important for:
- Metabolism: some enzymes that catalyse/metabolise the breakdown of sugars
are only required in an environment with a lot of sugar.
- Response to environmental stress: some proteins defend a bacterium against
intense stress, so they are only required during stressful situations.
- Cell division: only upon division are various specific proteins needed.
- Differentiation and development: only during embryonic growth are several
proteins needed, when they appear afterwards the cells are often cancerous.
The regulation of genes can happen at any point in the gene expression sequence, during
either transcription (regulate rate and termination) or translation (prevent ribosome from
translating RNA) or posttranslation (feedback inhibition or covalent modification of protein
structure.
In bacteria, the most common way to regulate gene expression is by increasing or
decreasing the rate of RNA synthesis during transcription. For this, there are regulatory
proteins in place that bind (in)directly to the DNA and have a consequence:
- Repressors: inhibit transcription negative control
- Activators: increase transcription rate positive control
- Small effector molecules: affect transcription regulation by binding to the
previously described regulatory proteins, whereby they cause a conformational
change in said proteins that affect whether or not they can bind to the DNA. Such
proteins thus have two binding sites, one where it binds to DNA and one where
effector molecules can bind to.
o Inducers: increase transcription by either binding to repressor and
inhibiting its binding to DNA or by binding to activator and causing it to
bind to DNA. Some genes may thus be regulated by inducers, called
inducible genes; transcription happens when there is an inducer.
o Corepressors: decrease transcription by binding to repressors causing it
to bind to DNA and actively suppress transcription
o Inhibitors: decrease transcription by binding to activators and prevent
them to bind to DNA and activate/increase transcription.
Genes that are regulated by corepressors and inhibitors are
repressible genes; transcription is stopped only via a repressor.
HC 11
14.1
The extent to which genes are expressed can vary under certain conditions, we speak of
gene regulation. There are also unregulated/constitutive genes:
- Constantly expressed
- Code for proteins continuously necessary for the survival conversely, gene
regulations focusses on what proteins are expressed where, when and how
much.
The benefit of gene regulation is that encoded proteins/RNA is only produced when
required, there is no waste of energy. If you get the nutrients form outside, why waste
energy into creating enzymes that generate those nutrients? Evolutionary speaking, an
organism can thus compete as efficiently as possible. Moreover, it enables adaptability.
Hence, gene regulation is important for:
- Metabolism: some enzymes that catalyse/metabolise the breakdown of sugars
are only required in an environment with a lot of sugar.
- Response to environmental stress: some proteins defend a bacterium against
intense stress, so they are only required during stressful situations.
- Cell division: only upon division are various specific proteins needed.
- Differentiation and development: only during embryonic growth are several
proteins needed, when they appear afterwards the cells are often cancerous.
The regulation of genes can happen at any point in the gene expression sequence, during
either transcription (regulate rate and termination) or translation (prevent ribosome from
translating RNA) or posttranslation (feedback inhibition or covalent modification of protein
structure.
In bacteria, the most common way to regulate gene expression is by increasing or
decreasing the rate of RNA synthesis during transcription. For this, there are regulatory
proteins in place that bind (in)directly to the DNA and have a consequence:
- Repressors: inhibit transcription negative control
- Activators: increase transcription rate positive control
- Small effector molecules: affect transcription regulation by binding to the
previously described regulatory proteins, whereby they cause a conformational
change in said proteins that affect whether or not they can bind to the DNA. Such
proteins thus have two binding sites, one where it binds to DNA and one where
effector molecules can bind to.
o Inducers: increase transcription by either binding to repressor and
inhibiting its binding to DNA or by binding to activator and causing it to
bind to DNA. Some genes may thus be regulated by inducers, called
inducible genes; transcription happens when there is an inducer.
o Corepressors: decrease transcription by binding to repressors causing it
to bind to DNA and actively suppress transcription
o Inhibitors: decrease transcription by binding to activators and prevent
them to bind to DNA and activate/increase transcription.
Genes that are regulated by corepressors and inhibitors are
repressible genes; transcription is stopped only via a repressor.
