D2.2 Genetic Expression Flashcards
What is gene expression?
The mechanism by which information in genes has effects on the phenotype
Includes stages like transcription, translation, and function of protein products.
What are the common stages in gene expression?
Transcription, translation, and the function of a protein product
Such as an enzyme.
What is the role of transcription factors in gene expression?
bind to specific regulatory sequences in DNA and control the rate of transcription.
How does mRNA degradation regulate translation?
Control of the lifespan of mRNA, before being broken down by nucleases.
What is epigenesis?
The development of patterns of differentiation in the cells of a multicellular organism without altering DNA base sequences
Alters phenotype but not genotype.
What are epigenetic tags?
molecular markers or modifications in nucleosomes that can regulate gene expression.
What is the consequence of methylation of cytosine in DNA?
Represses transcription and therefore expression of the downstream gene.
What is epigenetic inheritance?
Heritable changes to gene expression passed on to daughter cells or offspring without changes in nucleotide sequence.
What environmental factors can affect gene expression?
- air pollution => oxidative stress
- diet => folic acid = more methylation
- temperature => reptiles
What is the operon model in bacterial gene regulation?
A model where an operator, promoter, and structural genes regulate transcription.
What is the function of a promoter?
A DNA sequence that acts as a binding site for RNA polymerase.
What distinguishes a repressible operon from an inducible operon?
Repressible operons are usually on but can be inhibited, while inducible operons are usually off but can be turned on.
What happens in the trp operon when tryptophan is present?
Tryptophan binds to the repressor, causing it to change shape and bind to the promoter, inhibiting gene expression.
What is the role of lactose in the lac operon?
Lactose binds to the repressor, causing it to change shape and allowing RNA polymerase to bind to the promoter.
What is the phenotype of a cell or organism?
Observable characteristics determined by the combination of genes expressed and their expression levels.
How do cell types differ in an organism?
They express different sets of genes, leading to distinct functions and characteristics.
What are the points of control in gene expression?
- DNA packing/unpacking
- Transcription
- mRNA processing
- mRNA transport
- Translation
- Protein processing
- Protein degradation
What is the transcriptome?
The set of all mRNAs produced from a genome, reflecting genes that are actively expressed at any given time.
What is the proteome?
The set of all proteins produced under a given set of conditions, reflecting genes that are actively expressed.
What is feedback inhibition in gene expression?
A process where enough product is made, causing the system to shut down to prevent overproduction.
Fill in the blank: The _______ is a region of DNA that can regulate transcription, typically inhibiting transcription.
Operator
What is the significance of the 5’ cap and poly-A tail in mRNA?
They determine whether translation takes place and how long the mRNA is active.
What is the primary function of transcription factors?
To increase or decrease the rate of transcription by binding to specific DNA sequences.
What are the sources of signals that affect the epigenome?
Sources include:
* Inside the cell
* Neighboring cells
* Environmental factors
Early in development, most signals come from within cells or neighboring cells.
What are epigenetic marks?
Similar to bookmarks that tell the cell what genes to express or silence
They can indicate whether genes are on, poised, or off.
What is histone acetylation?
The addition of acetyl groups to histones
It allows transcription factors to bind to DNA and promotes transcription.
What is DNA methylation?
The addition of methyl groups to DNA
It blocks transcription factors and inhibits gene expression.
What are imprinted genes?
Genes that are under greater selective pressure due to only one copy being active at a time
Variations in the active copy will be expressed without a backup copy to mask effects.
What effect does age have on epigenetics in identical twins?
As twins age, differences in their environments lead to changes in their epigenetics
This causes physical differences that can be studied.
What is the lac operon?
A cluster of genes involved in the metabolism of lactose
Lactose can cause upregulation of the lac operon.
What is the tryptophan operon?
A cluster of genes involved in the production of the amino acid tryptophan
Tryptophan can cause downregulation of this operon.
Fill in the blank: Epigenetic changes can be inherited through _______ cells.
germline
What does mRNA lifepsna depend on?
- chemical modifications
- presence of stabilising proteins
- activity & abundance of nucleases
- cellular stress (exposure to toxins)
Ostradiol function
A steroid hormone that targets cells with ostradiol receptors
- conformational change inside cell
- activated= moves into nucleus & binds to DNA sections => modifies gene expression
