D2.2 Gene Expression Flashcards
Phenotype
The functional and structural characteristics of an organism.
Genotype
All the genetic information of an organism.
Gene expression
The process of turning genotype into phenotype by protein synthesis.
Promoters function
A sequence of DNA located upstream of a gene in the 5’ direction, ensure that RNA polymerase transcribes the gene in a 5’ to 3’ direction.
Transcription Factors
Proteins that bind to specific base sequences of DNA and regulate gene transcription.
What happens to mRNA after it is no longer required for translation?
It is broken down by nucleases.
What are examples of protein synthesis in which DNA degradation regulation is important?
- Casein being produced for ling periods of time.
- Cyclins that are only needed briefly.
State the relationship between the length of a poly-A tail and its lifespan:
- Shorter = higher nuclease activity
- Longer = lower nuclease activity
Epigenesis
The development of a plant or animal from undifferentiated cells.
How does differentiation occur in the context of gene expression control?
Activating some genes and deactivating others.
Epigenetic tags
Chemical modifications of DNA that alter the phenotype of an organism.
Genome
Whole genetic information of a cell.
Transcriptome
The entire set of mRNAs transcribed in a cell.
Proteome
The entire set of proteins produced by a cell.
Methylation
The replacement of a hydrogen with a methyl group.
Role of the methylation of the promoter:
- Prevents the binding of some transcription factors so that RNA polymerase does not transcribe the gene downstream of the promoter and is not expressed (usually adenine and cytosine).
Role of methylation in histones of nucleosomes:
- Methyl can be added to an amino acid in histone proteins to activate or deactivate transcription.
Epigenome
All of the genetic tags of an organism.
What do epigenetic tags influence?
Gene expression and phenotypes.
: How do epigenetic tags change during a cell’s life?
They change in response to environmental factors.
What happens to epigenetic tags during cell division?
They can be passed to daughter cells, helping them perform the same functions (this applied only to mitosis and NOT gametogenesis).
What was previously believed about epigenetic tags during meiosis?
They were thought to be removed, leaving a “blank canvas” in zygotes.
What recent evidence suggests about epigenetic tags?
Some tags are not removed and can be passed to offspring (transgenerational epigenetic inheritance).
How do epigenetic tags differ from base sequences?
Epigenetic tags can be easily changed, while base sequences are altered only by mutations.
What is an example of transgenerational epigenetic inheritance?
1% of epigenetic tags persist to the next generation.
Out of the blue
An epigenetic tag can prevent a dominant allele from being expressed.
What are environmental factors that can affect gene expression
Monozygotic Twins
Come from one zygote
Dizygotic Twins
Twins that come from two separately fertilized zygotes. (Share 50% of DNA)
How do environmental factors affect gene expression (lactase production):
- Absent: repressor proteins bind to the promoter of the lactase gene to prevent expression.
- Present: The repressor does not bind to the promotor, so it can bind to the lactase gene and start transcription.
How do environmental factors affect gene expression (oestrogen):
- Estrogen binds to a gene that produces progesterone receptor, and the endometrium becomes more responsive to progesterone.
