1.4 Genes and Phenotypic Expression Flashcards
What are the two key parts that play a role in determing what genes are expressed
Cell differnetiation and Day to changes (e.g. environmental conditions may increase the expression of certain gene products when neded
Explain cell differentiation
cells all begin as identical clons able to become any type of cell, then differentation occurs, making the cells specific, with more genes expressed that are suited to their purpose
What causes differences between our cells
The differences are brought about by the types of proteins each different type of cells produces.
What is it called when a gene makes a protein
Gene expression
Why do different cell types produce different proteins
Due to genes in their DNA being turned on and off
Are some genes expressed constantly in all cells?
Yes - e.g. genes involved in cellular respiration
Will all genes be expressed in all cell types?
No
Does the rate at which genes are expressed vary?
Yes
What two things cause gene regulation (rate at which genese are expressed)
DNA methylation and histone modification
Why does DNA methylation and histone modification impact gene regulatio
They both cause changes in the coiling of DNA around a histone
What is Chromatin in simple terms
A double stranded helical structure of DNA
DNA is complexed with histones to form ……..
Nucleosomes
Coiling DNA around histones allows the gene to be….
either expressed or not expressed
What does a tighter wrap of the DNA around a histone result in
It restricts the ability for the gene to be expressed, hence reducing the amount of gene product produced
What does a looser wrap of the DNA around a histone result in
Results in the DNA more likely to be expressed
Does DNA wrap differently around histones for different cells?
Yes - this reults in differences as to which genes are expressed
What is DNA methylation
A process in which methyl groups are added to the DNA molecule
What does DNA methylation achieve?
DNA methylation can change the activity of a DNA segment without changing the sequence
When located in a gene promoter, what does DNA methylation typically do?
Typically acts to repress gene transcription
What can methyl groups added to the DNA promote?
The attachement of proteins to the DNA (such as histones, leading to wrapping and inaccessibility of that section)
What is one way methylation alters transcription
the Methylation of CpG islands way prevent or enhance the binding of regulatory transcription factors to the promoter region
What happens when CpG-binding proteins bind methylated sequences
Transcription is inbited
What other protein does methyl Cpg-binding protein recruit to convert the cromatin to a closed conformation
Histone deacetylase
What does the methylation of DNA and histones cause
causes nucleosomes to pack tightly together, meaning transcription factors cannot bind to the DNa and genes can not be expressed
What is the result of histone acetylation
Loose packing of the nucleosomes, meaning transcription factors cen bind to the DNA and genes are expressed
what is epigenetics
The study of changes to the DNA that ocur after differentiation has occured. E.g. differeneces in how gene expression occurs,
What is epigenetics NOT the study of
Mutations
Give one example of epigenetics
The wrapping or methylation of the DNA sequence
Is there evidence to suggest lifetsyle choices can lead to these changes?
Yes
What can a high fat diet cause
Certain genes to be over-methylated, leading to a reduction in expression
What could a reduction in expression of a certain gene caused by over-methylation lead to
Majpr problems as your cell may not be able to express that gene and make required proteins or reduce the rate at which it’s expressed, leading to a significant impact in overall health
If certain genes aren;t expressed due to epigenetics, what could happen?
Processes that organisms have inplace to manage diseases could potentially be limited/stopped/hindered
Give an example of what could happen if an important cell is hyper-methylated
If genes that suppress tumour formation due to being hyper-methylated due to environemental or other factors, it is more likley that a tumur will form and cause cancer
Epigenetic mechanisms are essential for normal development and …
maintenance of tissue specific gene-expression patterns in mammals.
What can the disruption of epigenetic proccecesses lead to
altered gene function and malignant cellular transformation
The intiation and progression of cancer, traditionally seen as a gentic disease, is now realised to involve…
Epigentic abnormalities as well as genetic alterations
The reversible nature of epigenetic aberrations has led to the emergence of
Epigenetic therapy, which is already making progress with the recent FDA approval of three epigenetic drugs for cancer treatment
There is some evidence to suggest that epigenetic changes can be passed onto the next generation. What does this mean?
children could inherit the negative impacts of a parent’s diet/life choices
