Mutation + Gene Expression Flashcards
What are mutations
Changes in DNA base sequence
What can insertion or deletion mutations cause
Frameshift
What is a duplication mutation
One or more bases are repeated producing a frame shift
What is an inversion mutation
Group of bases become separated and Rejoin at same position in reverse order
What is a translocation mutation
Group of bases separated from DNA on a chromosome and inserted into DNA sequence of another chromosome
Name 3 causes of mutation
Spontaneous in DNA replication
Chemical mutagens
Ionising radiation
Why might a mutation not cause a change in amino acid produced
DNA is degenerate
Mutation in Intron/non-coding part of DNA
Why might a mutation that changes a Amino acid not have an effect on function of protein
Change in tertiary structure does not affect active site
What is a stem Cell
Undifferentiated cells which can divide to give rise to any cell type
Totipotent stem cells
Can differentiate into any cell type including embryonic cells
- only around during early stage of embryo then and quickly differentiate to make up foetus
Pluripotent stem cells
Can form any cell type in body except embryonic cells
Multi potent stem cells
Can differentiate into multiple cell types but are more limited
Unipotent stem cells
Only differentiate into one type of cell
What can stem cells be used for in health
Treat disease by repairing damaged tissue or differentiating into cell types to replace damaged
What are Induced pluripotent cells
Come from Unipotent cells eg: skin
Reprogrammed back into unspecialised Pluripotent cells by activating genes using Transcription factors
Why are Induced pluripotent cells useful
Reduces need to extract Pluripotent cells from embryo
Reduces ethical concern of embryo use
Reduce chance of rejection as its own body cells
What happens when a cell becomes specialised
Only some genes are activated = only activated genes are expressed
If a gene is expressed it is transcribed and translated to produce proteins = differentiation happens as certain proteins are made
The presence of certain proteins makes a cell soecialised
What is a gene
A section of DNA that can be transcribed into a protein
What are transcription factors
Produced in cytoplasm + move to Nucleus
Stimulate or inhibits transcription of target genes
How do transcription factors activate or repress transcription
Interact with RNA Polymerase = allowing it to bind to DNA
Or Stops RNA polymerase from binding
What allows Oestrogen to move freely across cell membrane
Lipid-Soluble Hormone
Describe the action of Oestrogen in initiating Transcription
1- Binds to Receptors on Transcription factors in cytoplasm
2- forms a Receptor-Complex Hormone that can now enter the nucleus
3- bind to promoter Region of DNA = stimulates Transcription
What does Oestrogen do to allow transcription factor to bind to DNA
Binding changes the shape of the DNA binding site on the transcription factor = means it can bind to DNA
What is siRNA
Small interfering RNA
Small double stranded = unwinds to form a single strand complimentary to mRNA
Prevents translation by breaking down transcribed mRNA
How does siRNA break down/ cut up mRNA
1- siRNA binds to complimentary sequence on mRNA
2- as mRNA is meant to be single stranded cell detects double strand and views it as Abnormal
3- mRNA is therefore broken down preventing translation
*siRNA has to unwind to become single stranded
* mRNA is cut into small fragments
What are epigenetics
Gene expression is controlled without changes to base sequence of DNA - shows that environmental factors can affect function of genes
What is methylation and the effect of increased methylation
Methyl groups added to DNA
Prevents transcriptional factors from binding to DNA by making it tightly wound round histones = factors cannot bind so no transcription
What is acetylation and what is the effect of decreased acetylation
Adds acetyl groups to histone
Histones are positively charged and DNA is negatively charged = decreased acetylation increases positive charge on histones = DNA bound more tightly = factors cannot access DNA = no transcription + gene switched off
To decrease the transcription/ switch off genes what epigenetic changes occor
Increase methylation
Decrease Acetylation
What is cancer
Uncontrolled rapid cell division
Benign tumours
Grow slowly and dod not spread = does not invade nearby tissue
However does put pressure on body by pressing against blood vessels or other cells
Malignant tumours
Grows rapidly and spreads to nearby cells = cause damage by damaging bayou tissues + organs
Much more difficult to treat than benign
What is metastasis
Cancer cells break off from tumour and travel through blood + lymphatic system
What are proto-oncogenes
Stimulate cell division = produce proteins that cause cells to divide
Produce oncogenes if mutated
What are oncogenes
Formed from mutated Proto-Oncogenes
= results in genes for cell division permanently switched on = uncontrolled cell division
Tumour suppressor Genes
Control/ Slow cell division
= produce proeteins that stop cell division
Also play a role in Apopstasis= programmed cell death
When TSGs are switched off cell division is unregulated
How might hypermethylation affect tumour suppressor genes
No proteins to control cell division produced = cell division is uncontrolled
How might increased oestrogen levels be linked to cancer
Increased formation of receptor-Hormone complex with transcription factors = increased activation of genes promoting cell division = uncontrolled cell division
How might hypo methylation affect Proto-Oncogenes
Removal of methyl groups = proto-oncogenes act as oncogenes and cell division is stimulated
Increase in transcription of proteins that cause cell division
How do environmental factors such as smoking affect Epigenetics and cancer/tumours
Environmental factors affect methylation
Methylation can cause tumour suppressor genes to be silenced or oncogenes to be activated = causing tumour formation
Scientists are developing drugs to reverse Epigenetic changes
