Gene expression Flashcards
What is a stem cell?
An undifferentiated cell that can become specialised
What are the 3 types of stem cells + what do they do?
- Totipotent = develops into any type of cell
- Pluripotent = develops into any cell apart from the placenta or embryo
- Multipotent = only develops into a few different types of cells
What is a unipotent cell + give an example?
Only develops into one type of cell
E.g. heart cell
What are some uses stem cells?
Medical therapy
Drug testing on artificially grown tissues
Research
How are induced pluripotent cells produced?
From fully specialised somatic cells
Cell can differentiate through the use of protein transcription factors
How do transcription factors work?
- Move from the cytoplasm to the nucleus
- Bind to the promoter region
- Changes difficulty of RNA polymerase binding to gene which affects the rate of transcription
Explain how oestrogen affects transcription
- Oestrogen diffuses through membrane
- Forms hormone-receptor complex with ER receptor in cytoplasm
- Complex acts as transcription factor in the nucleus, facilitating the binding of RNA polymerase
Define epigenetics
A heritable change in gene function without without a change in the base sequence of DNA
How does increased methylation of the DNA affect gene transcription?
Addition of a methyl group cytosine bases
Prevents transcription factor binding
Therefore suppressing gene transcription
How does decreased acetylation of the DNA affect gene transcription?
Positively-charged histones bind to negatively charged DNA
Decreased acetylation increases positive charge of histones
Tight binding prevents transcription factors from accessing the DNA
Therefore suppressing gene transcription
Describe the process of RNA interference
- RNA molecules inhibit gene expression
- Destroys mRNA so it cannot be translated
Occurs in eukaryotes + some prokaryotes
What are some of the differences between benign and malignant tumours?
Benign: Malignant:
Slow growth Rapid, uncontrollable growth
Don’t spread easily Spread easily
Easy to treat Difficult to treat
How are tumour suppressor genes involved in developing cancer?
- Mutation in the gene could code for a non-functional protein
- Increased methylation + decreased acetylation could prevent transcription
- Cells divide uncontrollably, resulting in a tumour
How are proto-oncogenes involved in developing cancer?
- Mutation in the gene could permanently activate the oncogene
- Decreased methylation + increased acetylation causes excess transcription
- Results in uncontrolled cell division, forming a tumour
How does abnormal methylation cause cancer?
Hypermethylation of tumour suppressor / oncogenes impair their function
This causes the cell to divide uncontrollably
