Year 13 - Gene expression Flashcards
Describe the following biological terms and when they are found as per the spec:
- Stem cells
- Totipotent
- Pluripotent
- Multipotent
- Unipotent
Stem cells- cells that can divide by mitosis into two genetically identical cells. One remains as stem cell and the other differentiates into a specialised cells by translating part of their DNA.
Totipotent- divide and differentiate into any type of cell and can produce a whole new organism. Found up to 8 cell stage in early mammalian embryos for a limited time.
Pluripotent- divide unlimited times and differentiate into any type of cell. Found in an embryo.
Multipotent- divide a limited number of times and differentiate into a limited number of different cell types. Found in mature mammal tissues eg bone marrow.
Unipotent- divide a limited number of times and differentiate into one cell type. Found in the heart as cardiomyocytes.
Suggest how ’molecule’ increasing gene expression works
->molecule is a Transcription factor
->binds to promotor region in DNA as complementary
-> stimulates RNA polymerase
-> transcription.
Describe how oestrogen acts as a transcription factor
- Oestrogen is lipid soluble so diffuses through phospholipid cell surface membrane and nuclear envelope.
- Oestrogen is complementary to oestrogen receptor so binds.
- This changes tertiary structure of PROTEIN RECEPTOR (NOT OESTROGEN AS THIS IS NOT A PROTEIN)
- Releasing the transcription factor
- Transcription factor is complementary to a specific sequence of DNA known as the promotor region so binds
- Stimulates RNA polymerase to transcribe the gene, increasing transcription so mature mRNA is produced.
How do interfering RNA (RNAi eg siRNA and miRNA) work?
- siRNA/miRNA is specifically Complementary to named genes/protein’s mRNA
- So binds by H bonds
- Results in destruction of mRNA OR stops ribosome binding to mRNA so stops translation initiating.
- So reduces translation of named protein
- So reduces named protein in cell so less named protein function
Define epigenetics
Heritable changes in gene function without changes to the base sequence of DNA
Describe and explain the epigenetic modifications that keep genes turned off.
- Increased methylation of DNA means named transcription factor can’t bind to promotor region of DNA
- Decreased acetylation of histone protein tails (more tightly packed)
- less expression of gene
- so less RNA polymerase binds to DNA next to promotor
- less mRNA of named gene produced
- less named protein
- less named proteins function
Describe and explain the epigenetic modifications that keep genes turned on.
- Decreased methylation of DNA means named transcription factor binds to promotor region of DNA
- Increased acetylation of histone protein tails (loosely packed)
- more expression of gene
- so RNA polymerase binds to DNA next to promotor region
- transcribes *named gene8 producing more mRNA
- so more named protein
- so more named protein function
