BM210 Flashcards
(22 cards)
Describe transcription factors
A sequence specific DNA binding protein which helps regulate transcription initiation
Where are missense mutations found within the gene?
Exon regions
In which region of the gene is there an enrichment of CpG islands?
Promotor region
Describe epigenetics and give an example
Modifications to the genome that affect gene expression but do not alter the DNA sequence
eg: DNA methylation
Describe DNA methylation
The addition of methyl groups to nitrogen bases of nucleotides (mainly cytosine).
DNA methylation regulates gene expression by gene silencing, by inhibiting the binding of transcription factors to DNA or recruiting proteins involved in gene repression.
What role do CpG islands play in gene expression?
CpG islands undergo chemical modifications which alter binding of transcription factors
Which enzyme methylates the cytosine in CpG islands?
DNMT (DNA Methyltransferase)
Describe the 2 chromatin states
Euchromatin: Loosely packed, enriched in genes
Heterochromatin: Tightly packed,
genetically inactive
What is the start and end sequence of all introns?
Begin with GU and end with AG
Describe alternative splicing?
A process where different mRNAs are generated from the same primary transcript, thereby generating proteins with different functions
Describe the 2 mechanisms of cell communication
Intercellular signalling:
- Communication between cells
- Eg: synaptic transmission
Intracellular signalling:
- Signalling within the cell
- Eg: generation of second messengers
Describe autocrine signalling and give an example?
Cell targets itself, synthesising a soluble ligand that is then released
Eg: Il2
Describe paracrine signalling and give an example?
Cell targets nearby cells, generating a signal resulting in a mediator being released.
Eg: the release of chemokines by neutrophils, which attract other cells by chemotaxis
Describe endocrine signalling and give an example?
Hormone dependent mechanism where the signalling cell targets a distant cell through the bloodstream.
Eg: the liver is an endocrine gland due to the secretion of insulin
Describe the bonding present in Starch
Amylose - Alpha 1,4 glycosidic (Unbranched)
Amylopectin - Alpha 1,4 with Alpha 1,6 branches (tightly packed)
Describe the bonding in glycogen
Alpha 1,4 glycosidic bond with lots of Alpha 1,6 branches (compact)
Describe the bonding in cellulose
Beta 1,4 glycosidic bond (unbranched, straight fibrous chain)
Describe the gene to protein formation
- Enzymes break H bonds between bases, unwinding the helix
- RNA polymerase builds a complimentary strand of mRNA using nucleotides from the nucleus
- The mRNA template leaves nucleus to ribosome
- tRNA transports amino acids to ribosome
- Peptide bonds form between amino acids to form poly peptide chain
What are the key steps involved in the activation of PKB in target cells by insulin?
Insulin binds to its receptor (IR) which is a tyrosine kinase, this leads to receptor auto-phosphorylation.
The phosphorylated insulin receptor acts as a docking site for insulin receptor substrate proteins (IRS).
The receptor phosphorylates IRS, which then recruits the lipid kinase, phosphoinositide 3-kinase, which converts PIP2 to PIP3.
Binding to PIP3 activates PDK1, which then phosphorylates and activates PKB.
Explain GLUT4 and which type of transport it is?
A carrier protein which transports glucose, through facilitated diffusion which is passive transport
when insulin is present, glut4 inserts into fat and muscle cells
glucose then binds to glut4 which results in conformation shape of carrier protein
glucose is released inside cell
Describe the function of histone proteins
Histones are highly basic proteins which are positively charged, this allows them to associate with DNA which is negatively charged. DNA wraps around histone proteins in order for it to condense and package correctly within the nucleus.
Name 2 second messengers?
cAMP and Ca2+
