Topic 1 (Genomes) Flashcards
How many Autosomes
22
Which autosome is the biggest?
1
Which type of cells copy without dividing? (In terms of N?)
Megaokaryocytes
4n
Barr bodies
Inactivated X chromosome
Xist
microRNA regulatory RNA
Inactivates X chromosome
What is synteny
Long DNA sequence present in same order across species
give an example of synteny
X + Y across man / mouse
Which cells host translocations
Germ cells
What disease can arise from translocation
Which chromosomes are involved?
Philadelphia Chromosome (Chronic Myeloid Leukaemia) 9--> 22
How are pseudogenes formed? (2)
Gene Duplication // Reverse Transcriptase
How does RT play a role in pseudogene formation?
No promotor upstream therefore no transcription
How does gene duplication play a role in pseudo formation
gene mutations can occur from duplication = inactive
What is the name of repeated short sequences?
Variable Number Tandem Repeats
What causes VNTR
Slippage of Polymerase
Name a disease that can arrise from VNTR
Huntingtons Disease
How does Huntingtons Disease occur from VNTR
Increased #CAG codons = abnormal glutamine residues
neuron degeneration
GWAS
Genome Wide Association Studies
ANRIL
Non coding RNA that can contribute increased risk of heart disease // diabetes
Polysome
mRNA covered in chain of ribosomes
Cytosol
thick liquid / gel surrounding organelles
Cytoplasm
Cytosol + Organelles but no nucleus
Where are nuclear proteins synthesised?
In cytosol
Transported back into nucleus
Where are mitochondrial proteins made?
Made by polysomes in cytoplasm
Imported into mitochondria
What does RNA polymerase 1 do
Transcribes Ribosomal RNA
What does RNA polymerase 3 do
Transcribes tRNA
What can be present in mitochondria to translate mRNA
Mitochondrial ribosomes
Give an example of a promotor element
TATA box
What does the TATA box produce? Why does it produce these nucleotides (2)
Lowest energy base pairing
Easiest to unwind
How far back can a TATA box be
25bp
Whats the difference between ribose and deoxyribose
ribose - OH on C2
deoxyribose - H on C2
RNA polymerase 2 is involved with what?
Transcription of mRNA
What allows RNA polymerase 2 to bind to template strand
Transcription factors bind to promotor region (TATA)
What are distal elements
Stretch proximal enhancers / silencers
When are distal elements used in
Tissue specific regulated transcription
With CpG islands, what does these islands protect from
Cysteine is protected from methylation
If methylation of a CpG islands occurs, what happens?
turning off expression of a gene
When does methlyation of CpG islands occur?
In inactivation of X chromosome
What does CpG islands mysteriously transcribe?
non-coding RNA
how many AA are added in poly A tail
150-250
What protein doesnt have a poly A tail
Histone
Amino acid involved with capping.
what prime end?
Glycine
5’
What is the loop called in splicing
Lariat
Polycistronic
when a particular gene codes for more than one protein
Where is the GU nucleotide found
3’ upstream of intron
Where is the AG nucleotide found
5’ downstream of intron
B globin is regulated by what?
Locus Controlling Region (LCR)
How does the LCR work?
Forms a loop / self containing unit
Allows expression of particular genes within Locus
The stretch of amino acids that attaches to ribosome is called what?
Whats special about it?
How many AA are there?
Signal sequence
Hydrophobic
20AA
What does the signal sequence cause the ribosome to do?
Bind to the ER
What is cut off in the lumen of ER with translation?
Signal sequence (N terminus)
How are transmembrane proteins formed?
Examples of AA
Stretch of 20 Hydrophobic AA embed in bilayer
Valine , Alanine , Leucine
What happens in RER with bridges / sugar chains /protein folding
ER proteins folded
Disulphide bridges formed from cysteine
Sugar side chains added
What type of secretion would be Beta cells + insulin be?
Regulated Secretion
What type of secretion would be the liver
Continuous secretion
What causes a vesicle to go to a lysosome
Addition of a phosphate to mannose in ER
What are the 3 stages of insulin
Preproinsulin
Proinsulin
Insulin
What happens with preproinsulin
Signal sequence cut off in ER
Leaving inactive chain
What happens with proinsulin
Disulphide bonds form between A + B chain
What happens with insulin
C chain peptide cleaved away by proteases
to form active form
If an nucleotide changes the entire AA sequence leading to a no active protein, what mutation is this called?
Frameshift Mutation
