Test 3 Flashcards
Differences in miRNA and siRNA and functions
micro RNA and short interfering RNA both regulate gene expression (=function). They are both structurally similar to each other however,,
miRNAs
- genomically encode non coding RNAs that reguate gene expression particularly during development
- tends to be more divergent in sequence and induce translational repression.
siRNAs usually are perfectly complementary to their target gene and induce direct mRNA clevage by RISC
Which proteins form a replisome? list them and their functions
Topoisomerase - corrects overwinding
Helicase - unzips parental double helix
SSB - single strand binding proteins - stabilises single DNA strands to be used as templates
Primase - synthsise RNA primer
Describe the structure of tRNA and its role in translation
Structure - polynucleotide of about 60-95 nucleotides long, exhibit a cloverleaf like secondary structure consisting of a stem and 3 main loops. Also display a tertiary L-like structure which interacts with ribosomes .
Role - act as an adapter between nuclotids, codons and amino acids. They pick up free amino acids in cytoplasm and carry them into the ribosomes where polypeptide chain is elongated.
What causes and are the symptoms of obstructive jaundice? which compound is used as a diagnostic marker in this case, what type of Van den Bergh’s test would be suitable
caused by blockages of the bile duct often by gallstones or by pancreatic cancer or ‘liver flukes’.
The presence of pale stools and dark urine suggests an obstuction of bile duct (yellow skin and eyes)
Lack of urobilinogen in urine is an indicator that no bilirubin is reaching the intestines
Direct Van den Bergh’s test gives positive and high values
Desribe the role of magnesium in the body, symtoms of its deficiency and connected diseases in different animal species
Role
1. one of the most common cofactors in the body
2. energy supply : ATP binds to Mg2+
3. Regulates muscle contraction
4. Affects Ca2+ homeostasis by surpressing actions of PTH
5. Reduced extracellular Mg conc increases membrane excitability in tissues such as heart
symptoms- muscle spasms and cramps, insomnia, chronic fatigue syndrome, restless leg syndrome, nausia and vomiting & death
Diseases - grass tetany in cows or hypomagnesaemia in sheep
Describe the principal of the method used during practicals to measure the concentration of Ca2+ in blood serum
-Based on titration of a sample solution with disodium EDTA.
- the indicator used is calcein
- the calcein forms a bright green colour with Ca ions
- during titration, the titrate sequestrates the Ca2+ ions releasing them from calcein complex.
-bright pink colour signals the the end point has been reached
What is snRNA? In which molecular process are these molecules involved and what is their role
snRNA - small nuclear RNA
- one of the main regulatory RNA molecules.
- components of a spliceosome
-involved in RNA splicing along with snoRNA (small nuceolar)
-sliceosome involves complex of 5 snRNAs
What is the difference in leading and lagging strand during DNA replication
Since DNA strands are anti-parallel, replication proceeds only in the 5 to 3 direction. The lagging strand forms a continuous copy while the other lagging strand forms discontinuous short DNA called okazak fragments
Describe the stages of transcription
Initiation
Does not need a primer to start
RNA polymerase simply binds ti DNA along with cofactors unwinds DNA and begins
Does require a promotor like sequence
Elongation
One strand of DNA, called template stand is used as a template for RNA synthesis
Uses base pairs complementary to create
RNA ploymerase traverses the template strand form 3 - 5 synthesising in RNA molecule from 5-> 3
Termination
occurs with a stop codon
signal is generally a G-C rich palnorome forming a local stem-loop, followed by the polymerase falling off
Describe the stages of translation
Initiation
Begins with binding of the small ribosomal subunit to a specific sequence on the mRNA chain
Once the subunit has bound, a special tRNA recognises and binds to the initiatorcodon
Large subunit binds forming initiation complex
Elongation
An aminoacyl tRNA with complemantary anticodon sequence can bind to the mRNA passing through the A site - a peptide is formed
Peptide chain shifts to the A site. The tRNA in A site becomes peptiacyl RNA and shifts to P site
Temrination
arrives when stop codon is reached
the eRF binds to the A site causing the realease of the polypeptide chain
What causes haemolytic jaundice? symptoms, causes, VDB test
caused by anything which causes an increased role of hemolysis like malaria and sickle cell anaemia
Urobilin levels in urine likely to be elevated in the blood and urine. indirect Van den Berghs test gives positive and high values
Describe the role of phosphorus in the body and deficiency
Component of bones, cartilage and crusacean exoskeleton
Essential component of phospolipids, nucleic acid, ATP
Central role in energy and cell metabolism
Inorganic phosphate serve as important buffers to regulate normal pH
Activation/ inactivation of many intercellular enzymes
Cage layer fatigue syndrome - in chickens
Symptoms - poor appetite, anxiety, irratability, reduced eggshell activity, reduced feed efficiency, lower body weight, skeletal problems
Detection of bile pigments
The qualative methods to detect bile pigments is Gmelins test. The main bile pigment is bilerubin which is easily oxidised by HNO3, iodine and other oxidising reagents. Gmelins test uses HNO3 and bile in a test tube and a formation on the border.
Describe the role of calcium in the body and deficiency
essential component of bone, cartilage and crustacean exoskeleton
activator for several key enzymes inc ATPases
Essential for the nromal clotting of blood
Ca2+ second messanger in cells
Along with phospholipids, plays an important role in regulation of the permeability of cell membranes
stimulates muscle contractions and regulates transmission of nerve endings
Differences in stationary phase, mobile phase and retardation factor in thin layer chromatography
Stationary phase - when the sheet of glass, plastic or aluminium foil is coated with a thin layer of absorbent material, usually silica gel, aluminium oxide or cellulose. This layer is known as stationary phase
Mobile phase - A solvent or solvent mixture is drawn up the plate via capillary action. Because different analytes ascend the TLC plate at different rates, separation is achieved.
Retardation factor (Rf) of each spot can be determined by dividing the distance travelled by the product by the total distance by the solvent
