MGD * Flashcards
Briefly describe 2D-PAGE.
2D-PAGE is a variant of protein electrophoresis that combines SDS-PAGE and isoelectric focusing to separate complex mixtures of proteins according to their size and charge. This can be used to diagnose disease states.
Are cancer-causing alleles normally dominant or recessive?
Recessive
Briefly describe isoelectric focussing.
Isoelectric focusing is a variant of protein electrophoresis. The gel contains a pH gradient, so the proteins will move either up or down the gel depending on their charge, until they reach their isoelectric point at which point they will have no charge and will stop moving. Isoelectric focusing separates proteins based on their charge alone.
Briefly describe native gel electrophoresis.
Separates proteins on the basis of their size, shape and charge.
Briefly describe SDS-PAGE
Involves the action if a detergent (SDS) and reducing agents to denature the protein same, so the proteins are separated only on the basis of their size.
Briefly describe Southern blotting.
A technique used to transfer DNA fragments to a more permanent membrane after electrophoresis. A nitrocellulose sheet is placed on the gel and covered with paper towels. This is left for a period of time, after which the fragments have transferred to the nitrocellulose sheet.
Briefly describe Southern hybridisation.
Southern hybridisation combines DNA hybridisation with Southern blotting. The DNA fragments are separated by electrophoresis and then Southern blotting is carried out. The hybridisation is carried out on the nitrocellulose paper, and the positions of the specific DNA sequences can be visualised on exposure to photosensitive film/UV light.
Briefly describe Western blotting.
A technique used to transfer proteins from gel after protein electrophoresis to a more permanent membrane. A nitrocellulose sheet, which has antibodies on it’s surface specific to particular protein(s), is laid on top of the gel and covered in paper towels. The protein(s) bind to the antibodies.
Briefly outline the mechanism for targeting proteins destined for lysosomes.
A mannose-6-phosphate signal is added in the Golgi body which causes the protein to be transported to a lysosome.
Briefly describe the mechanism for targeting proteins destined for retention in the ER.
The proteins have a KDEL sequence which is recognised at the Golgi body and causes the protein to be transported back to the ER.
Briefly outline the mechanism for targeting proteins destined for the mitochondria.
The protein contains an amphipatic N-terminal sequence which is recognised by TOM proteins (transporter outer membrane) to cross the outer membrane and TIM proteins (transporter inner membrane) to cross the inner membrane. The proteins are not folded until they reach the inside of the mitochondrion.
Briefly outline the mechanism for targeting proteins destined for the nucleus.
The proteins contain a Nuclear Localisation Sequence (NLS). Proteins called importins bind to the NLS and the complex travels through a nuclear pore.
Define ‘recombination’
Where the crossing over between the loci of 2 linked alleles causes them to be separated from each other.
Define ‘activity’
A measurement of the amount of an enzyme, equal to the moles of substrate converted per unit time.
Define ‘allele’
A variant of a particular gene
What is aneuploidy?
Numerical chromosome abnormality in which the chromosome number is not a multiple of the haploid number. This can be monosomy or trisomy.
Define ‘complementation’ with regard to genetics.
Complementation occurs when expression of an allele at one gene locus is affected by an allele at another locus.
Define ‘dominant allele’
The allele in a heterozygote which determines the phenotype
Define gene
A length of DNA that codes for a protein
Define ‘isoelectric point’
The pH at which the protein has no nett charge.
Define ‘Km’
The concentration of substrate required to give a rate of reaction equal to 1/2 of Vmax
Define ‘linkage’
When the loci for two genes are on the same chromosome, those genes are said to be linked. How close the loci are on the chromosome determines how tightly linked they are - the closer the loci, the tighter the linkage.
Define ‘monosomy’
A type of aneuploidy in which an individual has lost one copy of a certain chromosome.
Define ‘oncogene’
A gene that can transform a cell into a cancerous phenotype.
How do you calculate pH?
pH = -log[H+]
Define ‘point mutation’
Change of one nitrogenous base for another
Define ‘polyploidy’
Numerical chromosome abnormality in which the chromosome number is a multiple of the haploid number greater than the diploid number, eg. triploidy and tetraploidy.
Define ‘proto-oncogene’
A gene that is very similar in sequence to an oncogene and can become an oncogene by mutation
Define ‘recessive allele’
The non-dominant allele in a heterozygote
Define ‘trisomy’
A type of aneuploidy in which an individual has gained one copy of a particular chromosome.
Define ‘Vmax’
The maximum rate of reaction that occurs when all sites are saturated with substrate.
Define ‘zymogen’ and give two examples.
An inactive precursor of an enzyme, which is activated by proteolytic cleavage. Examples include trypsinogen (converted to trypsin) and pepsinogen (pepsin)
Define co-dominance and five and example.
A co-dominant characteristic is one where both alleles contribute to the phenotype eg. blood group
What is the formula for the concentration of H+ ions
[H+] = 10^(-pH)
Define the ‘international unit of enzyme activity’
The amount of enzyme that catalyses the conversion of 1 micromoleof substrate to product per minute
Describe and explain the oxygen binding pattern for Hb
The oxygen dissociation curve for Hb shows a sigmoidal relationship between % saturation and partial pressure of oxygen. The Hb is in it’s T state, with a low affinity for oxygen, when it’s deoxygenated, but when the first molecule of oxygen binds it changes to it’s R state which has an increased affinity for oxygen, so subsequent oxygen molecules bind more easily. This cooperative binding gives rise to the sigmoidal oxygen dissociation curve.
Describe and explain the oxygen binding pattern for myoglobin.
The oxygen dissociation curve for myoglobin shows a hyperbolic relationship between % saturation and partial pressure of oxygen. This is because myoglobin only has one subunit so it doesn’t exhibit cooperative binding to oxygen.
Describe DNA hybridisation
DNA hybridisation involved adding DNA probes which have been fluorescently marked to a sample of DNA which has been denatured. The sample is then renatured and the probes anneal to complementary DNA sequences, allowing specific sequences to be detected.
Describe gene cloning
To carry out gene cloning you must first identify and isolate the desired gene using a restriction enzyme. You then get a sample of bacterial plasmids and add the same restriction enzyme to this sample. The desired gene is added to the plasmids and DNA lipase is added to make the plasmids take up the gene. The recombinant plasmids are then mixed with bacteria and a technique such as heat shock is used to make the bacteria take up the plasmids. The cells which have taken up recombinant plasmids are selected for by using antibiotics. These cells are then cultures so that the gene is cloned when they replicate.
Describe how nucleotides are bonded together in a nucleic acid.
Nucleotides are bonded by phosphodiester bonds. The phosphate group bonds to the -OH group on carbon-3
Describe in detail the features of a B-sheet
A B-sheet forms from fully extended strands of amino acids. The distance between each amino acid is 0.35nm. The R groups alternate on each side of the strand. The strands lie side to side and H bonds form between them, forming sheets. The sheet may be parallel if the strands all run in the same direction or antiparallel if they run in opposite directions.
Describe in detail the structure of an alpha helix
It’s a right-handed helix with a pitch of 0.54nm. There are 3.6 amino acid residues per turn of the helix. The R groups all face toward the outside of the helix, and the carboxyl and amine groups of each residue face in opposite directions. The helix is stabilised by H bonds between carboxyl and amine groups which are 4 amino acids away from each other.
Describe in detail the structure of tropocollagen
Tropocollagen is a right-handed triple helix consisting of 3 left-handed alpha chains twisted around each other. Every third amino acid in the chain is glycine with many other amino acids being proline, hydroxyproline or lysine. Tropocollagen is 300nm in length.
Describe phosphorylation and de-phosphorylation of an enzyme
Phosphorylation is carried out by kinase enzymes. A phosphate group is added to an amino acid with an -OH group. Phosphate groups have large negative charges and can form H bonds so they affect protein structure. De-phosphorylation is the removal of a phosphate group, carried out by phosphatase enzymes. Phosphorylation and de-phosphorylation may both either activate or inhibit an enzyme.
Describe restriction analysis
Restriction analysis involves the use of restriction enzymes. These are endonucleases that cut polynucleotides at particular base sequences called restriction sites. Restriction analysis involves mixing a particular restriction enzyme with a DNA sample and analysing the resultant fragments by electrophoresis. The fragments of different DNA samples can be compared to investigate if there has been a mutation that has added or removed a restriction site, for example.
Describe the action of a reversible competitive inhibitor
A reversible competitive inhibitor binds non-covalently to the active site of an enzyme and blocks it temporarily so that no substrate can bind to it. This decreases turnover rate and lowers Km, but Vmax is unaffected. The effect of competitive inhibitors can be overcome by increasing the substrate concentration.
Describe the actin of reversible non-competitive enzyme inhibitor.
A reversible non-competitive inhibitor binds non-covalently to a site on the enzyme which is not the active site and decreases the turnover rate. The effect of non-competitive inhibitors can’t be overcome by increasing substrate concentration. They affect Vmax but no Km.
Describe the action of an irreversible enzyme inhibitor
Irreversible inhibitors bind irreversibly to the enzyme and destroy it’s function.
Describe the activity of X chromosomes in a cell.
Only one X chromosome is ever active in a cell, any others form structures called Barr bodies at the periphery of the nucleus.
Describe the allosteric regulation of phosphofructokinase
PFK catalyses step 3 of glycolysis. This step is irreversible and is therefore a controlling step. PFK is allosterically activated by AMP and fructose-2,6-bisphosphate, it is allosterically inhibited by ATP, citrate and H+
Describe the binding of 2,3-bisphosphoglycerate to Hb
One molecule of 2,3-BPG binds to each Hb molecule. 2,3-BPG binds in the centre of the tetramer to positively charged residues.
Describe the bonds responsible for secondary structure of proteins.
The secondary structure is entirely determined by H bonds between the H of the NH part of a peptide bond and the O of the C=O part of a peptide bond)
Describe the cause of thalassaemia
Caused by an imbalance in the number of alpha and beta subunits of Hb. This can be alpha thalassaemia, where not enough alpha subunits are produced, or beta thalassaemia, where not enough beta subunits are produced.
Describe the cell cycle
Starting at the beginning of interphase. G1 is the first phase of interphase. During G1 the components of the cell duplicate. After G1 there is a cell cycle checkpoints during which it’s checked that G1 has been successfully completed. Then there is S phase in which DNA replicates, followed by G2 in which the DNA replication is checked for errors and any errors are repaired. After G2 there is a second cell cycle checkpoint in which the cell can decide whether to replicate or not. If the cell is going to replicate, G2 is followed by mitosis and then cytokinesis. The 2 daughter cells begin at G1.
Describe the concept of enzyme cascades.
Enzyme cascades involve one enzyme which activates another enzyme, which activates another enzyme and so on. Each enzyme can activate multiple other enzymes. This means the number of affected molecules can increase by orders of magnitude. Usually the enzymes catalyses phosphorylation/dephosphorylation of the next enzyme.
Describe the difference between the constitutive and regulated secretory pathways.
In the constitutive secretory pathway the protein is continually being synthesised, packaged into vesicles and released by exocytosis. In the regulated secretory pathway the protein is packaged into vesicles but the vesicles aren’t released until a stimulus is received.
Describe the differences in structure between Hb and myoglobin
Hb consists of 4 polypeptide subunits, normally 2 alpha and 2 beta subunits, with a haem group bound to each subunit. Myoglobin consists of a single subunit with a haem group attached.
Describe the different physiological roles of Hb and myoglobin
Hb is present in erythrocytes. It’s role is to pick up oxygen at the lungs and transport it to the tissues where it’s needed for aerobic respiration. Myoglobin is present in muscles. It’s role is to store oxygen for when oxygen is scarce in the muscle so that aerobic respiration can continue to occur.
Describe the effect of 2,3-BPG on the binding of oxygen by Hb and the physiological significance of this effect.
2,3-BPG decreases the affinity of Hb for oxygen. This is significant because it makes oxygen transport more efficient as it increases the amount of oxygen deposited at the tissues. The amount of oxygen picked up at the lungs is relatively unaffected as the lungs have such a high partial pressure of oxygen.
Describe the effect of CO on the binding of oxygen by Hb and the physiological significance of this effect
CO affects oxygen transport by Hb in two ways; by binding irreversibly to haem groups and in binding, increasing the affinity of Hb for oxygen. This means oxygen is prevented from binding to Hb and also less oxygen is released at tissues. CO poisoning can be lethal.
Describe the effect of CO2 on the binding of oxygen by Hb and the physiological significance of this effect
High concentration of CO2 decrease the affinity of Hb for oxygen as the CO2 molecules bind to the Hb molecules. This is called the Bohr effect. It ensures that oxygen is released at metabolically active tissues, which release a lot of CO2.
Describe the effect of H+ on the binding of oxygen by Hb and the physiological significance of this effect
High concentrations of H+ decrease the affinity of Hb for oxygen as the H+ molecules bind to the Hb molecules. This is called the Bohr effect. It ensures that oxygen is released at metabolically active tissues, which release H+
Describe the elongation stage of transcription
RNA polymerase travels along the DNA template strand in the 5’ to 3’ direction, adding complementary RNA nucleotides. A nearly identical copy of the coding strand is produced.
Describe the elongation stage of translation
Elongation begins with Met-tRNA in the P site of the ribosome. The ribosome has two sites where tRNA can bind, the P site and the A site. An aminoacyl-tRNA molecule, with a complementary anticodon to the next codon in the sequence, binds to the A site. The amino acid from the aminoacyl-tRNA binds to the methionine on the Met-tRNA molecule, catalysed by peptidyl-transferase, and the methionine moves over to the amino acid attached to the A site. The tRNA molecule at the P site is now empty and it leaves the ribosome. The tRNA in the A site, with it’s attached polypeptide, moves over to the P site. Another aminoacyl-tRNA moves into the A site and the process repeats to elongate the polypeptide chain.
Describe the formation of the mature insulin molecule
Insulin is initially synthesised as pre-proinsulin in the ER lumen. This consists of the signal peptide and peptides A, B and C. The signal sequence is removed by signal peptidase in the ER lumen, and 3 disulphide bonds form with 2 between peptides A and B. This gives proinsulin. Proinsulin undergoes further proteolytic processing in the Golgi body and the C peptide is cleaved, leaving the A and B peptides joined by disulphide bonds. This is mature insulin.
Describe the general concept of enzyme assays
Enzyme assays measure the activity of an enzyme in a sample. To carry out an enzyme assay you add saturating amounts of substrate under optimum conditions and measure the disappearance of substrate or the appearance of product.
Describe the initiation stage of transcription.
A ‘TATA box’ sequence upstream of the gene is recognised and bound to by transcription factors. RNA polymerase then binds to the site and separates the DNA strands.
Describe the initiation stage of translation
The 5’ cap on the mRNA molecule is recognised and bound to by cap binding proteins, initiation factors and the small 40s ribosomal subunit. The 40s subunit has Met-tRNA bound to it. The 49s subunit then moves down the mRNA molecule until it reaches a start codon (AUG, which codes for methionine). The 60s ribosome subunit then binds, forming a functional ribosome which can carry out the elongation stage.
Describe the key features of the DNA double helix
The strands in the double helix run antiparallel to each other and are bonded to each other by H bonds between complementary base-pairs. The pitch of the helix is 3.4nm. The helix has a major groove and a minor groove, with the major groove being longer in height and shallower than the minor groove.
Describe the mechanism of allosteric regulation
Allosteric enzymes have multiple subunits and exist in two states, the T state (has a low affinity for the substrate), and the R state (has a high affinity for the substrate). A graph of rate of reaction/substrate concentration for an allosteric enzyme shows a sigmoid relationship. Allosteric activators bind to the R state and stabilises it, so the enzyme has a high affinity for the substrate. Allosteric inhibitors bind to the T state and stabilise it, so the enzyme has a low affinity for the substrate.
Describe the middle stage of DNA replication. What is this stage called?
The DNA double helix unzips, catalysed by helicase, as the replication fork moves along. One strand of DNA is being replicated in the same direction as the movement of the replication fork. This is the leading strand and is replicated continuously. The other strand of DNA is being replicated in the opposite direction to the movement of the replication fork and thus must be replicated discontinuously. This is the lagging strand. The fragments of newly replicated DNA are joined together by DNA ligase. The formation of the new DNA strands is catalysed by DNA polymerase. This stage is called elongation.
Describe the process of 3’ tailing/polyadenylation of pre-mRNA and it’s purpose
A specific endonuclease cuts the mRNA strand as it’s being transcribed and many RNA nucleotides with A as the nitrogenous base are added. These nucleotides protect against degradation.
Describe the process of 5’ capping and it’s purpose
A nucleotide ‘cap’ is added at the 5’ end of the pre-mRNA molecule by a 5’-5’ linkage. This helps to protect against degradation of the mRNA molecule.
Describe the process of an ELISA. What type of assay is this?
An ELISA is used to determine the concentration of a protein in a sample. The protein (or an antibody specific to the protein) is immobilised on the sides of a well and the antibody (or protein) is added to the well. A second antibody which binds to the protein-antibody complex is then added. This antibody has an enzyme attached. The well is then washed out to remove any unbound antibodies. The substrate for the enzyme on the second antibody is then added and the reaction produces a coloured product. The rate of formation of product, which is proportional to the amount of protein initially present, is measured by a colorimeter. An ELISA is an immunoassay.
Describe the process of carrying out a microarray
Microarrays analyse the expression of thousands of genes simultaneously. They can be used to compare the expression of mRNA from 2 different sources e.g. tumour cell and healthy cell. The 2 DNA samples are each labelled with a different colour eg. red and green. Each dot on the microarray represents a gene, and the proportion of each colour in the dot (which will be some mixture of the two colours) represents the relative expression of that gene by each source.
Describe the process of gel electrophoresis
A technique used to separate DNA fragments on the basis of their size. The apparatus consists of an agarose gel, with wells at one end in which the DNA samples are placed, an anode and cathode at either end of the gel to generate a potential difference (cathode at the end nearest the wells) and a buffer solution on the gel. The DNA fragments are placed in the wells and a potential difference is applied across the gel for a fixed amount of time. The fragments will move towards the anode at the other end of the gel because they are negatively charged due to their phosphate groups. Similar fragments can move through the gel more easily and thus move quicker and further through the gel in the fixed amount of time. At the end of the electrophoresis a stain is added or some form of detection is used so the positions of the fragments can be detected.
Describe the process of PCR
Used to amplify a sample of DNA. The process consists of a 3 stage cycle which is repeated over and over to exponentially increase the amount of sample DNA. You start with a mixture of sample DNA, specific DNA primers, the enzyme Taq polymerase, and free DNA nucleotides. First, the sample is heated to 95C to separate the strands of DNA into single strands. Secondly, the sample is cooled to 55C and the DNA primers bind to their complementary sequences in the sample DNA. Thirdly, the heat is increased to 72C and Taq polymerase catalyses replication of the stretch of DNA between the primers. The amount of the desired stretch of DNA has now doubled, and will double for every repeat of the cycle.
Describe the process of splicing and it’s purpose
Splicing involves the removal of introns, non-coding regions, from the pre-mRNA molecule by endonucleases. Only exons remain, giving an open reading frame to be translated. Introns are not intended to be translated so splicing is necessary to give the correct protein sequence.
Describe ether secondary structure of RNA molecules
RNA strands can form stem-loops, in which complementary base-pairs form between nucleotides, running antiparallel, in the same strand.
Describe the structure of a chromosome (unreplicated)
Each chromosome consists of one DNA molecule complexed with proteins. Histone proteins form octamers and the DNA molecule loops twice around each octamer, forming a structure called a nucleosomes. This ‘beads on a string’ arrangement, with the DNA as the string and the nucleosomes as beads, is then organised into hanging loops attached to a protein scaffold.
Describe the structure of a eukaryotic ribosome. Where in the cell are ribosomes assembled?
A eukaryotic chromosome consists of a 60s subunit and a 40s subunit, making an 80s subunit overall. Ribosomes are made of rRNA and proteins. They are assembled in the nucleus.
Describe the structure of a nucleotide
A nucleotide consists of a pentose sugar (ribose in RNA, deoxyribose in DNA) with a phosphate group attached at carbon-5 and a nitrogenous base at carbon-3. The nitrogenous base may be C, G, A, T or U
Describe the structure of chromatin
In chromatin each DNA molecule is associated with octamers of histones proteins. Each molecule loops around a histone molecule twice forming structures called nucleosomes. This gives rise to a ‘beads on a string’ arrangement with nucleosomes as beads and DNA as the string. In euchromatin, the DNA and nucleosomes remain in the beads on a string arrangement. In heterochromatin the DNA and nucleosomes are further condensed into a solenoid arrangement which is much denser than euchromatin and is not transcribed.
Describe the termination stage of transcription
Transcription stops when a specific DNA sequence is recognised. The product of transcription is pre-mRNA, which must be converted to mature mRNA after transcription.
Describe the termination stage of translation
Translation stops when a stop codon is reached. There is no complementary tRNA molecule for a stop codon, instead a release factor binds and the finished polypeptide and tRNA molecules are released.
Do silent mutations cause disease?
Most don’t, but some can by disrupting splicing.
Explain why the genetic code is degenerate and the significance of this
Some amino acids are coded for by more than one codon. This means a mutation may not necessarily cause a change in amino acid sequence.
Explain why the genetic code is a triplet code.
The genetic code is a triplet code because each amino acid is coded for by a specific set or sets of three bases
Give 2 ethical conundrums of genetic testing
If a patient tests positive for a dominant genetic disease you know that one of their parents must have it - should you then tell them?
If you start genotyping individuals the information could be used by many different people; government, police, insurance companies - is this fair?
Give 2 ethical conundrums of karyotyping an unborn child
Obtaining foetal DNA samples is invasive and can cause miscarriage. Diagnosis of genetic disease in an unborn child could cause the parents to decide to terminate the pregnancy.
Give 2 examples of proteins secreted by each of the secretory pathways
Constitutive: albumin, collagen.
Regulated: insulin, neurotransmitter
Give 3 mechanisms involved in clot breakdown
Removal of activated factors, proteolytic digestion of fibrin and inhibitor molecules for the enzymes involved.
Give 5 ways in which the blood clotting process is regulated.
1) Most factors are present in inactive zymogen form and in very low concentration so that clotting is not triggered by accident.
2) The cascade mechanism amplifies the original signal
3) Clotting factors are localised at the site of damage because carboxyglutamate binds to damaged tissue
4) Thrombin feeds back and activates factors in the intrinsic pathway
5) Multiple processes terminate clotting including the removal of activated proteins, proteolytic digestion and binding of inhibitors
Give 6 ways in which bacterial protein synthesis is different to protein synthesis in humans
- Simpler ribosomes with smaller subunits
- Only one type of RNA polymerase
- Different transcription/translation factors
- Transcription and translation are coupled (in bacteria)
- Short-lived mRNA with no post-transcriptional processing
- Distinct translation initiation mechanism
Give an example of a disease which results from misfolding of proteins, with brief detail about the misfolding
Alzheimer’s disease. Misfolded proteins arise from beta-sheets in different proteins interacting with each other, giving rise to amyloid plaques. Misfolded proteins stimulate other proteins to misfold.
Give an example of an enzyme regulated by phosphorylation
Insulin or glucagon
Give an example of an enzyme regulated by proteolytic cleavage
Trypsin (from trypsinogen) or pepsin (from pepsinogen)
Give an example of an enzyme that is regulated by allosteric regulation
Phosphofructokinase, activated by AMP and fructose-2,6-bisphosphate, inhibited by ATP, citrate and H+
Give an overview of the secretory pathway
A free ribosome in the cytoplasm begins translating the mRNA molecule for a protein. During translations, a signal sequence is produced (hydrophobic aa sequence). An SRP molecule (signal recognition peptide) recognises the signal sequence and binds to it which halts translation. SRP, bound to GTP, then directs the ribosome to a SRP receptor on the ER membrane. SRP dissociates when the ribosome reaches the SRP receptor, and protein synthesis resumes. The polypeptide is fed into the ER lumen as it is synthesised, through a peptide translocation complex. Once the entire protein has been formed the signal sequence is cleaved by the enzyme signal peptidase. The ribosome dissociates and is recycled.
Give names and descriptions of 3 different structural abnormalities involving interaction between chromosomes
1) Translocation: a part of one chromosome is transferred to another non-homologous chromosome, with no loss of genetic material overall.
2) Reciprocal translocation: two non-homologous chromosomes swap sections of genetic material with no loss of genetic material overall.
3) Robertsonian translocation: the P arms of two acrocentric chromosomes join together to form one super-chromosome
Give names and descriptions of 5 different structural abnormalities within one chromosome
Deletion - loss of genetic information from the chromosome
Duplication - doubling of genetic information in the chromosome
Inversion - genetic information is rearranged within the chromosome with no loss
Ring chromosome - the ends of both arms of the chromosome are lost and it forms a ring structure
Isochromosome - two structures form from one chromosome, one made from the p arms and one made from the q arms
Give the cause, in words and in a karyotype report, of Down’s syndrome
Trisomy 21: 47, XY, +21
Give the cause, in words and in a karyotype report, of Edward’s syndrome
Trisomy 18: 47, XY, +18
Give the cause, in words and in a karyotype report, of Klinefelter syndrome
3 sex chromosomes (two X and one Y): 47, XXY
Give the cause, in words and in a karyotype report, of Patau syndrome
Trisomy 13: 47, XY, +13
Give the cause, in words and in a karyotype report, of triple X syndrome
Three X chromosomes: 47, XXX
Give the cause, in words and in a karyotype report, of Turner syndrome
Only having one sex chromosome (X): 45, X
Give the cause, in words and in a karyotype report, of XXY syndrome
Three sex chromosomes (1 X and 2 Y): 47, XYY
Give the karyotype report for a normal human male and a normal human female.
Male: 46, XY
Female: 46, XX
Give the name of a chemotherapy drug that targets mammalian cell growth and describe it’s action
Methotrexate - an antifolate, it inhibits DHFR, an enzyme which synthesises tetrahydrofolate (needed for DNA synthesis), so methotrexate inhibits cell growth
Give a name of an antibiotic that targets bacterial cell wall synthesis and describe it’s action
Amoxicillin (or penicillin). Amoxicillin inhibits transpeptidase (enzymes which form cross-links in the peptidoglycan cell walls of bacteria). This causes the cell wall to break down and thus the bacteria lyse due to osmotic pressure
Give the name of an antibiotic that targets bacterial transcription and describe it’s action
Rifampicin - binds to and inhibits RNA polymerase
Give the name of an antibiotic that targets bacterial translation and describe it’s action
Chloramphenicol - binds to the 50s subunit of the ribosome and inhibits the peptidyl transferase enzyme
