Your Answer : (Not Answered)

Correct Answer : B

Correct answer: About one in five

The case fatality rate for V. vulnificus septicaemia is around twenty per cent, and higher still in those with liver disease. Death can follow within a day or two of onset, so treatment depends on recognising the infection early in someone who has recently eaten raw shellfish.

Your Answer : (Not Answered)

Correct Answer : D

Grapes supply fermentable sugar directly, whereas barley stores carbohydrate as starch that yeast cannot use, so malting and mashing exist entirely to convert it. This extra enzymatic stage is the essential difference between the two processes.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: shred solids rather than remove them

A comminutor cuts rags and large solids small enough to pass through the works without blocking pumps, and everything continues down the line. That is its distinction from a screen, which lifts the material out for disposal - and it is why screens are now generally preferred, the shredded material otherwise reappearing in the sludge.

Your Answer : (Not Answered)

Correct Answer : C

Beyond secondary treatment, further steps take out nitrogen, phosphorus, residual solids and specific chemicals, using filtration, chemical precipitation or biological nutrient removal. It is applied where the receiving water is particularly sensitive.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: Growth in size before dividing

Viruses do not grow and divide. They are assembled from separately synthesised components, so a cell yields hundreds of complete particles at once rather than a parent particle enlarging and splitting. The other three are all defining properties: a protein coat, a nucleic acid genome, and replication only inside a host cell.

Your Answer : (Not Answered)

Correct Answer : D

The enzyme copies the retroviral RNA genome into a complementary DNA strand and then into double-stranded DNA, reversing the usual direction of information flow. That DNA is carried into the nucleus and integrated into the host genome by viral proteins.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: Burkitt lymphoma

Burkitt lymphoma is associated with Epstein-Barr virus and, in the endemic form, with malaria, and has nothing to do with H. pylori. The other three are all established consequences of the infection: peptic ulceration, gastric carcinoma, and gastric MALT lymphoma, which frequently regresses when the organism is eradicated.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: TPHA

The Treponema pallidum haemagglutination assay uses treponemal antigen itself, so it detects antibody directed against the organism and is a specific test. VDRL and Kahn’s test are non-treponemal, using the cardiolipin-lecithin-cholesterol antigen; they are excellent for screening and for following the response to treatment because the titre falls, but they give biological false positives in pregnancy, autoimmune disease and several infections, and need a specific test such as TPHA or FTA-ABS to confirm. The Widal test is for enteric fever and has nothing to do with syphilis.

Your Answer : (Not Answered)

Correct Answer : A

Correct answer: A

S. pyogenes carries the group A cell wall carbohydrate, which is what the Lancefield grouping detects and what gives it its everyday name of group A streptococcus. Group B is S. agalactiae, the neonatal pathogen, and group D covers the enterococci and S. bovis.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: All of these

The non-suppurative sequelae are the late, immunologically mediated consequences that follow after the infection itself has resolved and no organisms remain at the site. Acute rheumatic fever follows pharyngitis, acute glomerulonephritis follows either pharyngitis or skin infection, and erythema nodosum is a recognised reactive complication. All three are distinct from the suppurative spread of the organism itself.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: they mediate allergic reaction

Immediate allergic reactions are mediated by IgE, not IgM. The other three statements are all true of IgM: it is the most efficient complement fixer because its pentameric form presents several Fc regions together, it appears as a monomer on the B-cell surface as part of the antigen receptor, and it dominates the primary response before class switching occurs.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: all of these

ELISA is a general method - an antibody or antigen fixed to a plate, and an enzyme-linked partner whose colour change reports binding - so a kit can be built for almost any target. Commercial kits exist for rotavirus antigen in stool, for hepatitis B surface antigen, and for anti-HIV antibodies, the last being the standard screening test.

Your Answer : (Not Answered)

Correct Answer : A

Correct answer: humoral antibody

Congenital agammaglobulinaemia - Bruton’s disease - is a failure of B cells to mature, so almost no immunoglobulin is made. The defect is therefore in the humoral (antibody) arm. Cell-mediated immunity is intact, which is why such patients handle viruses reasonably well but suffer repeated bacterial infections, the very ones antibody normally controls.

Your Answer : (Not Answered)

Correct Answer : A

Correct answer: Physical barrier

These are all physical (anatomical) barriers: they block or sweep away invaders mechanically. Skin is a tough keratinised sheet, hair and eyelashes catch particles, cilia in the airways drive trapped material upwards, and the linings of the gut and respiratory tract present a continuous covered surface. They are the first line of defence and belong to innate immunity.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: Small, circular DNA molecules that can exist independently of chromosomes commonly found in bacteria

A plasmid is a small, usually circular DNA molecule that replicates independently of the bacterial chromosome. It has its own origin of replication, so it is a replicon in its own right, and it carries accessory genes that are useful in some environments but not required for growth.

A protoplast is a cell stripped of its wall, and the membrane structure covering the bacterial chromosome describes the nucleoid or the mesosome rather than a plasmid. The defining features to remember are independent replication and dispensability.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: Haemophilus influenzae

Haemophilus influenzae was the first free-living organism to have its complete genome sequenced, published by Venter and Smith in 1995. It demonstrated the whole-genome shotgun method, which was later applied to the human genome. E. coli followed in 1997 and B. subtilis the same year.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: regulates many genes under varying environmental conditions

A global regulatory system - a regulon or stimulon - controls many genes at once in response to a single condition: heat shock, starvation, oxygen. Coordinating a whole set of responses through one signal is far more efficient than regulating each gene separately.

Your Answer : (Not Answered)

Correct Answer : D

Correct answer: both (a) and (b)

Primase (the DnaG protein) makes the primers at the fork, once on the leading strand and once for each Okazaki fragment. RNA polymerase also has a part at initiation: its transcription across the origin region helps open the duplex, and in some replicons it makes the primer itself. So both enzymes are involved in generating the RNA that starts replication.

Your Answer : (Not Answered)

Correct Answer : C

Correct answer: DNA through RNA to proteins

This is the central dogma: DNA is transcribed to RNA and RNA translated to protein. Retroviruses reverse the first step with reverse transcriptase, but no mechanism translates protein back into nucleic acid, and it is that last impossibility which gives the dogma its force.

Your Answer : (Not Answered)

Correct Answer : A

Correct answer: pathogenic properties

A pathogen in a mixed culture can be selected by what it does to a host - inoculating a susceptible animal, from which the organism can then be recovered in pure culture while the harmless ones are eliminated. It is selection by biological property rather than by nutrient or condition.