Microbes and disease Qs

Question 1

Give two features which are characteristics of all viruses.

Answer 1

Capsid, nucleic acid, replicates inside host cells, no organelles.

Question 2

Why are larger samples better for estimations?

Answer 2

Lowers sampling errors

Question 3

When counting bacteria with a haemocytometer, why s a higher value achieved than with dilution plating?

Answer 3

Haemocytometry includes dead and viable cells.

Question 4

Explain how antibiotic resistant bacteria strains develop.

Answer 4

Mutation occurs, causing resistance to the antibiotic. This makes the bacterium more likely to survive and reproduce, allowing the gene to be passed on to it’s offspring by vertical gene transmission.

Question 5

Why do individuals infected with the CTFR gene not pass it on to their children?

Answer 5

Not present in the DNA of gametes

Question 6

Why are viruses used for gene transfer?

Answer 6

Specific
Can multiply and infect other cells with gene.
Can make multiple copies of the gene in the host cell.

Question 7

Symptoms of TB

Answer 7

Persistent cough;
Blood-stained mucus/sputum;
Chest pain;
Breathlessness;
Fever;
Night sweats;
Loss of appetite;
Weight loss

Question 8

Why do some people have an increased risk of developing TB symptoms?

Answer 8

Live in overcrowded areas, so inhalation of air droplet more likely.
Have pre-existing immuno-degenerative disease make their immune system weaker, e.g. HIV.

Question 9

Why are larger values better to use on graphs displaying large amounts of data?

Answer 9

Allows comparison and groups together otherwise seemingly small anomalous groups.

Question 10

Risk factors of CHD

Answer 10

Stress, Obesity, diet rich in sat. fats, lack of exercise.

Question 11

What is the problem with drug tests on small sample sizes?

Answer 11

Not representative on entire population, also anomalous results have greater effect on end result.

Question 12

What is a parasite?

Answer 12

Organism which lives on another organism causing detriment in the process.

Question 13

Three conditions needed for hardy-weinberg principle to be applied to a population.

Answer 13

Large population
Random mating
No mutations of the gene occur
No selection - equal chance for allele to be passed on
Isolation of population

Question 14

When analysing data in a table for Hardy-weinberg, how can you tell two characteristics are alleles of different genes?

Answer 14

Add up to more than 1.

Question 15

Why can’t antibiotics be used against viruses?

Answer 15

Different cell wall structure to bacteria
No mRNA translation
No DNA synthesis
No membrane

Question 16

How does smoking increase the risk of developing CHD?

Answer 16

Raises concentration of fibrinogen which increases the viscosity of the blood.
Nicotine causes platelets to stick causing vasoconstriction. Carbon monoxide combines with haemoglobin reducing the amount of oxygen which can be carried to heart muscle tissues.
Causes a decrease in antioxidants in the blood, increasing damage to the artery walls, resulting in blood clots and obstructions to blood flow.

Question 17

How does high blood cholesterol increase the risk of developing CHD?

Answer 17

Saturated fat is associated to cholesterol, which can be deposited in arteries, creating artheromas which can lead to arteriosclerosis. This narrows the lumen of the artery, causing a blood clot to occur, restricting blood flow and oxygen to heart muscle.

Question 18

What is agglutination?

Answer 18

Clumping together of cells with antigen, which is complementary to specific antibodies, causing binding.

Question 19

What is an antigen?

Answer 19

Protein/glycoprotein that initiates antibody production.

Question 20

If a virus shows antigenic variability, why would this cause a vaccine to be ineffective against it.

Answer 20

Antigens on surface change shape, meaning antibody or receptor of memory cell can no longer bind and identify it.

Question 21

Many new vaccines developed to treat HIV have been considered unsafe for use in a mass vaccination programme, suggest why.

Answer 21

Inactive virus may become active and harmful. Non-pathogenic virus may mutate and harm cells. Genetic information may harm cells. People may test HIV+ after vaccine, affecting their life.

Question 22

What causes sickle cell anaemia, and how does it lead to the sickle shape associated?

Answer 22

Substitution mutation results in glutamic acid being replaced by valine in haemoglobin. This causes it to crystallize upon dissociation from oxygen.

Question 23

What occurs to blood flow as a result of sickle cell anaemia?

Answer 23

Normal blood flow impeded as sickle cells block capillaries and small blood vessels.

Question 24

Give a symptom of sickle cell anaemia

Answer 24

Painful stomach
Enlarging of the heart
Kidney damage
Poor growth and development

Question 25

Why can the X and Y chromosome not form a bivalent?

Answer 25

They are different sizes, so chromatids are unable to line up.

Question 26

How do antibodies protect the body from infection?

Answer 26

Agglutination of antigens
Two antigen binding sites
Clumps of cells destroyed
Precipitation of soluble toxins
Precipitate toxins are neutralised
Stimulate phagocytosis
Label foreign cells for destruction.