Adaptation and Selection

Question 1

Describe how a gene that codes for an enzyme can be passed from one species of bacteria to another

Answer 1

• Horizontal (gene) transmittion

- (Gene passed by) conjugation/through pilus

Question 2

Explain how adding antibiotics to food of cattle increases profit

Answer 2

• Kills pathogenic/harmful bacteria/pathogens
• Disease less likely/improves health/animals healthier/reduces the spread of infection
• Faster growth/more productive animals/lower vet’s bills/increased yield

Question 3

Explain why the act of adding antibiotics to food is now banned

Answer 3

• (adding antibiotics) selects in favour of antibiotic reistance/resistant bacteria more likely to survive
• Increase in numbers/higher proportion of resistant bacteria
• May infect humans/may spread resistance to other species/horizontal transfer

Question 4

Describe how protein structure is used to investigate relationships between species

Answer 4

-More closely related species have more similarities in primary structure
-In same protein/named protein
-Amino acid sequence is related to (DNA) base/triplet sequence
OR
-Similar species have similar immune response to a named protein
-More closely related species produce more precipitate/antibody-antigen complexes/agglutination

Question 5

Why are older people more likely to be affected by bacteria?

Answer 5

Immune system is less effective/more likely to have had other infections/been in hospital

Question 6

How have gene transmission and selection increased the difficulty if treating bacterial infections with antibiotics?

Answer 6

-(Antibiotic) resistant gene/allele
-Vertical (gene) transmission
-Resistant bacteria survive and reproduce
-Increase of frequency of resistant gene/allele (in future generations)
-Horizontal gene transmission - of plasmid
- through conjugation/pilus tube
- can occur between bacteria of different
species

Question 7

How does frequent treatment with antibiotics result in resistant strains of bacteria?

Answer 7

• Mutation occurs
• Resistant gene/allele
• Resistant bacteria survive and reproduce
• Vertical gene transmission/horizontal gene transmission/conjugation

Question 8

How can a gene be passed from one species of bacteria to another?

Answer 8

• Horizontal gene transmission
• Via conjugation/pilus
• Plasmid/gene/DNA replicated/copied
• Plasmid transferred

Question 9

How can an absence of fatty acids result in osmotic lysis?

Answer 9

• Cell wall not foormed/production inhibited
• Lower water potential in bacterium
• Water enters and causes lysis/expansion/pressure

Question 10

How do antibiotics prevent growth of bacteria?

Answer 10

• Prevents cell wall formation/causes cell lysis
• Inhibits ribosomes/protein synthesis
• Prevents DNA replication
• Affects function of cell membrane

Question 11

How does resistance occur due to vertical gene transmission?

Answer 11

(Plasmid/genes transmitted through) cell division/reproduction/replication/generations

Question 12

How does inhibition of ribosomes cause death to bacterial cells?

Answer 12

• Prevents protein synthesis

- (so) enzymes not produced

Question 13

State ways to reduce transmission of bacteria in hospitals

Answer 13

• Isolation/quarantine
• Screening/testing (of patients/doctors)
• Sterilisation of wards/equipment/method to improve hygiene