exam improvement bio

Why is ethanol added when extracting DNA from a fruit?

To precipitate the DNA

Differences between product of meiosis and mitosis…

• mitosis - 2 cells, genetically identical, body cells, diploid

• meiosis - 4 cells, genetically different, sex cells, haploid

Vaccine working:

• they are immune to (disease)

• because the vaccination contained an antigen / bacteria have antigens

• memory lymphocytes

• leading to the production of antibodies

• leading to a secondary (immune) response

memory lymphocytes

are a type of white blood cell, which forms a crucial part of the body’s immune system. Their key function is to remember specific pathogens, for example bacteria or viruses, that the body has encountered before.

why do bacteria become resistant to medicinal drugs

• people do not finish their course (of the drug) / overuse / repeated exposure to antibiotic.

• natural selection occurs / evolution

• some bacteria have a mutation / genetic variation

• these resistant bacteria survive / resistant bacteria reproduce

why was the three domain system introduced?

• improved genetic analysis

• DNA/RNA (screening/sequencing)

• Domain theory is based on genetics

• differences between coding and non-coding DNA

enzymes don’t forget

• increased chance of collision

• substrate complexes formed

why do people no get vaccinated

• concerns over side effects of immunisation / concerns over the risk of allergic reactions

• medical reason for not being immunised

• too young for vaccination programme

• no access to healthcare

how does the lens refract the light more?

• by becoming thicker

functions of reflex arc:

• rapid response

• protect the body in response to danger

• involuntary automatic response

advantages and disadvantages of vaccination

herd immunity

• If a large number of the population are vaccinated, it is unlikely that an unvaccinated individual will become infected with the pathogen