article questions Flashcards
Explain what is meant by a stem cell (3)
- a cell that is undifferentiated
- can give rise to specialised cells
- can divide to produce more stem cells
Explain how stem cells become specialised (4)
- stimulus (chemical or hormone)
- activation of some genes
- activated genes are transcribed
- mRNA translated on ribosomes
- proteins are made
- determines cell structure
- cell differentiates
Define species (1)
group of organisms that can interbreed to produce fertile offspring
Explain the process of inflammation (4)
- immune system cells recognise foreign antigens
- mast cells release histamine which triggers inflammation
- histamine causes vasodilation
- increases blood flow to the site
- permeability of blood vessels increase
- cytokines attract white blood cells
Explain why frequency of allele may change from one generation to the next
- random mutation
- natural selection
- immigration / emigration
- genetic drift
Explain how epigenetic events might be involved in causing cancer
- exposure to carcinogen may result in epigenetic changes
- changes in methylation of DNA / modification of histomes
- tumour suppressing gene is less likely to expressed
Describe the stages of clinical trials
- small group of healthy volunteers given the same treatment to test for side effects
- healthy volunteers tested for presence of antibodies to the virus
- group of people risk of contracting given the vaccine
- number of people who developed the viral disease are monitored
Why are contemporary drug testing protocols an improvement on the trial used by William Withering
- safer: pre-testing on animals/cells before testing on humans
- regulated by legislation
- more valid: placebo used as a comparison
- modern day testing involves double-blind trials
- more reliable: more people are tested
- results are analysed statistically
Evaluate whether mutations are always harmful (6)
- genetic code is degenerate (amino acids code by more than one base triplet
- mutation such as substitution can code for the same amino acid
- evolution
- explain example in text
- mutation such as deletion can shift reading frame
- significant change in primary structure thus change in 3D shape
- results in non-functional protein
Explain why a gene mutation can results in an enzyme that is unable to break down lipids
- gene is a sequence of bases on a DNA molecule that codes for the amino acid sequence in a protein
- if a mutation occurs to a gene there is a change in sequence of bases of a gene
- changes the primary structure of the enzyme
- different R groups, different types of bonds formed in tertiary structure
- changes the folding of tertiary structure
- changes the shape of active site of enzyme
- lipid no longer fits into the active site
Explain why doctors have been advised to limit the prescription of antibiotics
- some bacteria are resistant to antibiotics
- bacteria survives and reproduce even if antibiotics are used
- antibiotic no longer effective
Explain how mutations occur
- mutations are changes of base sequences of DNA caused by errors in DNA replication
- (substitution, deletion, insertion, duplication, inversion)
- mutagens cause genetic mutation (Eg: smoking)
Describe and explain natural selection in regard to antibiotic resistance
- antibiotic acts as the selective pressure
- some bacteria is resistant to antibiotics
- resistant bacteria survive and reproduce
- pass on resistance gene
- antibiotic is no longer effective
- infections cannot be treated with antibiotics anymore
Give two ethical arguments to support the use of rats and mice with spinal cord injuries in these experiments
- need to carry out experiments on animals with well developed CNS
- spinal cord injuries are difficult to treat
Describe how antigens are presented to immune cells
- macrophages engulf antigens
- antigen is presented on the surface of antigen presenting cells
- CD4 receptors that are complementary to antigens bind to antigen presenting cells
