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1
Q

Explain the meaning of the term stem cell. (2 Marks)

A
  • undifferentiated cell
  • that can give rise to other types of cell
  • no limit to division
  • correct reference to totipotent / pluripotent
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2
Q

Q: Human bone marrow contains stem cells that can give rise to various types of blood cell including white blood cells. Suggest how a stem cell in the bone marrow can become a differentiated blood cell. (4 Marks)

A
  • stimulus e.g. chemical
  • (causes) some genes active / some inactive (in bone marrow stem cell)
  • only the active genes are transcribed
  • (because) mRNA made (only at active genes)
  • protein made
  • which (determine) cell structure / function / permanently modifies cell
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3
Q

State three potential sources of human stem cells. (3 Marks)

A
  • cord blood /umbilical cord / placenta
  • fertilized egg / zygote / blastocyst / (early) embryo
  • site within blastocyst
  • bone marrow
  • brain / connective / skin / liver cells
  • addition of adult nucleus to enucleated egg cell
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4
Q

What is in vitro and in vivo? (2 Marks)

A
  • In vitro - the technique of performing a given procedure in a controlled environment outside of a living organism.
  • In vivo - experiment on a living subject.
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5
Q

Explain how the new cells become specialized and develop into neurons in the brain (4 Marks).

A
  • genes (in the new cells) are activated / transcribed
  • detail of transcription
  • detail of translation
  • proteins determine function / structure of cells
  • cell processes form
  • the new neurons are relay neurons
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6
Q

Explain how differential gene expression can enable cells which have the same genetic material to have very different structures and functions, and thus develop into different tissues/organs. (3 Marks)

A
  • different genes active in different cells / different genes active at different times / some genes active / inactive
  • active genes make mRNA
  • active genes make proteins / polypeptides
  • (proteins) control cell processes
  • permanent change (to cell)
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7
Q

Ethic issues of using embryonic stem cells? Discuss how regulatory authorities control the use of embryonic stem cells in research. (3 marks)

A
  • Monitoring research / ensuring research is necessary
  • Issue licences for stem cell research
  • Monitoring sources of stem cells
  • Ensure that only early stage embryos are used as sources of stem cells
  • Prevention of unethical use of stem cells
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8
Q

Suggest two reasons why there are regulating authorities for human embryo research. (2 Marks)

A
  • decide on max age of embryo allowed for research
  • setting or considering ethical / legal aspects / judging what is acceptable / follow a code
    of practice
  • example of what is / is not acceptable
  • checking that source of stem cells is acceptable
  • stopping of cloning (of humans)
  • appropriate reference to unnecessary repeating of research
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9
Q

Suggest why these regulating authorities should include people involved in human embryo research and people not involved in embryo research. (4 Marks)

A

People involved in embryo research
- being able to (fully) understand the science / recognize what is possible benefits / risks / judge in an informed manner
People not involved in embryo research
- giving a balanced /alternative / wider / named view

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10
Q

Q: State three differences between a group of embryonic stem cells and the cells in a tissue. (3 marks)

A
  • Embryonic stem cells are totipotent / pluripotent and cells of a tissue are not
  • Embryonic stem cells are undifferentiated / unspecialised and cells of a tissue are
    differentiated / specialised
  • Cells of a tissue work together for a particular function and stem cells do not
  • Stem cells are capable of continuous division / have no Hayflick limit and cells of a tissue
    are not
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11
Q

State the levels of organization: (1 Mark)

A
  • Cell, tissue, organ, organ system, organism
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12
Q

Give one difference between an organ and a tissue. (2 Marks)

A
  • Organ has many functions; tissue has one fewer

- Organ has many/several cell types/tissues; tissue has one/fewer

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13
Q

Suggest one way in which tissues and organs are similar. (1 Mark)

A
  • Both have cells working together/for the same function
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14
Q

Describe how a fertilized egg can be used as a source of human pluripotent stem cells. (3 Marks)

A
  • Fertilized egg allowed to grow for a few days/divide several times
  • Blastocyst/hollow ball of cells created
  • Cells in inner cell mass are pluripotent. Cells are harvested by special procedure
  • Source of fertilized egg e.g. spare embryo after IVF
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15
Q

Q: How are cells organized into tissues? (2 Marks)

A
  • Specialized cells group into clusters
  • Cells bind to each other, due to specific recognition proteins (adhesion molecules). These
    extents out of the protein and they bind to other adhesion molecules on other cells (the molecules must be complementary in order to bind – thus these recognition proteins determine which cell can or cannot attach)
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16
Q

Suggest why stem cells can be used to reverse this paralysis. (2 Marks)

A
  • stem cells being totipotent / pluripotent
  • can specialize or differentiate / can give rise to differentiated / specialized cells
  • these can replace damaged cells (in spinal cord of Dachshund) / new nervous tissue can
    be formed
  • capable of continuous division / no Hayflick limit
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17
Q

Q: Suggest why, after testing a drug on tissue samples, the drug is also tested on whole animals. (3 Marks)

A
  • the drug may have an effect on other tissues
  • needing to find out effects on organs / systems / whole organism
  • drug metabolism
  • finding out whether drug is safe / toxic
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18
Q

Q: Explain why animals had to be used to test for example a vaccine. (2 Marks)

A
  • need to use living nerve tissue

- vaccine contains live virus / virus may revert to virulence / virus causes disease in humans

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19
Q

Suggest one ethical issue in the use of chicken embryos in this investigation. (1 Mark)

A
  • chicken (embryo) is a vertebrate / feels pain / will die / cannot give consent/
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20
Q

Q: Suggest the advantages of using mice as a “knock out” model in research compared with the use of humans. (2 Marks)

A
  • control genetic make-up / these mice are homogeneous / humans have genetic variety
  • this allows (one) gene function to be investigated
  • drugs can be used which cannot be used / are unethical for use with humans /
  • larger sample size can be used
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21
Q

Name one non-animal alternative that can be used in research and give an advantage of this alternative method. (2 Marks)

A
  • tissue culture / computer modelling / use of humans / population studies
  • reduce use of animals / no animals harmed / more ethical
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22
Q

: Explain why new medicines are tested on animals before they are tested on humans. (2 Marks)

A
  • need to find out if the drug works / efficacy
  • need to find out if the drug is safe / toxic / has side effects
  • need to find the correct dose
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23
Q

Give one reason why some people believe that it is ethically unacceptable to use animals in medical research. (1 Mark)

A
  • will feel pain / cruel / animals have rights / not given their consent / causes damage / harm / blindness / stress
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24
Q

Why not carry out experiments on humans? (2 Marks)

A
  • Unethical

- More complex organisms

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25
Q

During the G1 phase of the cell cycle, some cells of the embryo become specialized. Describe the processes which cause a cell to become specialized. (4 Marks)

A
  • correct stimulus e.g. chemical
  • (stimulus) activates some genes / inactivates genes
  • transcription / mRNA produced at active genes
  • translation of mRNA produces protein /polypeptide
  • this protein either permanently modifies cell or determines cell structure / function
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26
Q

Explain how molecular phylogeny could be used to determine the relationships between the different animal species? (2 Marks)

A
  • (compare) sequences of bases in DNA /amino acids in proteins
  • the more similarities in common the more closely-related the subspecies
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27
Q

Investigators used the polymerase chain reaction (PCR) to increase the quantity of DNA from samples. Describe how one PCR cycle would increase the quantity of DNA present. (4 Marks)

A
  • heat to 90-98◦C to break hydrogen bonds between (DNA) strands / separate the strands of DNA
  • joining of primers / annealing at 50-75◦C
  • elongating / extension / addition of nucleotides / DNA polymerase involved in formation
    of phosphodiester bonds
  • to double the quantity (of the DNA)
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28
Q

Explain how gel electrophoresis could be used to find out from which animal species the DNA comes from. (5 Marks)

A
  • loading of electrophoresis tank
  • current / potential difference applied across the gel
  • use gene probe / DNA stain
  • use of STRs / DNA of black panther
  • compare bands / DNA profiles
  • a match would indicate that (DNA from) a black panther was present
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29
Q

Explain how the results of DNA profiling of tissue samples from the different species could be used to provide evidence that they share common ancestry. (3 Marks)

A
  • reference to bands produced
  • reference to bands at certain positions
  • common bands contain similar DNA fragments
  • the more similar the patterns the closer the relationship / more likely to have recent
    common ancestor
  • very few differences if still a sub-species
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30
Q

Q: Suggest how natural selection could have given rise to different adaptations shown within each different animal species. (5 Marks)

A
  • idea of selection pressure / change in environment
  • competition / predation
  • Mutation occurs in the population
  • idea of advantageous allele
  • idea that individuals with advantageous alleles / characteristics survive and breed
  • idea of (advantageous) allele / mutation being passed on (to future generations)
  • increased frequency of advantageous alleles in the population
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31
Q

Q: What does polygenic mean? (2 Marks)

A
  • A trait controlled by two or more genes

- at different loci on different chromosomes.

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32
Q

Define phenotype. (1 Mark)

A
  • appearance of an organism due to the contribution of the genotype and environmental factors.
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33
Q

What does buffer means? (1 Mark)

A
  • A buffer is a chemical substance that helps maintain a relatively constant pH in a solution, even in the face of addition of acids or bases.
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34
Q

Q: Why are biological systems buffered? (2 Marks)

A
  • Buffering is important in living systems
  • To maintain a fairly constant internal environment,
  • also known as homeostasis
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35
Q

Q: What are biological buffers? (2 Marks)

A
  • molecules that donate or accept protons

- to resist changes in pH as acids or bases are added to the solution.

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36
Q

Q: Explain what is meant by the term gene mutation. (2 Mark)

A
  • change in DNA

- change / deletion / addition / duplication / substitution of bases / nucleotides

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37
Q

Q: Describe how a frameshift mutation could result in the production of a protein with a variety of shorter primary structures. (3 Marks)

A
  • (adding or removing one or two nucleotides) changes the triplet code
  • introducing a new start / stop codon
  • coding for a shorter sequence of amino acids
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38
Q

Q: Explain how a single base mutation can lead to an altered primary structure of an enzyme. (3 Marks)

A
  • changing a base results in a change in the triplet code
  • this changes the codon(s) in the mRNA
  • resulting in a different amino acid / amino acid sequence (in the primary structure)
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39
Q

Q: Explain what is meant by the term totipotent stem cell. (2 Marks)

A
  • totipotent (stem cells) can give rise to all / any / 216 cell types
  • (stem cells) are undifferentiated / unspecialized
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40
Q

Q: Suggest why injecting totipotent stem cells may benefit a person with a shortage of white blood cells. (1 Mark)

A
  • they can give rise to white blood cells
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41
Q

Q: Suggest one risk to the person receiving the stem cells. (1 Mark)

A
  • possible route to infection / rejection by recipient
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42
Q

Q: Cells stop dividing as they become specialized. Describe the processes that take place inside a cell during specialization. (4 Marks)

A
  • genes would be activated / deactivated
  • active genes transcribed / mRNA produced
  • translation (of mRNA) to produce proteins
  • idea that proteins modify cell / determine function of cell / structure of cell altered
    permanently
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43
Q

Q: Specialized cells of an embryo become tissues and organs in the fetus. Give two differences between tissues and organs. (2 Marks)

A
  • tissues made of cells and organs made of tissues
  • tissues made of one type / similar types of cells AND organs made of different tissues
  • organs have more functions than tissues
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44
Q

Q: Describe therapeutic cloning. (4 Marks)

A
  • Take a cell from the patient (diploid)
  • The nucleus of this cell fuses with an enucleated ovum (i.e. its haploid nucleus has been
    removed) - this is known as somatic cell nuclear transfer
  • This new cell is now a diploid (like a zygote)
  • Cell is then stimulated to undergo mitosis
  • At the blastocyst stage, stem cells are isolated and encouraged to develop into tissues.
  • This result in cell lines and eventually in organs for transplantation
  • Somatic cell nuclear transfer is used to produce blastocysts from which human stem cells
    are extracted.
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45
Q

Q: What is the difference between differentiation and development? (3 Marks)

A
  • Cellular differentiation is the process where a cell changes from one cell type to another.
  • the cell changes to a more specialized type.
  • occurs numerous times during the development of a multicellular organism
  • as it changes from a simple zygote to a complex system of tissues and cell types.
  • Development is the process of growth
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46
Q

Q: Explain how cells produced from stem cells can have the same genes yet be of different types. (3 Marks)

A
  • {Not all / different} genes are switched {on / off} /active / activated;
  • Correct and appropriate reference to factors /mechanisms for gene switching;
  • E.g. reference to promoters / transcription factors;
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47
Q

Q: State three differences between a group of embryonic stem cells and the cells in a tissue. (3 Marks)

A
  • embryonic stem cells are totipotent / pluripotent and cells of a tissue are not embryonic stem cells are undifferentiated / unspecialized and cells of a tissue are differentiated / specialized
  • cells of a tissue work together for a particular function and stem cells do not
  • stem cells are capable of continuous division / have no Hayflick limit and cells of a tissue
    are not
48
Q

Q: There are ethical concerns in the use of embryonic stem cells. Suggest alternatives. (3 Marks)

A
  • Use adult stem cells (brain/connective /skin/ liver cells)
     Thus no problem with immune rejection
     No ethical concerns
  • Use of reprogrammed somatic cells
     Known as induced pluripotent stem cells (iPSCs)
     This resemble human embryonic stem cells
49
Q

Explain what is meant by the term pluripotent. (2 Marks)

A
  • cells can divide
  • these cells are undifferentiated / unspecialized / these cells can undergo differentiation /
    specialization
  • they give rise to most cell types / all cell types except extra-embryonic tissues
50
Q

Suggest how organs develop from pluripotent cells. (2 Marks)

A
  • pluripotent stem cells giving rise to tissues

- (organs) made up of groups of / several / different tissues

51
Q

Cells taken from the inner cell mass of a blastocyst are (1 Mark)

A

pluripotent and can only form embryonic cell types

52
Q

Describe the differences between a totipotent stem cell and a pluripotent stem cell. (2 Marks)

A
  • totipotent cells can give rise to / differentiate to become any cell / extra embryonic tissues
  • pluripotent cannot give rise to / differentiate to become all cells in the body / extra
    embryonic tissues
  • only totipotent cells can give rise to other totipotent cells
  • totipotent cells can give rise to an entire human being, pluripotent cells cannot
53
Q

: What does cell culture mean? (2 Mark)

A
  • is the process by which cells are grown under controlled conditions,
  • generally, outside their natural environment.
54
Q

How is gene expression related to cell differentiation? (4 Marks)

A
  • Gene expression is the specific combination of genes
  • that are turned on or off (expressed or repressed),
  • and determines cell functions
  • Cell differentiation is how embryonic cells become specialized cells
55
Q

Describe the properties of stem cells that enable them to repair damaged tissues. (2 Marks)

A

stem cells being totipotent / pluripotent

  • can specialize or differentiate / can give rise to differentiated / specialized cells
  • these can replace damaged cells / form new tissue (in knee joint)
  • capable of continuous division / no Hayflick limit
56
Q

Describe the risks that may arise from the use of stem cells donated by other adults. (2 Marks)

A
  • risk of rejection
  • risks when taking immunosuppressant drugs
  • risk of transmission of disease
  • may cause cancer to develop
57
Q

Q: What is a tissue culture? (3 Marks)

A
  • the growth of cells
  • in an artificial medium
  • derived from living tissue
58
Q

Fibrous tissues are made from fibrous proteins. Describe the structure and properties of fibrous proteins. (4 Marks)

A
  • Idea of little tertiary / quaternary structure or mainly secondary structure
  • Made up for long / linear / straight molecules / (poly) peptides / polymers (NOT: peptide
    bonds)
  • Idea of cross-linking (between one polypeptide chain and another)
  • Idea of repeating amino acid sequences
  • Insoluble (ignore: hydrophobic on outside)
  • Tough / strong
59
Q

Q: Argue in the use of embryonic stem cells over animal trial.

A
  • Use of stem cells can help us to use fewer animals
  • More cost-effective than using animal models
  • An embryonic stem cell is capable of growing and differentiating into a wide variety of
    different cell types, which can ultimately grow into a human organ.
  • In vitro human tissue from stem cells, have better ability to assess the toxicity of a
    substance,
  • obtain a human profile rather than an animal one for the drug
  • genetic engineering embryonic stem cells, can coaxed cells to develop into diseased
    human tissues. Then, these tissues can be utilized for drug screening.
  • Less time consuming
  • testing relates to ethnic diversity. Animal models don’t have the ethnic diversity of
    humans.
60
Q

Describe the processes involved in the production of the mRNA that codes for a protein. (6 Marks)

A
  • reference to transcription
  • DNA unwinding / unzipping in the region of the gene coding for lysozyme
  • (RNA) (mono)nucleotides line up against / attach to complementary bases (on the DNA)
  • on the template / antisense strand
  • formation of phosphodiester bonds (between adjacent mononucleotides)
  • reference to post transcriptional modification/ RNA splicing
  • spliceosome
  • details of post transcriptional modification
61
Q

Describe the structure of proteins. (4 Marks)

A
  • reference to consisting of amino acid
  • (amino acids) joined by peptide bonds
  • folding into two / three dimensional shape
  • held together by ionic bonds / hydrogen bonds / disulfide bridges
  • between the R groups
  • description of globular / fibrous proteins
62
Q

Describe the process of protein synthesis that occurs in the cytoplasm. (5 Marks)

A
  • Ribosome attaches to mRNA
  • tRNA carries an amino acid
  • anticodon-codon interaction/complementary base pairing between tRNA and mRNA
  • formation of hydrogen bonds between the tRNA and mRNA
  • peptide bond between amino acids
  • peptide bond formed by a condensation reaction
  • tRNA released from mRNA/ribosome
  • ribosome attaches to / detaches from sequence on mRNA
63
Q

Proteins are made up of amino acids. Describe how amino acids join together to form the three- dimensional structure of a protein. (5 Marks)

A
  • Reference to peptide bonds joining amino acids
  • Between amino group of one amino acid and carboxyl group of another
  • The sequence of amino acids is the primary structure of the protein
  • Reference to folding of primary structure held together by bonds
  • Disulfide bridges / hydrogen bonds/ ionic bonds / van den Waals forces
64
Q

Q: Describe the three-dimensional (tertiary) structure of an enzyme. (3 marks)

A
  • Globular
  • The active site has a specific shape
  • Bonds are formed between R groups
  • Such as disulphide bond, hydrogen bonds, hydrophobic interactions (between R groups)
65
Q

Name the type of cell division by which a stem cell can give rise to many genetically identical cells. (1 Mark)

A

Mitosis

66
Q

Suggest why it might be useful to keep a supply of live stem cells from your brain in a laboratory. (2 Marks)

A
  • if you (suffered an accident / disease / deterioration) and needed to replace damaged brain cells;
  • would be genetically the same as the rest of your cells;
  • able to replace more than one kind of brain cell;
  • goes on generating new cells as required
67
Q

Suggest why research with embryonic stem cells is further advanced than research with adult stem cells. (2 Marks)

A
  • embryonic cells are easier to work with than adult stem cells;
  • embryonic cells are (relatively) undifferentiated whereas adult stem cells {are/appear to
    be} less so;
  • embryonic stem cells are {totipotent / pluripotent /able to become any kind of cell in the
    body}, but adult stem cells are {multipotent / able to become only a limited number of
    cell types};
  • embryonic stem cells have a wider range of clinical applications / adult stem cells have a
    narrower range of clinical applications
68
Q

Explain how stem cells become specialized and develop into heart muscle cells. (4 Marks)

A
  • appropriate stimulus e.g. chemical, hormone
  • activation of some genes
  • only the activated genes are transcribed / mRNA made only at active genes
  • mRNA translated (on ribosomes)
  • protein made
  • which determines / eq cell structure / function / permanently modifies cell reference to
    cell differentiation
69
Q

Explain the advantages of using stem cells from the patient instead of using stem cells from a donor. (2 Marks)

A
  • genetically identical cells (to patient)
  • no risk of rejection
  • no need to take immunosuppressant drugs
  • less risk of infection
70
Q

Explain why chemicals from a whole heart are needed to produce mature heart cells from immature heart cells. (4 Marks)

A
  • chemicals switch on some genes
  • differential gene expression
  • genes coding for heart cell structures / functions are active / switched on
  • transcription / mRNA produced at active genes
  • mRNA is translated / used to produce proteins
  • these proteins determine the structure / function of mature heart cells
71
Q

Describe contemporary drug testing protocols that could be used to test drugs developed for treating heart disease. (3 Marks)

A
  • (phase I) drug tested on (small number of) healthy people / volunteers
  • (phase II) drug tested on small number of patients (with heart disease)
  • (phase III) drug tested on large number of patients (with heart disease)
  • reference to placebo / double blind trial (during phase II / phase III)
72
Q

Arguments in favour of using stem cells to treat cancer

A
  • Relief of human suffering;
  • Cancer a very serious condition / causes death / severe distress / no satisfactory
    alternative way of treating it;
  • Debatable whether an embryonic stem ccli can be regarded as a potential human life but adult stem cells are not a potential human life;
  • Developing stem cell technology could lead to cures for other conditions;
  • Any balanced view on the use of stem cells
73
Q

Arguments against using stem cells to treat cancer

A
  • Stem cells can be harvested from human embryos /increases pressure to produce embryos specially for treating people;
  • Embryos have right to life / use at embryos = murder;
  • Research using non-embryonic stems could make use of embryonic stem cells
    unnecessary;
  • Could be unforeseen side effects for the woman / any children she has / correct reference to gene line / might lead to even more ethically questionable practices;
74
Q

Suggest how a vaccine against the Zika virus would work. (6 Marks)

A
  • that vaccine / antigens / attenuated virus needs to be injected into person
  • to stimulate the (primary) immune response
  • macrophages present the antigen (in the vaccine) to T helper cells
  • T helper cells release cytokines to stimulate B cells / T killer cells
  • resulting in formation of memory (T / B) cells
  • memory cells remain in the body
  • these memory cells are activated on infection (with the virus)
  • the resulting immune response will be faster
75
Q

the immunity that individuals given this vaccine would develop

A

artificial active

76
Q

Describe the tests that would need to be carried out before the Zika vaccine could be used to prevent birth defects caused by this virus. (3 Marks)

A
  • tested on animals
  • tested on (small number of) healthy individuals
  • tested on small number of people who are likely to come in contact with Zika
  • (then) testing on a small number of pregnant women (to check for side effects in the baby)
  • it is unlikely that phase III will be carried out first
77
Q

Explain how scientists have shown that the Zika virus in Brazil is more closely related to the Asian strain. (3 Marks)

A
  • analyzing the structure of RNA / protein / genetic material from all three viruses to determine the sequence of bases in the RNA / amino acids in the protein
  • reference to use of phylogenics
  • use of gel electrophoresis to analyze RNA / proteins of the three viruses
  • closely-related viruses will have similar protein / RNA
78
Q

Q: Describe the structure of a virus. (2 Marks)

A
  • reference to nucleic acid / RNA or DNA
  • a protein coat / capsids
  • envelope may be present
  • enzymes may be present
  • receptors / attachment molecules (on surface)
79
Q

Suggest why antibiotics cannot be used to treat infections caused by viruses. (1 Mark)

A
  • are non-living
80
Q

Q: State two ways that hospitals can reduce the spread of infections caused by viruses. (2 Marks)

A
  • use of hand washes
  • reduce proximity of patients to each other / isolation
  • suitable dress eg masks, no jewellery
  • suitable washing of bedding / cutlery / cups
  • correct disposal of dressings / needles
  • screening of patients / visitors
  • sterilizing equipment / disinfecting surfaces
81
Q

: Describe the role of T killer cells in the immune response to a viral infection. (4 Marks)

A
  • destruction of (virus-)infected (host) cells
  • by chemicals/ enzymes / perforins (released from T killer cells)
  • virus / adenovirus are released (from cells)
  • antibodies can now bind to (virus / adenovirus)
  • the virus can now be phagocytosed (by macrophages) / destroyed by macrophages
  • memory (T killer) cells form for secondary immune response
82
Q

Suggest three potential risks to the health of a person with Alzheimer’s disease of this treatment. (3 Marks)

A
  • risk of infection / disease / pathogens from the donor
  • risk of infection from contaminated equipment during the procedure
  • risk of cancer / abnormal growth
  • rejection
  • increased susceptibility to infections due to immunosuppressant drugs
83
Q

State how the genetic material in a retrovirus differs from the genetic material in a bacterium. (2 Marks)

A
  • RNA in HIV and DNA in bacterium
  • comparative description of nucleic acid e.g. circular in bacterium and linear in HIV
  • plasmids in bacterium and no plasmids in HIV
84
Q

Why use patients own stem cells? (1 Mark)

A
  • To avoid transplant rejection

- Easier/faster way to find cells

85
Q

What are immunosuppressant drugs used for? (1 Mark)

A
  • make the body less likely to reject a transplanted organ
86
Q

As part of the immune response, a B cell has to be activated. It then divides to form a clone of cells. These cells then differentiate into plasma cells, which produce antibodies. Describe how a B cell is activated. (3marks)

A
  • Antigen / bacteria / virus / pathogen binds to B cell
  • Antigen / bacteria / virus / pathogen binds to MHC (antigen)
  • T helper lymphocytes / cells bind (to B cell)
  • Cytokines (from T helper cells)
87
Q

List the different types of immune cells? (5 Marks)

A

Phagocytes

  • Macrophages - Neutrophils Lymphocytes
  • B cell
  • T helper cell
  • T killer cell
88
Q

Consequences of supressed immune function? (2 Marks)

A
  • Opportunistic infections

- Might lead to death/coma/ severe damage

89
Q

Function of macrophages. (5 Marks)

A
  • Phagocytosis
  • And antigen presentation to elicit a specific immune response
  • Phagocytosis: When they encounter a microbe they grow cytoplasmic extensions called pseudopodia
  • The microbe is enclosed in a vacuole (phagosome)
  • The phagosome fuses with the lysosome (phagolysosome)
  • Antigen presentation: antigens are reserved and picked up by the MHC proteins
  • The MHC-complex moves to the cell surface membrane
  • Thus macrophages become into antigen presenting cells.
90
Q

Describe the functions of macrophages

A
  • destroy microbes by phagocytosis,
  • By engulfing any antigens they encounter
  • The antigens are then presented on the membrane by attaching them on the major
    histocompatibility proteins
  • Antigen presentation by the macrophages.
  • This allows T-helper cells to bind to them
  • These will now activate and cause the proliferation of lymphocytes
91
Q

Describe the functions of Natural t-killer cells:

A
  • Lymphocytes
  • Recognize specific antigens
  • Bind to the antigens/MHC complexes on the surface membranes of infected cells
  • Are activated by cytokines from T-helper cells
  • When activated they release enzymes (perforin) which create pores in the membranes of
    infected cells
  • These pores allow ions and water to flow into the cells
  • Thus cells swell and burst (lysis)
  • Releasing pathogens to be killed by B-cells and macrophages
92
Q

Describe the functions of

A
  • Destroy microbes by phagocytosis
  • Release cytokines
  • Amplify inflammatory reactions by other types of cells.
93
Q

Q: Why do scientist repeat their experiments? (2 Marks)

A
  • To increase precision in measurements
  • Increase confidence in results
  • Prove results are reproducible
94
Q

Why should experiments be repeated under the same experimental conditions (or constant experimental conditions)? (2 Marks)

A
  • To see only the effect of the one variable (the independent variable)
  • To have comparable results
  • To prevent outside influences
  • Limit the impact of other variables
95
Q

Q: What does a significant variation mean? (3 Marks)

A
  • a statistical analysis
  • relating to a difference between a result derived from a hypothesis and its observed value
  • shows that it is too large to be attributed to chance
  • thus, tends to disprove the hypothesis.
96
Q

What is a peer review and why is it useful in science? (2 Marks)

A
  • The potential paper is send to other scientists (peers) to repeat the work
  • To verify if it is valid, reliable
  • If the results are significant
97
Q

Q: Describe the double blind trial and explain why it is carried out in phase 3. (3 Marks)

A
  • Patients are randomly divided into two groups
  • One group receives the drug
  • The other group receives the placebo or the existing treatment
  • Neither the patient nor those recording any changes in the patients (e.g. doctor) know
    who has received the drug and who not.
  • This reduces the chances of bias
  • To compare to existing treatments and to placebo in order to test the effectiveness of the
    new drug.
  • If there is a statistically significant improvemen
98
Q

Q: List some of the implications associated with modern protocols of drug testing by FDA. (4 Marks)

A
  • Expensive
  • Large number of patients and volunteers
  • It is carried out for a long time (economic cost)
  • Animal testing involved – cost, legal issues
  • Legal costs
99
Q

Q: What is a placebo? (1 or 2 marks)

A
  • A substance that has no therapeutic effect

- e.g. water, saline solution

100
Q

Q: Explain why placebos are used during drug testing. (2 Marks)

A
  • Inactive substance
  • That it is used as a control
  • Baseline for comparison
101
Q

What factors would have to be considered before a drug can be marketed? (4 Marks)

A
  • Effectiveness
  • To be safe, non-toxic
  • Stable (so that it can be stored for long periods)
  • Can be produced in large quantities
  • Cheap
  • Can be metabolised and removed from the body
102
Q

Define Cancer.

A
  • when the rate of cell multiplication is faster
  • than the rate of cell death
  • thus tumor growth
103
Q

What factors cause Cancer? (2 Marks)

A
  • Environment and genetic make-up combine to cause cancer.
  • Cancers are caused due to DNA damage, thus it often occurs in tissues with a high rate of
    mitosis
104
Q

Q: Explain what is meant by the term transcription factor. (2 Marks)

A
  • protein / hormone
  • regulates / switch on / activates / binds to promoter region
  • a gene / allele / mRNA synthesis
105
Q

Q: What are gatruloids? (3 Marks)

  • three dimensional
  • aggregates of embryonic stem cells (ESCs)
  • display many features of early development
A

What are the benefits of using gastruloids? (4 Marks)

  • 3D structure
  • spatial organization
  • development of organs and tissues
  • cultured ex vivo
  • showing important self-organizing events
  • showing mechanisms that underlie size and timing control in development,
106
Q

Suggest how natural selection could have led to the evolution (4 Marks)

A
  • Genetic variation in population
  • Reference to selection pressure
  • Description of a beneficial characteristic
  • Idea that these organisms with beneficial characteristics survive and reproduce
  • Passing on beneficial alleles to offspring
  • Over generations there is a change in allele frequency
  • Relevant reference to geographical/ reproductive isolation
107
Q

Define evolution. (1 Mark)

A
  • The process by which different kinds of living organism have developed (have changed in behavior, anatomy or physiology) from earlier forms over time
108
Q

Why not humans? (2 Marks)

A
  • Unethical

- More complex organisms

109
Q

What does tailored treatment mean? (2 Marks)

A
  • drugs, or other types of treatments
  • that are specific for an individual
  • to improve health or change behavior
110
Q

Q: Suggest the advantages of using a type of mouse bred with a disorder that mimics heart diseases seen in humans. (2 marks)

A
  • Control genetic make-up as humans have genetic variation
  • Unethical to carry out research in humans
  • Larger sample size can be used
111
Q

People who believe in an alternative ethical position to such absolutism are called relativists. Suggest the opinion a relativist would have with regard to using animals in research. (1 Mark)

A
  • use animals providing there is (human) benefit / idea that it is wrong to use animals for testing but there may be circumstances when it is acceptable / idea of a balance between animal suffering and (human) benefit
112
Q

Q: Absolutism is an ethical position with regard to animal testing. Suggest what is meant by the term absolutism. (2 marks)

A
  • Always acceptable to use animals
  • Regardless of suffering/ animals have no rights/animal rights not as important as human
    rights Or
  • Never acceptable to use animals
  • Animals have rights/ animals’ rights are as important as human rights/ eq
113
Q

Why is it important that the identities of reviewers of scientific papers are not given to the author(s) of the paper? (2 Marks)

A
  • To avoid bias
  • prevents the author from influencing the reviewers
  • and for the reviewers to be free to criticize without causing offence
114
Q

Suggest three reasons why it is important to present scientific findings at conferences. (4 Marks)

A
  • Allows the scientist to review their results
  • To discuss current and new ideas
  • To communicate with colleagues
  • To spark off new ideas and future projects
  • To find funding, to assess the outcome of the experiment
115
Q

Q: Do you consider that the information in this article has been obtained from reliable sources? (4 Marks)

A
  • Overall there are specific sources given
  • paragraphs are linked to references
  • Thus reliable
  • bibliography acknowledgment given at the end of the article
  • references are incomplete

Biology paper 3 (2 decks)

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