Biology Mock 1 Don't Know Flashcards
Give 5 things that can stimulate an immune response
Pathogens
Cells from other organisms of the same species (transplants)
Abnormal body cells
Cells infected with viruses
Toxins
Describe antigenic variability
This is a type of genetic drift.
Mutations in the pathogen’s genetic material can alter the tertiary structure of the antigens, allowing it to bind to different receptors.
When this occurs, the pathogen’s antigen will not be recognised from the memory cells from the primary response, as the antigen is no longer complimentary to the receptors. Therefore, the individual won’t be able to initiate a secondary response.
This makes it difficult to make a vaccine
What is Clonal Selection and Clonal Expansion in the humoral response
Clonal selection is when the specific B- lymphocyte with a complimentary receptor to the antigen is activated
Clonal expansion is when the activated B Lymphocyte divides by mitosis, producing many clones.
Define an antibody
A protein that’s specific and complimentary to an antigen, and it’s secreted by plasma cells
Explain one way antibodies can cause the destruction of an antigen
Multiple antigens bind to the specific, complimentary binding regions of the antigen, forming antigen-antibody complexes. The antibodies cause agglutination, so the pathogen clumps together, and act as chemical markers for phagocytes, attracting them to engulf the pathogens and carry out phagocytosis
Explain why antibiotics are ineffective against viruses (3)
Some antibiotics kill bacteria by targeting bacterial specific enzymes or organelles - they are ineffective against viruses due to the virus using the host cell’s machinery - viruses are acellular
Some antibiotics work by destroying the links in the peptidoglycan cell wall of bacteria, making them more susceptible to osmotic lysis, hence killing them. Can’t destroy viruses as they don’t have a peptidoglycan wall
Some antibiotics work by inhibiting DNA replication. If a virus is a retro virus such as HIV, there’s no DNA to replicate (as it has RNA instead)
Outline how HIV replicates
1) Attachment proteins attach to receptors on CD4 helper T cells,
2) RNA is converted into DNA using reverse transcriptase, and DNA is inserted into the helper T Cell DNA. Viral DNA is transcribed into HIV mRNA.
3) The HIV mRNA is translated into new HIV proteins which are assembled into viral particles, which then explode out of the cell.
Define monoclonal antibodies
Antibodies with the same tertiary structure, produced from cloned plasma cells
Outline ethical issues with monoclonal antibodies
1) Clinical drug trials- it’s not ethical to compare it against a placebo, especially if that would mean some cases of diseases such as cancer were left untreated.
2) treatment may cause death
3) the use of animals for production may cause harm to the animal
4) human trials - not all side effects are known yet
Outline the cell cycle
Interphase:
G1- growth
S phase - DNA replication
G2 - growth
Mitosis:
1) Prophase:
-The chromosomes coil and condense, becoming visible. They appear as two sister chromatids joined at the centromere
- Centrioles migrate to the poles of the cell,
- Nuclear membrane begins to degrade
2) Metaphase:
- Chromosomes line up on the cells equator and attach to spindle fibres by their centromeres
3) Anaphase:
- Spindle fibres shorten and contract, splitting the centromere and pulling the sister chromatids to the opposite poles of the cell,
- The chromosomes are v-shaped.
4) Telophase:
- Chromosomes uncoil and become thinner,
- nuclear membrane re-forms
- cytokinesis (division of the cytoplasm) then takes place, producing new genetically identical cells
Outline binary fission
1) the circular DNA and plasmids replicate
2) the cell elongates from the middle, moving the DNA loops to the poles of the cell
3) the cytoplasm divides and a new cell wall forms
4) each daughter cell has a single copy of the circular DNA and a variable number of copies of plasmids
Read meiosis
Done
What causes downs syndrome
Non- disjunction in the 21st chromosome
What causes patau Syndrome
Non disjunction in the 13th chromosome
Why does non disjunction cause all cells in the organism to be mutated
Because all cells are derived from the diploid zygote by mitosis, and mitosis produces genetically identical cells
