AQA A Level Biology Questions With
Answers - Updated
autosomal linkage - CORRECT ANSWER- - if genes A and B occur on separate
chromosomes they are NOT linked
- if genes A and B occur on the same chromosome they ARE linked
what does autosomal linkage assume? - CORRECT ANSWER- there is no crossing
over so all linked genes remain together during meosis
sex linkage - CORRECT ANSWER- occurs when the gene for a certain
characteristic are carried on the sex chromosome
define locus - CORRECT ANSWER- the specific linear position of a particular gene
on a certain chromosome
what ratio do we expect from sex linkage - CORRECT ANSWER- 3:1
hardy-weinburg principle - CORRECT ANSWER- p + q = 1
p² + 2pq + q² = 1
what does each letter mean in the hardy-weinburg principle? - CORRECT ANSWER-
p - frequency of dominant allele
q - frequency of recessive allele
p² - frequency of homozygous dominant individuals
2pq - frequency of heterozygous individuals
q² - frequency of homozygous recessive individuals
5 assumptions of hardy-weinburg principle - CORRECT ANSWER- - large breeding
population
- random mating
- no change in allelic frequency due to mutation
- no immigration or emigration
- no natural selection
what are killer t-cells? - CORRECT ANSWER- - cytotoxic cells
- bind to non-self antigens
how to killer t-cells work? - CORRECT ANSWER-
1. virus attaches to and enters host cell
2. viral DNA causes host cell to express viral antigens on its surface
3. killer t-cells attaches to viral antigens on infected cells
4. killer t-cells induces death of infected cell (apoptosis)
,what is apoptosis? - CORRECT ANSWER- programmed cell death
how do killer t-cells destroy cancer? - CORRECT ANSWER- - cancerous =
mutations
- mutations = abnormal antigens
- killer t-cell binds to abnormal antigens
- killer t-cells induces death of cancerous cell
What does perforin do? - CORRECT ANSWER- creates holes in the cell membranes
in order to destroy the infected cell
what do helper t-cells do? - CORRECT ANSWER- - produce cytokines
- cytokines stimulate b-cells to divide into plasma and memory cells
- activate killer t-cells
define helper t-cells - CORRECT ANSWER- help humoral response by involvement
in the maturation of b-cells and by triggering the production of antibodies by b-cells
what do suppressor t-cells do? - CORRECT ANSWER- - halt immune response
- prevent wastage of energy and resources
- prevent overactive immune response
- causes reduction of white blood cells after being ill
define memory t-cells - CORRECT ANSWER- work in the same way as memory b-
cells, ensuring rapid response on subsequent exposure to the same non-self antigens
define suppressor t-cells - CORRECT ANSWER- regulate the immune response by
suppressing activity of killer t-cells and b-cells
define 'microorganism' - CORRECT ANSWER- organism that is too small to be seen
without a microscope
define 'pathogen' - CORRECT ANSWER- microorganism that causes disease
outline phagocytosis - CORRECT ANSWER-
1. phagocyte follows conc gradient of chemoattractants
2. phagocyte attaches to pathogen
3. pathogen engulfed and placed in a vesicle (phagosome)
4. lysosomes migrate to phagosome and bind with it to form a phagolysosome
--> lytic enzymes released from lysosome
5. pathogen digested
6. useful parts absorbed
7. all waste products released by exocytosis
8. non-self antigens of the pathogen displayed on the phagocytes surface (antigen-
presenting)
,where are t-cells made? - CORRECT ANSWER- thymus gland
where do b-cells mature? - CORRECT ANSWER- bone marrow
what do b-cells do? - CORRECT ANSWER- - humoral response
- release antibodies
- complementary to a specific antigen
what response are plasma cells? - CORRECT ANSWER- primary
what response are memory b-cells? - CORRECT ANSWER- secondary
outline the humoral response - CORRECT ANSWER-
1. antigen attaches to complementary antibody on b-cell
2. antigen taken into cell (endocytosis)
3. presented on cell surface membrane
4. t-helper cells bind to antigen and stimulate b-cell to divide
what does mitosis do in humoral response? - CORRECT ANSWER- - forms clones
of b-cells (plasma and memory)
- clonal response
what do clones do? - CORRECT ANSWER- each clone can produce one type of
antibody (monoclonal) which can be used in medicine
outline plasma cells - CORRECT ANSWER- - primary response
- secrete antibodies
- only survive for a few day
- slow response = person gets ill before pathogen is killed
outline memory cells - CORRECT ANSWER- - secondary response
- circulated in blood and tissue fluid
- divide rapidly
- rapid response so person doesn't get ill
what is an antibody? - CORRECT ANSWER- y-shaped globular protein produced by
b-cells
where are antibodies produced? - CORRECT ANSWER- plasma b-cells
what are antibodies made of? - CORRECT ANSWER- 4 polypeptide chains -- 2
heavy, 2 light
what are the two regions an antigen is made of? - CORRECT ANSWER- - variable
- constant
, what is special about the variable region? - CORRECT ANSWER- complementary
and specific to an antigen
what are the chains bonded by? - CORRECT ANSWER- disulphide bridge
why do antibodies have a hinge region? - CORRECT ANSWER- to allow the
antibody to move to bind to more than one antigen
what is 'monoclonal antibody production' - CORRECT ANSWER- the process by
which large quantities of antibodies (targeted against a particular antigen) can be
produced
how are monoclonal antibodies produced? - CORRECT ANSWER- - mouse
immunised by injection of antigen to stimulate production of antibodies
- plasma cells isolated from spleen
- plasma cells fuse with tumor cells to form a hybridoma
- hybridoma produces large amounts of identical antibody molecules
what is the scientific term for a tumor cell? - CORRECT ANSWER- myeloma
what can be monoclonal antibodies be used as? - CORRECT ANSWER- specific
probe to track down and purify specific protein that induced its transformation
what needs to happen to monoclonal antibodies before human use? - CORRECT
ANSWER- humanization
why do monoclonal antibodies need to be 'humanised' before used by humans? -
CORRECT ANSWER- to stop the trigger of an immune response
what are monoclonal antibodies used for? - CORRECT ANSWER- - pregnancy tests
- diagnostic tools for AIDS
- industrial production of interferon
what is a vaccine? - CORRECT ANSWER- a dead or weakened version of a disease
with relevant antigens
what is a vaccination? - CORRECT ANSWER- introduction of a vaccine containing
appropriate disease antigens into the body to induce artificial immunity
how do vaccines work? - CORRECT ANSWER- - pathogen stimulaties wbc into
making antigens
- dead or inactive pathogen enter body via injection
- antibodies stick to antigens and clump them together
- memory cells = immunity
Answers - Updated
autosomal linkage - CORRECT ANSWER- - if genes A and B occur on separate
chromosomes they are NOT linked
- if genes A and B occur on the same chromosome they ARE linked
what does autosomal linkage assume? - CORRECT ANSWER- there is no crossing
over so all linked genes remain together during meosis
sex linkage - CORRECT ANSWER- occurs when the gene for a certain
characteristic are carried on the sex chromosome
define locus - CORRECT ANSWER- the specific linear position of a particular gene
on a certain chromosome
what ratio do we expect from sex linkage - CORRECT ANSWER- 3:1
hardy-weinburg principle - CORRECT ANSWER- p + q = 1
p² + 2pq + q² = 1
what does each letter mean in the hardy-weinburg principle? - CORRECT ANSWER-
p - frequency of dominant allele
q - frequency of recessive allele
p² - frequency of homozygous dominant individuals
2pq - frequency of heterozygous individuals
q² - frequency of homozygous recessive individuals
5 assumptions of hardy-weinburg principle - CORRECT ANSWER- - large breeding
population
- random mating
- no change in allelic frequency due to mutation
- no immigration or emigration
- no natural selection
what are killer t-cells? - CORRECT ANSWER- - cytotoxic cells
- bind to non-self antigens
how to killer t-cells work? - CORRECT ANSWER-
1. virus attaches to and enters host cell
2. viral DNA causes host cell to express viral antigens on its surface
3. killer t-cells attaches to viral antigens on infected cells
4. killer t-cells induces death of infected cell (apoptosis)
,what is apoptosis? - CORRECT ANSWER- programmed cell death
how do killer t-cells destroy cancer? - CORRECT ANSWER- - cancerous =
mutations
- mutations = abnormal antigens
- killer t-cell binds to abnormal antigens
- killer t-cells induces death of cancerous cell
What does perforin do? - CORRECT ANSWER- creates holes in the cell membranes
in order to destroy the infected cell
what do helper t-cells do? - CORRECT ANSWER- - produce cytokines
- cytokines stimulate b-cells to divide into plasma and memory cells
- activate killer t-cells
define helper t-cells - CORRECT ANSWER- help humoral response by involvement
in the maturation of b-cells and by triggering the production of antibodies by b-cells
what do suppressor t-cells do? - CORRECT ANSWER- - halt immune response
- prevent wastage of energy and resources
- prevent overactive immune response
- causes reduction of white blood cells after being ill
define memory t-cells - CORRECT ANSWER- work in the same way as memory b-
cells, ensuring rapid response on subsequent exposure to the same non-self antigens
define suppressor t-cells - CORRECT ANSWER- regulate the immune response by
suppressing activity of killer t-cells and b-cells
define 'microorganism' - CORRECT ANSWER- organism that is too small to be seen
without a microscope
define 'pathogen' - CORRECT ANSWER- microorganism that causes disease
outline phagocytosis - CORRECT ANSWER-
1. phagocyte follows conc gradient of chemoattractants
2. phagocyte attaches to pathogen
3. pathogen engulfed and placed in a vesicle (phagosome)
4. lysosomes migrate to phagosome and bind with it to form a phagolysosome
--> lytic enzymes released from lysosome
5. pathogen digested
6. useful parts absorbed
7. all waste products released by exocytosis
8. non-self antigens of the pathogen displayed on the phagocytes surface (antigen-
presenting)
,where are t-cells made? - CORRECT ANSWER- thymus gland
where do b-cells mature? - CORRECT ANSWER- bone marrow
what do b-cells do? - CORRECT ANSWER- - humoral response
- release antibodies
- complementary to a specific antigen
what response are plasma cells? - CORRECT ANSWER- primary
what response are memory b-cells? - CORRECT ANSWER- secondary
outline the humoral response - CORRECT ANSWER-
1. antigen attaches to complementary antibody on b-cell
2. antigen taken into cell (endocytosis)
3. presented on cell surface membrane
4. t-helper cells bind to antigen and stimulate b-cell to divide
what does mitosis do in humoral response? - CORRECT ANSWER- - forms clones
of b-cells (plasma and memory)
- clonal response
what do clones do? - CORRECT ANSWER- each clone can produce one type of
antibody (monoclonal) which can be used in medicine
outline plasma cells - CORRECT ANSWER- - primary response
- secrete antibodies
- only survive for a few day
- slow response = person gets ill before pathogen is killed
outline memory cells - CORRECT ANSWER- - secondary response
- circulated in blood and tissue fluid
- divide rapidly
- rapid response so person doesn't get ill
what is an antibody? - CORRECT ANSWER- y-shaped globular protein produced by
b-cells
where are antibodies produced? - CORRECT ANSWER- plasma b-cells
what are antibodies made of? - CORRECT ANSWER- 4 polypeptide chains -- 2
heavy, 2 light
what are the two regions an antigen is made of? - CORRECT ANSWER- - variable
- constant
, what is special about the variable region? - CORRECT ANSWER- complementary
and specific to an antigen
what are the chains bonded by? - CORRECT ANSWER- disulphide bridge
why do antibodies have a hinge region? - CORRECT ANSWER- to allow the
antibody to move to bind to more than one antigen
what is 'monoclonal antibody production' - CORRECT ANSWER- the process by
which large quantities of antibodies (targeted against a particular antigen) can be
produced
how are monoclonal antibodies produced? - CORRECT ANSWER- - mouse
immunised by injection of antigen to stimulate production of antibodies
- plasma cells isolated from spleen
- plasma cells fuse with tumor cells to form a hybridoma
- hybridoma produces large amounts of identical antibody molecules
what is the scientific term for a tumor cell? - CORRECT ANSWER- myeloma
what can be monoclonal antibodies be used as? - CORRECT ANSWER- specific
probe to track down and purify specific protein that induced its transformation
what needs to happen to monoclonal antibodies before human use? - CORRECT
ANSWER- humanization
why do monoclonal antibodies need to be 'humanised' before used by humans? -
CORRECT ANSWER- to stop the trigger of an immune response
what are monoclonal antibodies used for? - CORRECT ANSWER- - pregnancy tests
- diagnostic tools for AIDS
- industrial production of interferon
what is a vaccine? - CORRECT ANSWER- a dead or weakened version of a disease
with relevant antigens
what is a vaccination? - CORRECT ANSWER- introduction of a vaccine containing
appropriate disease antigens into the body to induce artificial immunity
how do vaccines work? - CORRECT ANSWER- - pathogen stimulaties wbc into
making antigens
- dead or inactive pathogen enter body via injection
- antibodies stick to antigens and clump them together
- memory cells = immunity
