topic 2 errors

Describe binary fission in bacteria

1. Replication of circular DNA

2. Replication of plasmids

3. Division of cytoplasm

How can increasing the temperature increase the growth rate of cells

Enzyme activity increases

Describe in 2 different ways the arrangement of the genetic material shown in the above image

1. chromosomes are still becoming visible / distinct

2. still condensing

3. chromosomes not lined up

4. no spindle fibre activity yet

name the fixed position of a gene on a DNA molecule

Loci

Explain the changes of chromosomes and mass of DNA in different nuclei at prophase, telophase, and in an egg cell

Explain how a phagocyte destroys a pathogen present in the blood (3)

1. phagocyte engulfs pathogen

2. forming vesicle / phagosome, and fuses with lysosome

3. lysosome digests / hydrolyses pathogen

Mice in Group H were injected with 2 mg kg–1 of monoclonal antibody. The monoclonal antibody was in a solution of concentration 500 mg dm–3

(a) Suggest and explain 4 further investigations that should be done before this ADC is tested on human breast cancer patients.

1. test on healthy humans to check safety / for side effects

2. test on different animal eg rat to test for side effects and safety

3. see if repeated doses stop tumour from regrowing

4. test different concentrations of ADC to find suitable /safe dosage

Describe how the human immunodeficiency virus (HIV) is replicated once inside helper T cells (TH cells). (4)

1. Reverse transcriptase converts viral RNA to DNA and

2. viral DNA is incoorperated into TH cell DNA / genome

3. viral DNA is transcribed to viral mRNA

4. viral mRNA is translated into viral proteins for the assembly of a new viral particle

Give 4 types of cell that stimulate an immune response

1. pathogen

2. cell from another organism / transplant

3. virus infected cell

4. abnormal / cancer / tumour cell

A disulfide bridge is labelled in the diagram above. What is the role of the disulfide bridge in forming the quaternary structure of an antibody? (1)

Joins two different polypeptides

Define a monoclonal antibody

antibody with the same tertiary structure

describe and explain the role of antibodies in stimulating phagocytosis (2)

1. antibodies bind to antigen / are markers

2. attract phagocytes

what can you conclude about the effectiveness on each injection on the immune response of these mice

1. Mean (antibody concentration) increases;

2. 1st injection protects some mice/1 mouse/2 mice OR 1st injection causes primary (immune) response/memory cell production;

2. and 3. Accept correct reference to number of unprotected mice

3. 2nd/3rd injection protects most/all mice OR 2nd/3rd injection causes secondary (immune) response OR 2nd/3rdinjection uses memory cells;

4. Because antibody at/above protective level/2.1;

5. Antibody decreased (rapidly after 3rd injection);

6. No mice protected after 180 days OR Injections/vaccine not effective in long term OR Booster required (when antibody below protective level/after 120/180 days);

7. One mouse (after first injection) has big response/already had meningitis/antigen;

After an injection of a meningitis vaccine, scientists hypothesised that memory B cells had formed in mice.

Suggest and explain a practical method the scientists could use to test this hypothesis (2)

1. inject meningitis antigens / vaccine again / inactive antigen

2. memory cells present if faster / more rapid production or higher concentration of antibodies, so signs / symptoms do not show