unit 2 all cells arise from other cells Flashcards
(19 cards)
Viruses - Describe viral replication.(4)
- Attachment proteins attach to receptors; For ‘attachment protein’ accept gp41/gp120/ glycoprotein but ignore ‘receptor protein’.
- Virus injects nucleic acid (into host cell); For this mp accept ‘genetic material’ for ‘nucleic acid’?
- Host cell replicates viral nucleic acid; Accept ‘RNA/DNA’ for ‘nucleic acid’.
- Host cell produces (viral) protein/capsid/enzymes;
- Virus (particles) assembled and released (from cell);
Bacteria - Describe binary fission in
bacteria. (3)
- Replication of (circular) DNA; Accept nucleoid Reject chromosome Reject mitosis
- Replication of plasmids;
- Division of cytoplasm (to produce daughter cells);
Bacteria -Describe how bacteria
divide.(2)
- Binary fission;
- Replication of (circular) DNA;
- Division of cytoplasm to produce 2 daughter cells;
- Each with single copy of (circular) DNA;
Eukaryotic division - What is a tumour?
(2)
- Mass of cells; Accept abnormal growth for ‘mass’
- Many cells in mitosis/dividing cells OR Uncontrolled cell division;
Eukaryotic division - Describe and
explain the arrangement of the genetic
material in prophase (2)
- Chromosomes (are) becoming visible/distinct;
- Because (still) condensing; OR Accept ‘chromosomes are condensed’ for 2 marks. Accept shorten or thicken for ‘condensed’
- Chromosomes (arranged) at random/not lined up;
- Because no spindle (activity);
Eukaryotic division - Chromosome
Behaviour in
all Stages (8)
(During prophase) 1. Chromosomes coil/condense/shorten/thicken/become visible;
2. (Chromosomes) appear as (two sister) chromatids joined at the centromere; (During metaphase)
3. Chromosomes line up on the equator/centre of the cell;
4. (Chromosomes) attached to spindle fibres;
5. By their centromere; (During anaphase)
6. The centromere splits/divides;
7. (Sister) chromatids/chromosomes are pulled to opposite poles/ends of the cell/separate; (During telophase)
8. Chromatids/chromosomes uncoil/unwind/become longer/thinner;
Eukaryotic division - Describe the role of
the spindle fibres and the behaviour of
the chromosomes during mitosis (5)
- (In) prophase, chromosomes condense; Accept chromatin for ‘chromosomes’ and for ‘condense’, shorten and thicken
- (In) prophase OR metaphase, centromeres attach to spindle fibres; 3. (In) metaphase, chromosomes/pairs of chromatids at equator/centre of spindle/cell;
- (In) anaphase, centromeres divide; 5. (In) anaphase, chromatids (from each pair) pulled to (opposite) poles/ends (of cell); Accept for ‘chromatids’, chromosomes but reject homologous chromosomes 6. (In) prophase/metaphase/anaphase, spindle fibres shorten;
Eukaryotic division – state name given to
the division of cytoplasm during the cell
cycle. (1)
cytokinesis
Eukaryotic division – Evidence for a cell in
anaphase (2)
- Chromosomes / chromatids are (in two groups) at poles of spindle / at ends of spindle; Do not accept ‘ends of cell’
- V-shape shows that (sister) chromatids have been pulled apart at their centromeres / that centromeres of (sister) chromatids have been pulled apart.
Eukaryotic division – During the cell cycle,
the amount of DNA in a cell changes.
Explain how the behaviour chromosomes causes these changes in the amount of DNA per cell (2)
(Increase) 1. Chromosomes / DNA replicates; (First decrease)
2. Homologous chromosomes separate; (Second decrease) 3. Sister chromatids separate.
Eukaryotic division - Suggest why
preventing the formation of spindle
fibres stopped the cell cycle.
- Chromosomes/centromeres cannot attach (to spindle) OR Chromosomes cannot line up (on spindle);
- (So, no) metaphase; OR
- Chromatids cannot separate (on spindle); Accept description of ‘cannot separate’ e.g cannot move to poles Ignore ‘split’
- (So, no) anaphase;
Eukaryotic division – Describe the
appearance of chromosomes in anaphase
(1)
Chromatids are being pulled to opposite poles/ends (of the cell) by spindles/spindle fibres;
Eukaryotic division - Suggest and explain
how two environmental variables could
be changed to increase the growth rate
of cells. 4)
- Increased (concentration of) glucose; 2. Increased respiration;
- Increased (concentration of) oxygen; 4. Increased respiration;
- Increased temperature;
- Increased enzyme activity;
- Increased (concentration of) phosphate;
- Increased ATP/DNA/RNA;
- Increased (concentration of) nucleotides;
- Increased DNA synthesis;
Eukaryotic division -– Req Prac 2
Suggest why the student soaked the
root tips in hydrochloric acid
- To break down links between/separate cell walls;
- Allowing the stain to pass/diffuse into the cells OR Allowing the cells to be (more easily) squashed;
Eukaryotic division -– Req Prac
2Pressing the coverslip downwards
enabled the student to observe the
stages of mitosis clearly.
Explain why.
- To break down links between/separate cell walls;
- Allowing the stain to pass/diffuse into the cells OR Allowing the cells to be (more easily) squashed;
Eukaryotic division – Req Prac 2 -
Describe how you would determine
a reliable mitotic index (MI) from tissue
observed with an optical microscope.
Do not include details of how you
would prepare the tissue observed with
an optical microscope.
- Count cells in mitosis in field of view; 2. Divide this by total number of cells in field of view;
- Repeat many/> 10 times OR Select (fields of view) at random;
Eukaryotic division – Req Prac 2 -
Describe and explain what the student
should have done when counting cells
to make sure that the mitotic index he
obtained for this root tip was accurate.
- Examine large number of fields of view / many cells; Mark as pairs only Accept large number / 20 or more for many
- To ensure representative sample; Accept typical / reliable OR
- Repeat count;
- To ensure figures are correct; OR
- Method to deal with part cells shown at edge /count only whole cells; 6. To standardise counting;
Eukaryotic division – Req Prac 2 -
suggest why different student may get a
different mitotic index using the same
methos (assume no errors) (2)
- (Garlic) grown for different lengths of time OR (Garlic) grown in different conditions; Accept suitable descriptions of conditions, eg in different temperatures
- The root tips from different (garlic) plants/roots/bulbs/species;
- Single field of view is not representative of a root tip OR Different fields of view are different samples;
Eukaryotic division -The scientists
measured the percentage change in
tumour volume
Suggest why they recorded both percentage change and tumour volume.(2)
Percentage change
- To allow comparison as tumours may differ in volume/size (at the start of the investigation);
Tumour volume
- (As) tumours may differ in length/width/shape OR (As) volume is (best) indication of the number of cells in tumour;
