AS1 Chapter 5 - Continuity of Cells Flashcards
Past Paper Question - June 2017 Q4 c) AS1 (Revised Spec. + Legacy Material)
Q4 c) Describe and explain two features of meiosis that contribute to genetic variation. [4]
Q4 c) Independent assortment/ random alignment of homologous chromosomes; resulting in new chromosome combinations in gametes.
Exchange of genetic information (crossing over)/ recombination of genes between two chromatids/ non sister chromatids/ homologous chromosomes/ new allelic combination; [4]
Past Paper Question - June 2017 Q4 d) AS1 (Revised Spec.)
Q4 d) The cell cycle can be targeted by anti-cancer drugs such as 5’ Fluorouracil. State the stage of the cell cycle which is affected by this drug. [1]
Q4 d) DNA synthesis/ S-phase [1]
Past Paper Question - June 2017 Q4 d) AS1 (Legacy Material)
Q4 d) Nuclear division by mitosis or meiosis is followed by cytokinesis. Describe precisely how cytokinesis occurs in animal cells. [1]
Q4 d) Cleavage furrow/ invagination/ cytoplasm splits to form two daughter cells. [1]
Past Paper Question - June 2016 Q5 a)i) AS1 (Legacy Material)
Q5 The diagram below represents the eukaryotic cell cycle.
Mitosis -----> Stage X Stage X ----> G1 G1 ------> S S -------> G2 G2 ------> Mitosis (Circle)
a)i) Identify process X. [1]
Q5 a)i) Cytokinesis; [1]
Past Paper Question - June 2016 Q5 a)ii) AS1 (Legacy Material)
Q5 a)ii) Describe two changes that take place in cells during the G1 phase. [2]
Q5 a)ii) Any two from:
• Cell increases in size/volume/mass
• Protein synthesis/RNA/enzymes synthesis
• Organelles replicate/are synthesised
Past Paper Question - June 2016 Q5 a)iii) AS1 (Legacy Material)
Q5 a)iii) Describe two differences between the cell cycle in animal and plant cells. [2]
Q5 a)iii) Centrioles involved in animal cells (or converse); Cleavage furrow (by description) in animal cells/formation of cell plate (by description) in plant cells; [2]
Past Paper Question - June 2016 Q5 b) AS1 (Legacy Material)
Q5 b) Onion root tip cells require 12 hours to complete the cell cycle. The time spent in a particular stage can be estimated using the following formula:
Time in stage = Number of cells in stage
——————————— x time in minutes for cell cycle
Total number of cells counted
Actively dividing onion tissue was examined using a microscope. The table below shows the number of cells observed to be in different stages of the cell cycle. The time spent in each stage has been calculated except for metaphase.
Stage Number of cells Time in stage/mins
Interphase 20 389
Prophase 10 195
Metaphase 3 X
Anaphase 2 39
Telophase 2 39
Total number of cells 37
Using the formula and the table, calculate the time spent in metaphase by these onion cells.
(Show your working). [2]
Q5 b) 3 divided by 37
Multiply by 720 (12x60=720)
Answer = 58 minutes [2]
Past Paper Question - June 2015 Q4 c)ii) AS1 (Legacy Material)
Q4 c) Cancer occurs when cells divide more frequently than normal, resulting in a mass of cells called a tumour. One type of treatment for cancer is chemotherapy, which involves drugs which interfere with the cell cycle in cancer cells.
Two chemotherapy drugs, A and B, are effective because they prevent DNA replication within the cancer cells. This reduces the rate of cell division within a tumour.
Drug A contains platinum, a metallic element, that forms strong cross-links between the two strands in a DNA molecule.
Drug B is similar in structure to a nucleotide but contains three phosphates instead of one.
ii) Identify the precise stage of the cell cycle which is affected by both these drugs. [1]
Q4 c)ii) S/synthesis phase; [1]
Past Paper Question - June 2015 Q8 Section B AS1 (Legacy Material)
Q8 The process of meiosis results in haploid daughter cells which show genetic variation.
Give an account of the process of meiosis. Your account should include the stage at which the haploid number of chromosomes is formed and two ways in which the process results in genetic variation in daughter cells. [13]
Quality of written communication [2]
Q8 Three essential points and any ten other points from:
• at prophase 1 homologous chromosomes pair up/form bivalents
• chromosomes shorten and thicken/become visible/condense
• chiasma/chiasmata/crossing over occurs
• between non-sister chromatids/homologous chromosomes
• leads to recombinants/new allelic combinations/non-parental allelic
combinations
• which is one cause of variation (essential point)
• spindle fibres develop
• at metaphase 1 the bivalents (homologous pairs) attach to the spindle fibres
• by their centromeres
• orientation of the bivalents (homologous pairs) is random/independent assortment occurs
• which is another cause of variation (essential point)
• at anaphase 1 the spindle fibres contract
• pulling whole chromosomes to opposite poles of the cell/separating
homologous chromosomes
• this is the point at which the haploid number of chromosomes is formed (essential point)
• nuclear membranes form/two cells produced
• in prophase 2 two sets of spindle bres form at right angles to the original
• in metaphase 2 individual chromosomes (within each group) attach to the spindle fibres
• by their centromeres (allow once)
• in anaphase 2 the spindle fibres contract (allow once)
• pulling the chromatids (do not accept chromosomes) to opposite poles
• resulting in four groups of (new) chromosomes
• nuclear membranes form/four cells produced (allow once)
• chromosomes decondense/become thinner/less visible
Past Paper Question - January 2014 Q3 a)i)+ii)+iii)+b)i)+ii) AS1 (Legacy Material)
Q3 Photograph 1.3 shows six photomicrographs of animal cells at different stages of mitosis. These are labelled A–F.
(a) (i) Identify the stages shown in photomicrographs A–D.
A ____________________
B ____________________
C ____________________
D ____________________ [4]
ii) Identify the structures labelled X and describe fully their role in the
process of mitosis. [3]
iii) The photomicrographs A–F do not show the stages of mitosis in the correct sequence. Rearrange the letters A–F to show the correct sequence of the stages. [2]
b)i) Identify the process that is beginning to happen in E. [1]
ii) Outline how this process would be different in a plant cell. [1]
(Go do this past paper)
Q3 i) A: telophase;
B: anaphase;
C: prophase (not interphase, as question concerns mitosis);
D: metaphase; [4]
(ii) Spindle fibres;
spindle fibres attach to the centromeres (at the start of metaphase); contraction of the spindle fibres pulls the chromatids apart (during anaphase); [3]
(iii) C, D, F, B, A, E; [2]
b) i) Cytokinesis; [1]
(ii) A cell plate would form (instead of a cleavage furrow); [1]
Past Paper Question - June 2014 Q2 a)+b) AS1 (Legacy Material)
Q2 The diagram below shows two stages in the process of nuclear division by meiosis. The diploid number of the cell shown in stage A is 4.
a) Identify stage B. [1]
b) Describe the behaviour of the chromosomes between stage A and stage B. [4]
(Go do this past paper question)
Q2 a) Telophase I/Prophase II; [1]
b) Any four from:
• homologous chromosomes pair up/bivalents form
• chiasmata form/crossing over occurs
• (homologous pairs/bivalents) line up at the equator of the cell
• spindle fibres attach to centromeres
• homologous chromosomes are separated/pulled apart (as a result of
spindle fibres shortening)
• chromosomes may be enclosed in a new nuclear envelope [4]
Past Paper Question - January 2013 Q3 a)ii) AS1 (Legacy Material)
Q3 a)ii) Identify the specific stage in the cell cycle when DNA replicates to form the two chromatids. [1]
Q3 a)ii) S/synthesis phase (of interphase); [1]
Past Paper Question - January 2013 Q3 a)i)+b)i)+ii)+c) AS1 (Legacy Material)
Q3 a) The diagram below represents a chromosome as it would appear during prophase of mitosis.
i) Name the structure labelled X. [1]
b)i) The diagram below shows a cell at a stage of mitosis.
Name the stage of mitosis shown in the diagram. [1]
ii) Describe how the arrangement of the chromosomes would differ in a cell at the same stage of the first division of meiosis. [2]
c) An outline of a cell-surface membrane is shown below. Within this outline draw the cell shown in b)i) as it would appear at the next stage of mitosis. [2]
(Go do this past paper question)
Q3 a)i) Centromere/kinetochore; [1]
b) i) Metaphase; [1]
ii) Paired homologous chromosomes/bivalents attached to spindle; chiasmata/crossing over (that formed during prophase) visible; [2]
c) Chromatids pulled apart [chromatids shown as V-shaped, with centromeres pointing towards poles];
with attached spindle fibres missing the sections between the chromatids (with other spindle fibres complete); [2]
Past Paper Question - January 2012 Q3 a) AS1 (Legacy Material)
Q3 Yew trees have been used as a source of a group of drugs called taxanes. Taxanes interfere with the normal functioning of the microtubules in the cell, and so inhibit mitosis. They are used to treat certain types of cancer since they prevent cell division and therefore reduce tumour growth.
The effect of various concentrations of a taxane drug on percentage inhibition of mitosis is shown in the graph below.
a) Describe, as fully as possible, the effect of increasing taxane concentration on the % inhibition of mitosis. [3]
(Go do this past paper question)
Q3 a) At low levels (0–4), a rise in taxane causes a small rise in inhibition/inhibition is low;
Not just inhibition is slow.
at medium levels (3–6/4–5), a rise in taxane causes a large increase in inhibition;
Not just inhibition increases more rapidly.
at high levels of taxane (6–8), there is little further rise in inhibition/inhibition levels off/inhibition is nearly complete;
Not just inhibition increases less rapidly/stops. [3]
Past Paper Question - January 2012 Q3 b) AS1 (Legacy Material)
Q3 Yew trees have been used as a source of a group of drugs called taxanes. Taxanes interfere with the normal functioning of the microtubules in the cell, and so inhibit mitosis. They are used to treat certain types of cancer since they prevent cell division and therefore reduce tumour growth.
The effect of various concentrations of a taxane drug on percentage inhibition of mitosis is shown in the graph below.
b) Cells which have been treated with taxanes begin mitotic division, but cannot complete it. Suggest which phase of mitosis is prevented by taxanes, and give a reason for your answer.
Phase of mitosis ___________________________
Reason ___________________________________________
___________________________________________________ [2]
Q3 b) Metaphase;
taxane will interfere with the spindle formation/prevents attachment of centromere (of chromatids/chromosome);
or
Anaphase;
taxane will interfere with spindle shortening/prevents chromatids from
being pulled apart;
Must link name of phase with correct reason. [2]
Past Paper Question - June 2012 Q5 a)i)+ii) AS1 (Legacy Material)
Q5 Chromosomes are visible during mitosis and meiosis in eukaryotic cells.
a) The image below shows a karyotype of mouse chromosomes.
i) Using the karyotype, determine the haploid number for mouse cells. [1]
ii) Identify the sex of the mouse, assuming that sex determination in mice and humans follows the same model. [1]
(Go do this past paper question)
Q5 a)i) 20; [1]
ii) Male; [1]
Past Paper Question - June 2012 Q5 b)i) AS1 (Legacy Material)
Q5 Chromosomes are visible during mitosis and meiosis in eukaryotic cells.
b) Gametes in mammals are produced by meiotic cell division. Two important properties of mammalian gametes are that:
• they are haploid;
• there is genetic variation in the gametes produced by any one individual.
i) Identify the precise phase of meiosis which results in the haploid condition and describe what happens during this phase. [2]
Q5 b)i) Anaphase I;
homologous chromosomes are separated; [2]
Past Paper Question - June 2012 Q5 b)ii) AS1 (Legacy Material)
Q5 Chromosomes are visible during mitosis and meiosis in eukaryotic cells.
b) Gametes in mammals are produced by meiotic cell division. Two important properties of mammalian gametes are that:
• they are haploid;
• there is genetic variation in the gametes produced by any one individual.
ii) There are two ways in which genetic variation arises. In each case, identify the precise phase of meiosis which results in genetic variation and describe what happens during the phase.
- _____________________________________________________________________
_______________________________________________________________________
_______________________________________________________________________ - _____________________________________________________________________
_______________________________________________________________________
______________________________________________________________________ [3]
Q5 b)ii) Prophase I, crossing over takes place (between homologous chromosomes);
Metaphase I, bivalents assort independently/line up randomly (before being separated); [3]
Past Paper Question - June 2012 Q5 c)i) AS1 (Legacy Material)
Q5 Chromosomes are visible during mitosis and meiosis in eukaryotic cells.
c) One stage of meiosis involves sister chromatids being pulled to opposite ends of the cell. In order to allow this, a protein called cohesin, which binds sister chromatids together, must be hydrolysed by an enzyme called separase.
(i) Identify the stage of meiosis during which sister chromatids are pulled to opposite ends of the cell.
Q5 c)i) Anaphase II; [1]
Past Paper Question - June 2012 Q5 c)ii) AS1 (Legacy Material)
Q5 Chromosomes are visible during mitosis and meiosis in eukaryotic cells.
c) One stage of meiosis involves sister chromatids being pulled to opposite ends of the cell. In order to allow this, a protein called cohesin, which binds sister chromatids together, must be hydrolysed by an enzyme called separase.
ii) Explain the term ‘hydrolysed’. [2]
Q5 c)ii) The breakdown of large molecules into sub-units;
where water is added; [2]
Past Paper Question - June 2012 Q5 c)iii) AS1 (Legacy Material)
Q5 Chromosomes are visible during mitosis and meiosis in eukaryotic cells.
c) One stage of meiosis involves sister chromatids being pulled to opposite ends of the cell. In order to allow this, a protein called cohesin, which binds sister chromatids together, must be hydrolysed by an enzyme called separase.
iii) State the products of the hydrolysis of cohesin. [1]
Q5 c)iii) Amino acids/peptides; [1]
Past Paper Question - June 2011 Q1 AS1 (Legacy Material)
Q1 The following statements describe events within stages of meiosis.
Identify the stage in each case.
• Bivalents are formed when homologous chromosomes pair
______________________________________
• Chromatids separate and are pulled to opposite poles
______________________________________
- Four haploid nuclei are formed
______________________________________ - Chiasmata occur
______________________________________ [4]
Q1
Prophase I;
anaphase II;
telophase II;
prophase I;
Must refer to relevant I and II divisions [4]
Practical Work - Preparing and staining root tip squashes
What species of plant is best used for this experiment and why?
The root tips of broad beans are a good source as they are relatively easy to manipulate.
Practical Work - Preparing and staining root tip squashes In plants (unlike animals), cell division takes place in ...
Specific areas