CELL DIVISION MITOSIS ANSWERS TO PAST PAPER QUESTIONS

Transcription

1 CELL DIVISION MITOSIS ANSWERS TO PAST PAPER QUESTIONS

2 Question Marking details 1 (a) (i) Telophase (1) Accept cytokinesis Metaphase (1) Any reference to meiosis penalise 1 mark (ii) Chromosomes Accept chromatids Reject chromatin/ spindle fibres (iii) DNA is found( in other parts of the cell)(1) in mitochondria (1) Reject chloroplast Marks available AO1 AO AO3 Total Maths Prac 1 1 (b) (4 days = 96 hours) 96/19 = 5 cycles (accept 5.05 cycles) Evidence of 5 cycles e.g. 96/19 or 5 cycles/ 5.05 cycles/ 5.1 cycles = 1 mark x 5 (accept x 5.05/5.1 ) = / / = marks = 9.6 x 10 5 cm -3 (accept 9.96 x 10 5 cm -3 / 1.0 x 10 6 ) = 3 marks Question 1 total

3 Question Marking details 7 Indicative content: A: Cell division Mitosis DNA mass doubles, then halves/ returns to same content one cell cycle is within 4 hours B: DNA mass DNA replication occurs during interphase Causing DNA to double After interphase DNA mass remains constant After interphase DNA present as chromosomes/ chromatids Mass DNA halves at telophase/ cytokinesis when nuclear membrane reforms Marks available AO1 AO AO3 Total Maths Prac C: Cell mass Interphase: mass of cell increases As does cell size Mass of cell continues to increase due to replication of DNA / organelles and possibly due to formation of spindle fibres cell undergoes cytokinesis and mass of cell halves 1

4 7-9 marks Indicative content of this level Correct identification of mitosis with explanation Detailed explanation of changes in DNA mass Detailed explanation of changes in cell mass The candidate constructs an articulate, integrated account, correctly linking relevant points, such as those in the indicative content, which shows sequential reasoning. The answer fully addresses the question with no irrelevant inclusions or significant omissions. The candidate uses scientific conventions and vocabulary appropriately and accurately. 4-6 marks Indicative content of this level Correct identification of mitosis possibly with explanation Either explanation of changes in DNA mass Or explanation of changes in cell mass The candidate constructs an account correctly linking some relevant points, such as those in the indicative content, showing some reasoning. The answer addresses the question with some omissions. The candidate usually uses scientific conventions and vocabulary appropriately and accurately. 1-3 marks Indicative content of this level Either Correct identification of mitosis possibly with explanation or brief explanation of changes in DNA mass Or Brief explanation of changes in cell mass 13

5 The candidate makes some relevant points, such as those in the indicative content, showing limited reasoning. The answer addresses the question with significant omissions. The candidate has limited use of scientific conventions and vocabulary. 0 marks The candidate does not make any attempt or give a relevant answer worthy of credit. Question 6 total

6 Marks Available Question Marking details AO1 AO AO3 Total Maths Prac 4 (a) Staining/ add a dye/ add correct named dye (b) Prophase B Metaphase C and E Anaphase F Telophase A and D 6 correct answers = 3 marks 4/5 correct answers = marks /3 correct answers = 1 mark 0/1 correct answers = 0 marks (c) (i) 1.8 = marks If incorrect 1 mark only for any of: 6/47 x rounded to NOT 13 (ii) Answer must be comparative higher mitotic index closer to the tip/ora (1) {higher rate of growth/higher rate of cell division/ shorter cell cycle/ mitosis takes place more rapidly/ more cells undergoing mitosis} / ORA (1) (iii) {Repeat/ increase sample} and calculate a mean (1) Accept average

7 Question Marking details (d) Any four (x1) from: A. mitotic index only gives information about cell division OR mitotic index does not take into account cell {length/ size} (1) B. cells increase in size during growth/ OR (cell) growth can also be measured by cell {size/ length} OR {cells get longer/ bigger} when they grow (1) C. {cells are {longer/ bigger} {further from root tip/ at 1.8mm} OR cells are {shorter/ smaller} {closer to the root tip/ at 0.mm} OR more {mitosis/ cell division} {at/ closer to} root tip OR less {mitosis/ cell division} further from root tip} (1) D. Growth is a combination of cell division and increase in size (1) E. Use of data (1) (e) Any three (x1) from: cells may be damaged/ broken(1) NOT squashed not stained enough (to see chromosomes)/ chromosomes not visible/ blurred image/ poor resolution (1) layers of cells overlap (1) {non-random selection of /lack of consistency in how part cells are included in} fields of view (1) Marks Available AO1 AO AO3 Total Maths Prac Question 4 total

8 AS UNIT BY1 Question Answers/Explanatory Notes Marks Available 1. (a) Structure Plant cell Animal Cell Centrioles X / Mitochondria / / Chloroplasts / X (1 for each column) [] (b) (i) Correct diagram showing double membrane with Inner membrane folded. [1] Any labels from matrix, crista, intermembrane space, double membrane, stalked particles, DNA, ribosomes. [] (ii) Aerobic respiration / ATP production (not: respiration) [1] (iii) Muscle cell / liver cell/sperm/pancreas/epithelial cell from small intestine/neurone/companion cell. [1] (iv) High requirement for energy for contraction/sperm movement / for chemical activity/high metabolic activity/active transport. [1] (not: exercise) [Total 8 Marks]. (a) A interphase (not: resting phase). B mitosis (not: cell division). C prophase. [3] (b) (i) Metaphase - both chromosomes on equator, chromatids either side. [1] Anaphase 4 V or U shaped, centromere pointing towards centrioles. [1] (ii) Nucleotide synthesis, replication of DNA, replication of organelles, protein synthesis, growth, synthesis ATP.AVP. (Any ) [] [Total 7 marks] 1

9 Question Answer Mark 6. (a) (i) J K L H I 1 (ii) I = telophase 1 L = metaphase 1 (b) (i) interphase 1 (ii) ATP production/ metabolically active; Replication of DNA; NOT synthesis/ doubling {Making/ replacing} new organelles/ replication of mitochondria/ chloroplasts NOT replication of organelles Protein synthesis; Cell increase in size (not growth) (any two) (c) DNA Doubled / DNA content increased from 0 to 40 1 and then halved (to maintain DNA content) (in two daughter 1 cells.) (ignore reference to chromosomes) (d) Two genetically identical daughter cells are produced; {Genetically identical/ clone} of parent cell. (Total 10 marks) 6

10 GCE BIOLOGY - BY1 Mark Scheme - January 013 Question Marking details Marks Available 1. (a) (i) Stage A telophase; Stage C metaphase; (ii) Centromeres split/ divide; Chromatids/ chromosomes are being pulled to (opposite) poles; (due to) contraction/ shortening of the spindle (fibres); (b) (i) Interphase; 1 (ii) The (quantity of) DNA has doubled / (quantity of) DNA changes from 6 to 1; NOT increase 1 (iii) Meiosis; (correct spelling) (At the end of the cell cycle) the (quantity) of DNA has been halved (and halved again) / can describe with numbers /involves (consecutive) divisions; Ignore reference to chromosomes Question 1 total [8] 1

11 Question Marking details 4 (a) Any 4 from 1. {nuclear membrane / nucleolus} disappear;. chromosomes {shorten / thicken / contracts / condense} / chromatin condenses; 3. (appear as) {two / pair / sister} chromatids; NOT pairing up 4. chromatids joined at centromere; 5. spindle forms; Reject ref to centrioles making spindle fibres Accept labelled diagram for 3, 4 and 5 Marks Available Max 4 (b) 5/100 x (4x60) or (4 x 60)/0 = 7 Correct Answer = marks correct calculation, incorrect answer = 1 mark (c) Any 3 from 1. both show interphase because DNA {doubles / changes from to 4 / replicates}; NOT DNA increases unqualified. (with vincristine) there is {no halving of DNA / DNA does not decrease from 4 to arbitrary units}; 3. (lack of spindle fibres) prevents chromatids being pulled to the {poles / ends of spindle}(in anaphase); allow chromosomes 4. therefore no cytokinesis / no separation into two cells; 5. daughter cells not produced Max 3 (d) meiosis produces genetically different cells AND mitosis produced {genetically identical cells / clones}; meiosis halves chromosome number AND mitosis maintains chromosome number / cells produced by meiosis are haploid AND those by mitosis are diploid ; Question 4 total [11] 4

12 Mark Scheme General Certificate of Education (A-level) Biology Unit : The Variety of Living Organisms June 01 Question Marking Guidelines Marks Comments 4(a) 1. Growth / increase in cell number;. Replace cells / repair tissue / organs /body; 3. Genetically identical cells; 4. Asexual reproduction /cloning; max Ignore growth of cells Ignore repair cells Reject bacteria 3. 'Produces genetically identical cells' does not reach MP1 as well as MP3 4. Allow example or description 4(b)(i) (Ensures) representative (sample); 1 Accept find some cells in mitosis/not in interphase. Accept 'more reliable' only if linked to percentage (of cells).'improves reliability' on its own does not gain this mark Neutral: Large sample 4(b)(ii) 1. A = metaphase;. Chromosome / chromatids lie on equator; 3. B = anaphase; 4. Chromatids /chromosomes separating / moving apart / moving to poles; 4. Reject homologous chromosomes Allow centre/middle 4. Reject homologous chromosomes 4(c) hours / 10 minutes;; Allow 1 mark if working shows candidate understood that mitosis would take 10% 6

13 Mark Scheme General Certificate of Education (A-level) Biology BIOL January 013 Question Marking Guidance Mark Comments 8(a) 1. Strands separate / H-bonds break;. DNA helicase (involved); 3. Both strands/each strand act(s) as (a) template(s); 4. (Free) nucleotides attach; 5. Complementary/specific base pairing / AT and GC; 6. DNA polymerase joins nucleotides (on new strand); 7. H-bonds reform; 8. Semi-conservative replication / new DNA molecules contain one old strand and one new strand; 6 max 1. Q Neutral: strands split 1. Accept: strands unzip 4. Neutral: bases attach 4. Accept: nucleotides attracted 6. Reject: if wrong function of DNA polymerase 8. Reject: if wrong context e.g. new DNA molecules contain half of each original strand 8(b)(i) 18; 1 Do not accept (b)(ii) 10; 1 8(b)(iii) 1. Horizontal until 18 minutes;. (Then) decreases as straight line to 0 m at 8 minutes; Allow +/- one small box. Allow lines that start from the wrong place, ending at 0 at 8 minutes 8(c)(i) Two marks for correct answer of or 19.7;; One mark for incorrect answers in which candidate clearly multiplies by 0.8; Accept 19hrs 41mins Allow one mark for incorrect answers that clearly show 8% of 4 (hours) 8(c)(ii) 1. No visible chromosomes/chromatids;. Visible nucleus; 1 max 8(c)(iii) D (no mark) 1. Lower % (of cells) in interphase / higher % (of cells) in mitosis/named stage of mitosis;. (So) more cells dividing / cells are dividing quicker; 1. Accept: less or more instead of % 1. Do not accept: higher % (of cells) in each/all stage(s). Accept: uncontrolled cell division. Do not award if Tissue C is chosen 10

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