MEMORANDUM TERM 1 LIFE SCIENCES

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1 MEMORANDUM TERM 1 LIFE SCIENCES Grade 12 TERM 1 TASK 1: PRACTICAL TASK MONOHYBRID CROSSES 35 Impak Onderwysdiens (Pty) Ltd 5

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3 TASK 1: PRACTICAL TASK: MONOHYBRID CROSSINGS MEMORANDUM 1. The results support the hypothesis. If the allele combination of the parents is known then the ratio of the F1 generation can be predicted. (3) 2. (a) Allele combination of offspring. (2) (b) Allele combination of parents. (2) (c) Recessive alleles, dominant alleles, same contrasting alleles. (any two) (2) 3. Genotypes of offspring in three different crossings Genotypes RR Rr rr Crossings A 10 Crossing B Crossing C Data correctly entered for three models (3 x 1) Caption (1) Column headings correct (1) Row headings correct (1) Different genotypes of the offspring of the three crossings 20 Number of offspring Crossing 1 Crossing 2 Crossing 3 rr Homozygous white Rr Heterozygous red RR Homozygous red Rubric to assess graph: Correct type of graph 1 Title of graph 1 Correct choice and label for x-axis 1 Correct choice and label for y-axis 1 Impak Onderwysdiens (Pty) Ltd 7

4 Key 1 Width of bars 1 Appropriate scale for y-axis (constant intervals) Plotting of bars 1 one bar plotted correctly 2 two bars plotted correctly 3 three bars plotted correctly 1 (10) 5. Crossing A: If both parents are homozygous the offspring will inherit one allele from each parent and will be heterozygous. Crossing B: If one parent is homozygous and the other parent is heterozygous, there is a 50% chance that the offspring will be homozygous and a 50% chance that the offspring will be heterozygous. Crossing C: If both parents are heterozygous there is a 25% chance that the offspring will be homozygous dominant, a 50% chance that the offspring will be heterozygous and a 25% chance that the offspring will be homozygous recessive. (10) TOTAL: 35 Impak Onderwysdiens (Pty) Ltd 8

5 MEMORANDUM TERM 1 LIFE SCIENCES Grade 12 TERM 1 TASK 2: TERM 1 TEST 75 Impak Onderwysdiens (Pty) Ltd 9

7 LIFE SCIENCES GRADE 12 TASK 2 TERM 1 TEST MEMORANDUM TOTAL: 75 SECTION A QUESTION A D C D A QUESTION 1.2 (5 x 2) = [10] Nucleotide Peptide Mutation Centromere Locus [5] TOTAL SECTION: 15 SECTION B QUESTION DNA (2) Hydrogen bond 2 Phosphate 3 Deoxyribose sugars 4 Thymine 5 Cytosine (5) 2.3 Nucleotide. (1) Impak Onderwysdiens (Pty) Ltd 11

8 2.4 DNA forms two identical replicas of itself. During interphase/before cell division. Two chromatids that are formed identically. The two chromatids are identical to the parent. (any three) (3) 2.5 For table: DNA RNA 1. Double-strand molecule/paired basis. Single-strand molecule/unpaired basis. 2. Contains deoxyribose sugar. Contains ribose sugar. 3. Contains nitrogen base thymine. Contains nitrogen base uracil. 4. A is proportional to T and G is Different numbers of A, U, G and C. proportional to C. 5. Longer. Shorter. 6. Helix structure. No helix. One mark for table and 6 marks for three differences. (7) [18] QUESTION Suspect 1. (1) The DNA fingerprints of the skin that was found under the victim s nail fits the DNA of suspect 1. (2) No. (1) Hair-/skin tissue could have been placed at the crime scene. OR The DNA of the skin tissue could have been under the victim s nail before the murder was committed. OR The suspect could have been one of identical twins that have the same fingerprint. OR The samples that have been taken could have been mixed with others in the laboratory. (2) Translation. (2) Ribosome. (1) a) Isoleucine. (1) b) CAG /cytosine, adenine, guanine. (1) c) Codon. (1) d) Has arginine instead of alanine /has different amino acids. (2) GTA (2) [16] Impak Onderwysdiens (Pty) Ltd 12

9 QUESTION A Daughter chromosome /chromatid. B Spindle fibre /spindle/wire speed. (2) /two (1) /two (1) Reduction/halving of chromosome number /lets a gametophyte form/keeps the chromosome number constant from generation to generation /prevents doubling of chromosome number during fertilisation. Contributes to genetic variation. Forming of gametes. (any two) (2) Mitosis Meiosis Takes place in somatic cells. Takes place in sex organs. Nucleus divides once Nucleus divides two times. Two daughter cells are formed. Four daughter cells are formed. Daughter cells are identical to each other and to the mother cell. Daughter cells are not identical to each other and not to the mother cell. Chromosome number stays constant. Chromosome number is halved. Chromosome single on equator. During meiosis 2, the chromosomes are in homologues pairs, with each of each pair situated on each side of the equatorial. Cross-over does not take place. Cross-over takes place. Centromeres divide. Centromeres do not divide during meiosis 1. Daughter chromosomes move towards the opposite poles. One chromosome of each homologues pair moves towards the opposite pole during meiosis 1. (any five) (5) [11] QUESTION Gg 3 Gg (2) gg (1) Yes. (1) Impak Onderwysdiens (Pty) Ltd 13

10 5.1.4 (correct transparent shape) (correct shaded shape) (4) Understand that there is a 50% chance to have a normal child and a 50% chance to have a child that will suffer from cystic fibrosis. Go for genetic advice/counselling. Accept responsibility for their decision/make an informed decision. (any one) (1) AB (1) Represents separate/different entities/units. OR Discontinue variation. OR No in-between mediums. (any one) (1) Frequency of blood groups in a small human population: Blood group AB A B O Percentage (4) [15] TOTAL SECTION B: 60 GRAND TOTAL: 75 Impak Onderwysdiens (Pty) Ltd 14

11 MEMORANDUM TERM 2 LIFE SCIENCES Grade 12 TERM 2 TASK 3: CASE STUDY DIHYBRID CROSSES 35 Impak Onderwysdiens (Pty) Ltd 15

13 TASK 3: CASE STUDY DYHIBRID CROSSES MEMORANDUM SECTION A 1. Pe Pe pe pe PE PPEe PPEe PpEe PpEe Pe PPee PPee Ppee Ppee PE PPEe PPEe PpEe PpEe Pe PPee PPee Ppee Ppee 2. PPEe 4/16 PpEe 4/16 (2) 3. PPee 4/16 Ppee 4/16 (2) 4. None. The characteristics are only visible if the organism is homozygous recessive for that characteristic. (2) 5. Ratio: 1 : 1 (1) [10] (3) Step 1: B = black B = white R = rough coat r = smooth coat Step 2 Parents: BbRR X BbRr SECTION B Step 3 Meiosis: gametes BR BR br br X BR Br br br Impak Onderwysdiens (Pty) Ltd 17

14 Step 4 and 5 gametes BR BR br br BR BBRR BBRR BbRR BbRR Br BBRr BBRr BbRr BbRr br BbRR BbRR bbrr bbrr br BbRr BbRr bbrr bbrr Genotype: 2 BBRR 4 BbRR 2 BBRr 4 BbRr 2 bbrr 2bbRR Phenotype: 12 black and rough 4 white and rough [25] GRAND TOTAL: 35 Impak Onderwysdiens (Pty) Ltd 18

15 MEMORANDUM TERM 2 LIFE SCIENCES Grade 12 TERM 2 TASK 4: TERM 2 TEST 60 Impak Onderwysdiens (Pty) Ltd 19

17 LIFE SCIENCES GRADE 12 TASK 4 TERM 2 TEST MEMORANDUM TOTAL: 60 QUESTION 1 SECTION A C B A D C 5 x 2 = [10] Eutrophication Greenhouse effect Famine Recycling Monoculture 5 x 1 = [5] Burning of fossil fuels Increased carbon dioxide levels leads to an increase in temperature of the atmosphere A carbon sink absorbs carbon dioxide from the atmosphere A green plant/tree If the carbon sinks get exhausted the carbon dioxide levels will rise. 5 x 1 = [5] QUESTION 2 SECTION B Impak Onderwysdiens (Pty) Ltd 21 TOTAL SECTION A: Faecal coliforms, nitrates and phosphates. (3) 2.2 The sewage plant does not function properly because the level of faecal coliforms has increased greatly from sample A to sample B, which indicates that untreated water has been dumped in the river. (3) 2.3 Cholera /typhoid fever, /hepatitis /gastroenteritis /dysentery. (any two) (2)

18 2.4 The water in sample B is more acidic than the water in sample A. (1) 2.5 Acid mine drainage is the drainage of highly acidic water from old mineshafts to the earth s surface. (1) 2.6 Increased levels of plant nutrients will cause that plants and algae grow at an increased rate. (1) 2.7 Decreased oxygen levels as a result of the rotting of water plants that grew at increased rates because of eutrophication (high levels of nitrates and phosphates) and died thereafter because of a lack of sunlight. OR Highly poisonous levels of salts (sodium and chlorides). OR ph level drops/water is too acidic for fish to survive. (any two) (2) [13] QUESTION : 1.2 billion, 2010: more than 7 billion. (2) E.g. improvement in medicine /better hygiene /higher food production. (any two acceptable reasons) (2) E.g. too many people/exponential growth, therefore there is a food shortage/not everyone has access to food. (any valid explanation) (2) Food shortage as a result of floods /a certain geographical area is not suited for planting food /natural disasters like hurricanes destroy crops and stock decreases /droughts destroys crops /impact of changing climates on crops. (any three) (3) In certain areas of the world, land is redistributed to inexperienced farmers without the necessary knowledge of how to produce big crops. A lot of farmers do not have the necessary equipment to ensure a big crop. Smaller crops causes an increase in food prices up to a point that people cannot afford the food they need. Food producing countries put restrictions on the amount of food that they export, which causes the price of local goods to increase, including food. (any three) (3) [12] QUESTION 4 Nuclear waste is an issue because it is not bio-degradable. Figure 3 shows that there are a lot of people who still have a no-care attitude about nuclear waste storage, which has worse consequences over the long term. Ideas regarding the disposal of nuclear waste that might be mentioned in candidate s essays: Nuclear waste can have a lot of health risks for anyone who comes in contact with the waste. This includes marine life and the heating of sea water can cause a decrease in biodiversity. Impak Onderwysdiens (Pty) Ltd 22

19 Chernobyl is a good example of the problems caused by nuclear waste disposal. A more recent example was seen in Japan. Current methods of disposing of nuclear waste: Deep-sea disposal. (Marks for description and risks involved with the method. ) Deep geologic disposal. (Marks for description and risks involved with the method. ) Nuclear waste recycling. (Marks for description and risks involved with the method. ) A responsible approach to the disposal of nuclear waste is essential. (any 15) [15] TOTAL SECTION B: 40 GRAND TOTAL: 60 Impak Onderwysdiens (Pty) Ltd 23