Download Life Sciences Grade 12 Exam Question Paper: Section A and more Exams Biology in PDF only on Docsity!
ORIENT ISLAMIC SCHOOL
MARKS: 70 TIME: 60min
EXAMINER: MR I THOMPSON MODERATOR: MR S KHARSANY This question paper consists of 6 pages.
INSTRUCTIONS AND INFORMATION
Read the following instructions carefully before answering the questions.
Answer ALL the questions. Write ALL the answers in the ANSWER BOOK. Start the answers to each question at the top of a NEW page. Number the answers according to the numbering system used in this question paper. Present your answers according to the instructions of each question. ALL drawings should be done in pencil and labelled in blue or black ink. Only draw diagrams or flow charts when asked to do so. The diagrams in this question paper are NOT all drawn to scale. Do NOT use graph paper. Non-programmable calculators, protractors and compasses may be used. Write neatly and legibly.
MARCH 2013
GRADE 12 LIFE SCIENCES
SECTION A
QUESTION 1
1.1 Various options are provided as possible answers to the following questions. Choose the correct answer and write only the letter (A – D) next to the question number (1.1.1 – 1.1.5) in the ANSWER BOOK, for example 1.1.7 D. 1.1.1 In a breeding experiment between a parent showing the dominant phenotype and a parent showing the recessive phenotype, the offspring showed equal proportions of the dominant and recessive phenotypes. Which ONE of the following statements is TRUE? A Both parents were heterozygous. B Both parents were homozygous. C Both parents carry at least one recessive gene. D Only one parent carried at least one recessive gene. 1.1.2 In humans, the sex of a child is determined by the … A mother's gametes. B autosomes. C father's gametes. D XX chromosomes of the mother. 1.1.3 Which component is NOT directly involved in translation? A mRNA B DNA C tRNA D ribosome 1.1.4 A red flowered plant is incompletely dominant (R) to white flowered plants (W). Which of the following is correct? In the F1 generation the offspring are... A 100% red. B 100% white. C 100% pink. D 50% pink. 1.1.5 In rabbits the dominant allele (B) produces black fur and the recessive allele (b) produces white fur. Study the table below showing the genotypes of four rabbits. If rabbits 1 and 3 were mated together and had 12 offspring, what % would you expect to be black? A 25 B 50 C 75 Rabbit 1 2 3 4 Genotype BB Bb Bb bb
2.1 Is muscular dystrophy a dominant or recessive characteristic? Give ONE observable reason for your answer. (2) 2.2 Give the genotypes of A, & C. Use N for the dominant and n for the recessive gene. (2) 2.3 If D and E have another child, what is the chance that it will have muscular dystrophy? Show ALL your working! (7) (11) Question 3 The following diagram represents the nucleus of a diploid cell: Give the number of each of the following in the cell shown above, at the beginning of meiosis. 3.1 Chromatids (1) 3.2 Chromosomes (1) 3.3 Pairs of homologous chromosomes (1) 3.4 Number of chromosomes in each cell after meiosis (1) 3.5 Centromeres (1) ( 5 ) Question 4 Read the following passage and answer the questions that follow. Thousands of wildebeest were migrating across the great plains of the Serengeti in Africa. Some of them were large, some small, some strong and some weak. Lions followed the wildebeest, catching and eating the slowest ones. Water was scarce and only the strongest were brave enough to stop to drink from the waterholes. 4.1 Identify ONE phrase in this passage which describes variation among the wildebeest. (1) 4.2 Explain how Darwin's idea of evolution by natural selection can be applied to this passage. (4) (5)
Key: Female Male Blood group O W X Blood group A Blood group B Blood group O Tortoise 1 Tortoise 2
QUESTION 5
The pedigree diagram below shows the blood groups of individuals of a family. The blood groups are indicated inside the circle or square. The blood groups of individuals W and X are not indicated. 5.1 Write down all the possible genotypes of individuals: (a) W, and (b) X (4) 5.2 Haemophilia is a blood clotting disorder. Explain why mainly males suffer from this disorder. (3) (7) QUESTION 6 Darwin noticed different species of tortoises on the Galapagos islands. Two of these tortoises, which are drawn to scale, are shown below:
LIFE SCIENCES GRADE 12 Memo MARCH QUARTERLY TEST Section A Question 1 1.1.1 C√√ 1.1.2 C√√ 1.1.3 B√√ 1.1.4 C√√ 1.1.5 D√√ 2X5 = (10) 1.2.1 Phenotype√ 1.2.2 Karyotype√ karyogram 1.2.3 Genetic engineering√ modification 1.2.4 Polygenic√ 1.2.5 Gene√ 1.2.6 Bivalent√ tetrad 1.2.7 Genome√ 1.2.8 Chiasma√ 1.2.9 Heterozygous√ hybrid 1.2.10 Nucleotides√ 10x1 = (10) SECTION A: [20] Section B Question 2 2.1 Muscular dystrophy is a recessive characteristic√. A and partner are normal√ and have a child with muscular dystrophy√. (If muscular dystrophy was dominant then at least one parent of D would have had this condition in order to get the result shown in the diagram.) (2) 2.2 A – Nn√ C - nn√ (2) 2.3 P1 Phenotype female with MD x normal male √ Genotype nn x Nn√ Meiosis, Gametes n or n x N or n√ Fertlization√ N n n Nn nn n Nn nn √ F1 √ Therefore, there is a 50% chance of their next child having muscular dystrophy. √ (7) [11]
Question 3 3.1 16 chromatids√ 3.2 8 chromosomes√ 3.3 4 pairs of homologous chromosomes√ 3.4 4√ 3.5 8 centromeres√ [5] Question 4 4.1 “Some large, some small”P/ “some strong and some weak”. (1) 4.2 Variation in the wildebeest populationP slow and weakP OR some large and strongP were eaten by the lionsP surviveP and do not pass on their characteristics to their offspringP and pass on their favourable characteristics to their offspringP max 2 If this process continues from generation to generation the characteristic of the population will change, ie. NATURAL SELECTION of favourable characteristicsP (4) [5] Question 5 5.1. (a) IAIB^ P or ABP (1) (b) IAiP, IBi P, iiP or AOP BOP OOP (3) 5.2 It is a sex-linkedPdisease caused by a recessive alleleP carried on the XP chromosome Males need only one recessive allelePto have the disease because they have the XY combination, while females have to have both recessive allelesP to have haemophilia because they have the XX combination any 3 (3) (7 )
TOTAL = [70]
