3.1 The diagram below shows the arrangement of two pairs of homologous chromosomes in a cell undergoing meiosis - English General - NSC Life Sciences - Question 3 - 2017 - Paper 2
Question 3
3.1 The diagram below shows the arrangement of two pairs of homologous chromosomes in a cell undergoing meiosis.
State TWO characteristics of homologous chromosomes... show full transcript
Worked Solution & Example Answer:3.1 The diagram below shows the arrangement of two pairs of homologous chromosomes in a cell undergoing meiosis - English General - NSC Life Sciences - Question 3 - 2017 - Paper 2
Step 1
State TWO characteristics of homologous chromosomes.
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Answer
Homologous chromosomes are similar in length and shape.
They carry genes for the same characteristics at corresponding loci.
Step 2
Identify structure A.
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Answer
Structure A is the spindle fiber.
Step 3
How many of EACH of the following is present in the diagram?
(a) Chromatids
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(a) There are 8 chromatids present in the diagram.
Step 4
(b) Centromeres
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(b) There are 4 centromeres present in the diagram.
Step 5
Draw a labelled diagram to show ONE of the cells that would be formed at the end of telophase I.
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The diagram should include a cell with two replicated chromosomes, cell membrane, centrioles, chromosome labels, etc.
Step 6
Give the genotype of the:
(a) Individual represented in the diagram
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(a) The genotype of the individual represented in the diagram is RrTt.
Step 7
(b) Possible gametes resulting from the arrangement of alleles represented in the diagram.
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(b) The possible gametes from the arrangement are RT, Rt, rT, rt.
Step 8
Determine the genotypes and phenotypes of their parents by doing a genetic cross.
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The phenotypes of the parents are Blood type A and Blood type B. Their genotypes are I^A i (for the father) and I^B i (for the mother).
Step 9
Identify the technique shown above.
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The technique shown is DNA profiling (or DNA fingerprinting).
Step 10
Which male is the biological father of the child?
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Male 3 is the biological father of the child.
Step 11
Explain your answer to QUESTION 3.3.2.
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The bands of the child's DNA are a combination of the DNA from each parent. The bands from Male 3 align perfectly with the child's bands, indicating a match.
Step 12
State TWO other uses of this technique.
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This technique can be used to identify organisms from their remains.
It is useful for identifying missing persons.
Step 13
What is the process called where wheat plants are altered by the insertion of genes?
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The process is called genetic engineering or recombinant DNA technology.
Step 14
State ONE other disadvantage of using insecticides.
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Insecticides can kill other beneficial organisms, harming the ecosystem.
Step 15
State TWO ways in which scientists could have improved the validity of this investigation.
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Answer
Use the same field for both experiments to minimize environmental variance.
Use the same number and species of wheat plants for both cases.
Step 16
What was the crop yield, in arbitrary units, of wheat plants without the insecticide gene grown in a greenhouse?
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The crop yield was 50 arbitrary units.
Step 17
Calculate the difference in yield between the wheat with the insecticide gene and the wheat without the insecticide gene grown in the field. Show ALL working.
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Difference in yield = Yield with insecticide gene - Yield without insecticide gene = 70 - 45 = 25.
Step 18
Describe the difference in results for the wheat with the insecticide gene grown in a greenhouse and the wheat in a field.
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In the greenhouse, wheat with the insecticide gene showed high yield, whereas wheat grown in the field showed lower yield due to varying environmental conditions.
Step 19
Suggest ONE possible reason for the difference described in QUESTION 3.4.6.
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The controlled conditions in the greenhouse can optimize growth factors, unlike the variability in field conditions.
Step 20
Give TWO possible reasons why farmers may be against the use of these insecticide-producing plants.
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Potential health impacts on consumers due to pesticide residues.
Concerns about environmental harm and interfering with natural ecosystems.
