2.1 The diagram below represents one cell in a phase of meiosis - NSC Life Sciences - Question 2 - 2022 - Paper 2
Question 2
2.1 The diagram below represents one cell in a phase of meiosis.
2.1.1 Identify the phase of meiosis shown.
2.1.2 Give ONE observable reason for your answer to Q... show full transcript
Worked Solution & Example Answer:2.1 The diagram below represents one cell in a phase of meiosis - NSC Life Sciences - Question 2 - 2022 - Paper 2
Step 1
2.1.1 Identify the phase of meiosis shown.
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Answer
The phase of meiosis shown in the diagram is Metaphase II.
Step 2
2.1.2 Give ONE observable reason for your answer to QUESTION 2.1.1.
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Answer
The observable reason is that individual chromosomes line up at the equator of the cell.
Step 3
2.1.3 Identify structure: (a) A
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Structure A is the cell membrane.
Step 4
2.1.3 Identify structure: (b) B
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Structure B is the spindle fibre.
Step 5
2.1.4 Describe the role of part B in the movement of chromosomes during meiosis.
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Part B, the spindle fibre, contracts or shortens to pull the chromosomes or daughter chromosomes/chromatids to opposite poles of the cell.
Step 6
2.1.5 Draw a labelled diagram of structure C as it would appear in the final phase of this meiotic division. Show the correct shading.
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The diagram of structure C in the final phase of meiosis should show unreplicated chromosomes (or chromatids) with a centromere. One of the chromosomes should be shaded, depicting it as an unreplicated chromosome.
Step 7
2.2.1 Name the process which occurs at: (a) W
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At W, the process that occurs is transcription.
Step 8
2.2.1 Name the process which occurs at: (b) Y
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At Y, the process that occurs is translation.
Step 9
2.2.2 Identify: (a) Organelle X
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Organelle X is the nucleus.
Step 10
2.2.2 Identify: (b) Molecule Z
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Molecule Z is mRNA.
Step 11
2.2.3 State TWO locations of DNA in a cell, other than in the nucleus.
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Two locations of DNA in a cell, other than in the nucleus, are in the mitochondria and chloroplasts.
Step 12
2.2.4 Describe the process at W.
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The process at W involves the unwinding of the double helix of DNA, where the hydrogen bonds break to form two separate strands. One strand serves as a template for synthesizing mRNA, which is complementary to the DNA sequence.
Step 13
2.2.5 Name the: (a) DNA base triplet that codes for serine.
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The DNA base triplet that codes for serine is TCG.
Step 14
2.2.5 Name the: (b) First TWO amino acids coded for by molecule Z in the diagram (the molecule is read from left to right).
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The first two amino acids coded for by molecule Z are tyrosine and proline.
Step 15
2.2.6 What is the change in the sequence of nitrogenous bases in a DNA molecule called?
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The change in the sequence of nitrogenous bases in a DNA molecule is called a gene mutation.
Step 16
2.2.7 The codon CUU (last codon) on molecule Z changed to CCU. Explain the effect it would have on this particular protein molecule.
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The change from codon CUU to CCU would alter the last amino acid incorporated into the protein from leucine to proline, which could affect the protein's structure and function.
Step 17
2.3.1 Explain why paternity of the boy could not be established using blood groups only.
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Paternity could not be conclusively established using blood groups only because multiple males can share the same blood group, making it impossible to determine the biological father based solely on this information.
Step 18
2.3.2 Who is the biological father of the boy according to the DNA profiles?
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According to the DNA profiles, male 2 is the biological father of the boy.
Step 19
2.3.3 Explain your answer to QUESTION 2.3.2.
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The explanation for this conclusion is that the DNA profiles show matching bands between the boy and male 2, indicating genetic similarity, which is not found with male 1.
Step 20
2.3.4 State ONE other use of DNA profiling.
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One other use of DNA profiling is tracing missing persons.
Step 21
2.4.1 State the type of dominance shown by the snapdragon plants.
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Answer
The type of dominance shown by the snapdragon plants is incomplete dominance.
Step 22
2.4.2 Give a reason for your answer to QUESTION 2.4.1.
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The reason is that the pink flowers are an intermediate phenotype, which is a blend of the red and white alleles.
Step 23
2.4.3 A gardener crossed two pink-flowered snapdragon plants. Use a genetic cross to show the ratio of the expected phenotypes in the offspring.
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In a genetic cross between two pink-flowered snapdragons, the expected phenotypic ratio in the offspring is 1 Red: 2 Pink: 1 White.
