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 QUE... 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
Identify the phase of meiosis shown.
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Answer
The phase of meiosis shown in the diagram is Metaphase II.
Step 2
Give ONE observable reason for your answer to QUESTION 2.1.1.
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Answer
During Metaphase II, individual chromosomes line up at the equator of the cell.
Step 3
(a) A
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A represents the cell membrane.
Step 4
(b) B
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B represents the spindle fibre.
Step 5
Describe the role of part B in the movement of chromosomes during meiosis.
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The spindle fibres contract and shorten to pull the chromosomes (daughter chromosomes/chromatids) to opposite poles of the cell.
Step 6
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 should show an unreplicated daughter chromosome/chromatid with a centromere in the final phase of meiosis (Telophase II) as represented in the provided marking scheme.
Step 7
Name the process which occurs at: (a) W
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W represents transcription.
Step 8
(b) Y
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Y represents translation.
Step 9
Identify: (a) Organelle X
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Answer
Organelle X is the nucleus.
Step 10
(b) Molecule Z
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Molecule Z is mRNA.
Step 11
State TWO locations of DNA in a cell, other than in the nucleus.
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DNA can also be found in the mitochondria and chloroplasts.
Step 12
Describe the process at W.
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At W, the double helix of DNA unwinds and the two strands separate as hydrogen bonds break. One strand serves as a template for the synthesis of mRNA, which is formed using RNA nucleotides complementary to the DNA sequence.
Step 13
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
(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 are tyrosine and proline.
Step 15
What is the change in the sequence of nitrogenous bases in a DNA molecule called?
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This change is called a gene mutation.
Step 16
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 CUU to CCU modifies the last amino acid from leucine to proline, potentially altering the protein's structure and function.
Step 17
Explain why paternity of the boy could not be established using blood groups only.
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Paternity could not be established using blood groups alone because several men could share the same blood type, making it impossible to determine the biological father.
Step 18
Who is the biological father of the boy according to the DNA profiles?
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The biological father of the boy is either male 1 or male 2 since both have some matching bands with the boy's DNA profile.
Step 19
Explain your answer to QUESTION 2.3.2.
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The mother has blood group O and the boy must have inherited his alleles from the mother; thus, either male 1 or male 2 could be the father based on the DNA matches seen.
Step 20
State ONE other use of DNA profiling.
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Another use of DNA profiling is for tracing missing persons.
Step 21
State the type of dominance shown by the snapdragon plants.
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The type of dominance shown is incomplete dominance, as evidenced by the pink offspring resulting from red and white parents.
Step 22
Give a reason for your answer to QUESTION 2.4.1.
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Incomplete dominance is indicated because the phenotype of the offspring (pink) is a blend of the phenotypes of both parents (red and white).
Step 23
Use a genetic cross to show the ratio of the expected phenotypes in the offspring.
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The genetic cross between two pink-flowered snapdragon plants (RW x RW) results in:
