2.1 The diagram below represents a single-stranded nucleic acid found in the nucleus - NSC Life Sciences - Question 2 - 2017 - Paper 2
Question 2
2.1 The diagram below represents a single-stranded nucleic acid found in the nucleus.
Identify the molecule represented in the diagram.
2.1.2 Identify:
(a) Part X;
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Worked Solution & Example Answer:2.1 The diagram below represents a single-stranded nucleic acid found in the nucleus - NSC Life Sciences - Question 2 - 2017 - Paper 2
Step 1
Identify the molecule represented in the diagram.
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Answer
The molecule represented in the diagram is mRNA (messenger RNA).
Step 2
Identify: (a) Part X
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Answer
Part X represents a nitrogenous base.
Step 3
Identify: (b) Sugar Y
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Answer
Sugar Y is ribose.
Step 4
Describe the process of transcription.
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Answer
Transcription is the process through which the double-stranded DNA molecule unwinds and separates at specific regions. This occurs when the hydrogen bonds between the base pairs break. A single strand of DNA serves as a template, allowing complementary RNA nucleotides from the nucleoplasm to pair with the DNA bases. The resulting mRNA is formed, which is complementary to the DNA template (i.e., A-U, C-G). This entire process is facilitated by enzymes.
Step 5
Give THREE sources of genetic variation in a species.
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Answer
Crossing over during meiosis.
Random arrangement of chromosomes.
Random fertilization.
Step 6
Differentiate between continuous variation and discontinuous variation.
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Continuous variation occurs when there is a range of phenotypes for the same characteristic, with intermediate forms. In contrast, discontinuous variation results in distinct categories of traits without intermediate forms.
Step 7
Give the: (a) DNA triplet for the third amino acid from the left in protein 2.
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The DNA triplet for the third amino acid from the left in protein 2 is ACC.
Step 8
Give the: (b) Codon for lysine.
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Answer
The codon for lysine is AAA.
Step 9
Give the: (c) Anticodon for serine.
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The anticodon for serine is UCA.
Step 10
How many of EACH of the following is involved in the formation of this protein? (a) Genes
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The number of genes involved in the formation of protein 1 is 1.
Step 11
How many of EACH of the following is involved in the formation of this protein? (b) RNA nucleotides
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The number of RNA nucleotides involved is 198.
Step 12
How many of EACH of the following is involved in the formation of this protein? (c) Codons
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The number of codons involved is 66.
Step 13
Describe how the mutation caused a change in the structure of the protein.
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The mutation caused a change in the protein structure due to one of the base triplets altering from ACG to ACC. This alteration changed the amino acid coded from cysteine to tryptophan, thereby affecting the sequence of amino acids and ultimately the protein's functionality.
Step 14
State the: (a) Independent variable
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The independent variable is the temperature.
Step 15
State the: (b) Dependent variable
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The dependent variable is the number of clover plants that survived (percentage survival).
Step 16
State TWO ways in which the scientists could have improved the reliability of the investigation.
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Repeat the investigation multiple times to ensure consistent results.
Set up more greenhouses at each temperature to increase sample size.
Step 17
Describe how the scientists calculated the percentage survival of clover plants.
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The percentage survival of clover plants was calculated by taking the number of plants that survived, dividing it by the original number (200), and then multiplying by 100.
Step 18
Explain if the hypothesis will be accepted or rejected.
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The hypothesis will be accepted because there are more clover plants in warmer areas which correlates with a higher percentage of survival.
Step 19
Explain ONE other way in which the survival rate of clover plants at different temperatures could be affected.
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Other factors, such as soil quality and water availability, could also affect the survival rate of clover plants at different temperatures.
Step 20
Explain how the mutation could affect the clover plants at later generations.
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The mutation may lead to some clover plants producing cyanide. Over successive generations, natural selection may favor plants that can survive better in their environments, thus potentially increasing the frequency of the cyanide-producing trait, impacting herbivore interactions and overall plant fitness.
