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
(... show full transcript
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), a single-stranded nucleic acid that carries genetic information from DNA to the ribosomes for protein synthesis.
Step 2
Identify: (a) Part X
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Answer
Part X is identified as a nitrogenous base.
Step 3
Identify: (b) Sugar Y
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Answer
Sugar Y is identified as ribose.
Step 4
Describe the process of transcription.
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Answer
Transcription is the process by which the double-stranded DNA molecule unwinds and unzips. The hydrogen bonds break, allowing one strand to be used as a template to form mRNA. Free RNA nucleotides from the nucleoplasm align with their complementary bases on the DNA strand (A with U, and C with G), facilitated by enzymes. The mRNA then detaches and is processed before being transported to the ribosomes.
Step 5
Give THREE sources of genetic variation in a species.
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Answer
Crossing over during meiosis.
Random arrangements of chromosomes during meiosis.
Random fertilization, which combines genes from two parents.
Step 6
Differentiate between continuous variation and discontinuous variation.
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Continuous variation refers to traits that show a range of phenotypes across a continuum (e.g., height), while discontinuous variation refers to traits that fall into separate categories without intermediate forms (e.g., blood type).
Step 7
Give the: (a) DNA triplet for the third amino acid from the left in the sequence for protein 2.
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The DNA triplet for the third amino acid from the left in the sequence for protein 2 is ACC.
Step 8
Give the: (b) Codon for lysine.
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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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1 gene is involved in coding for protein 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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198 RNA nucleotides are involved since each amino acid is encoded by a triplet of nucleotides and there are 66 amino acids in protein 1.
Step 12
How many of EACH of the following is involved in the formation of this protein? (c) Codons
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66 codons are involved as each triplet corresponds to one amino acid.
Step 13
Describe how the mutation caused a change in the structure of the protein.
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The mutation changed one of the base triplets on the DNA, resulting in a different codon sequence from ACG to ACC. Consequently, this altered the amino acid sequence from cysteine (which is coded by the original triplet ACG) to tryptophan (coded by the new triplet ACC), thus changing the structure and possibly the function of the resulting protein.
Step 14
State the: (a) Independent variable
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The independent variable is the temperature of the environment where the clover plants were grown.
Step 15
State the: (b) Dependent variable
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The dependent variable is the number of clover plants that survived, measured as a percentage.
Step 16
State TWO ways in which the scientists could have improved the reliability of the investigation.
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Conduct the investigation in more greenhouses at each temperature.
Use a larger sample size of clover plants.
Step 17
Describe how the scientists calculated the percentage survival of clover plants.
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The scientists counted the number of surviving clover plants and divided that number by the original number of plants (200), then multiplied by 100 to get the percentage survival.
Step 18
Explain if the hypothesis will be accepted or rejected.
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The hypothesis will be accepted because the data shows that there are more clover plants surviving in the higher temperature conditions (25 °C) compared to the lower temperature (5 °C).
Step 19
Explain ONE other way in which the survival rate of clover plants at different temperatures could be affected.
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Another factor that could influence the survival rate is the availability of water, as insufficient water can lead to higher mortality rates among the plants.
Step 20
Refer to Darwin's theory of natural selection and explain how the mutation could affect the clover plants at later generations.
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Darwin's theory of natural selection posits that individuals better adapted to their environment tend to survive and reproduce. The mutation causing cyanide production may allow some clover plants to survive herbivory; thus, they may reproduce, passing on the trait to future generations, while plants without the mutation may face higher predation and consequently lower reproductive success.
