2.1 The sequence of amino acids in a protein molecule is coded for by DNA and RNA - NSC Life Sciences - Question 2 - 2017 - Paper 2
Question 2
2.1 The sequence of amino acids in a protein molecule is coded for by DNA and RNA. The table below shows some mRNA codons and the corresponding amino acids.
mRNA CO... show full transcript
Worked Solution & Example Answer:2.1 The sequence of amino acids in a protein molecule is coded for by DNA and RNA - NSC Life Sciences - Question 2 - 2017 - Paper 2
Step 1
2.1.1 According to the table, how many codons code for phenylalanine?
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Answer
According to the table, there are 2 codons that code for phenylalanine, which are UUC and UUU.
Step 2
2.1.2 What is the anticodon for glutamic acid?
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Answer
The anticodon for glutamic acid (GAG) is CUC.
Step 3
2.1.3 (a) DNA base triplet for the LAST codon on this section of mRNA
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The last codon in the given mRNA sequence is ACC, so the corresponding DNA base triplet is TGG.
Step 4
2.1.3 (b) FIRST amino acid coded for by this section of mRNA
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The first codon of the mRNA sequence is GAU, which codes for the amino acid aspartate.
Step 5
2.1.4 (a) Describe the mutation that occurred.
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The mutation resulted in the fourth codon changing from AGC to AGU. This can be defined as a substitution mutation where one base pair in the mRNA has been altered.
Step 6
2.1.4 (b) Explain the effect that the mutation described in QUESTION 2.1.4(a) will have on the resulting protein.
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The mutation leads to the coding of the same amino acid, serine, for both AGC and AGU codons. Therefore, the mutation does not affect the protein structure, as the resulting protein would be identical.
Step 7
2.1.5 Name and describe the process occurring in the nucleus which results in the formation of an mRNA molecule.
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The process is called transcription. During transcription, the DNA double helix unwinds, and one strand serves as a template for the synthesis of mRNA. RNA polymerase facilitates this process, and the complementary RNA nucleotides are added to form the mRNA strand.
Step 8
2.2.1 Define a population.
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A population is defined as a group of organisms of the same species that can interbreed and occupy a specific area at a given time.
Step 9
2.2.2 Other than mutations, give THREE causes of variation in a population.
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Three causes of variation include:
Crossing over during meiosis
Random arrangement of chromosomes during metaphase
Random mating among individuals.
Step 10
2.2.3 Explain why there were eventually more squirrels with the mutation on one side of the river.
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The squirrels with favourable characteristics due to the mutation survived and reproduced more effectively than those without it. This resulted in a greater population of mutant squirrels on that side, driven by natural selection.
Step 11
2.2.4 Explain what effect the process above has on the biodiversity in this ecosystem.
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The process of speciation has led to an increase in biodiversity since two separate species of squirrels now occupy the ecosystem, leading to increased variety in gene pools and ecological roles.
Step 12
2.2.5 Describe what can be done to confirm that the squirrels belong to two different biological species.
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To confirm that the squirrels belong to two different biological species, researchers can conduct DNA tests of both species to compare genetic differences, ensuring they do not interbreed and can produce fertile offspring.
Step 13
2.3.1 (a) Give the phenotype of Senzo.
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The phenotype of Senzo is colour-blind male.
Step 14
2.3.1 (b) Give the genotype of Thuli.
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The genotype of Thuli is X^F X^d.
Step 15
2.3.2 Describe how Linda inherited colour-blindness.
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Linda inherited colour-blindness as she received one X chromosome carrying the colour-blind allele (X^d) from her father and one X chromosome (either normal or colour-blind) from her mother, making her genotype either X^F X^d or X^d X^d.
Step 16
2.3.3 Explain why there are generally more males than females with colour-blindness in a population.
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Males typically have a single X chromosome, so if they inherit the X chromosome carrying the recessive allele (X^d), they will express colour-blindness. Females, however, have two X chromosomes and require two copies of the allele to be colour-blind, which is why males are generally affected more frequently.
Step 17
2.3.4 Use a genetic cross to show the possible genotypes and phenotypes of their children.
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In a genetic cross between a normal male (X^F Y) and Molly (X^d X^d):
Parent Genotype
X^d
X^d
X^F
X^F X^d
X^F X^d
Y
X^d Y
X^d Y
The possible genotypes are X^F X^d (normal female), X^F X^d (normal female), X^d Y (colour-blind male), and X^d Y (colour-blind male). The phenotypes would thus show normal females and colour-blind males.
