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
According to the table, how many codons code for phenylalanine?
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Answer
From the table provided, there are two mRNA codons that code for phenylalanine: UUC and UUU. Therefore, the answer is 2.
Step 2
What is the anticodon for glutamic acid?
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Answer
The mRNA codon for glutamic acid (GAG) pairs with the tRNA anticodon CUC.
Step 3
Give the:
(a) DNA base triplet for the LAST codon on this section of mRNA
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Answer
The last codon in the mRNA sequence is ACC. The corresponding DNA triplet would be TGG.
Step 4
(b) FIRST amino acid coded for by this section of mRNA
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Answer
The first amino acid coded for by this mRNA sequence is Aspartate, represented by the codon GAU.
Step 5
Describe the mutation that occurred.
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The mutation involved a change where the fourth codon AGC was altered, resulting in a mutation of C being replaced by U, changing the codon to AUG.
Step 6
(b) Explain the effect that the mutation described in QUESTION 2.1.4(a) will have on the resulting protein.
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Answer
This mutation will likely not change the resulting protein because both AGC and UGC code for the same amino acid, Serine, thus no effect on the protein function is expected.
Step 7
Name and describe the process occurring in the nucleus which results in the formation of an mRNA molecule.
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The process occurring is called transcription. During transcription, the enzyme RNA polymerase synthesizes mRNA from a DNA template by unwinding the DNA double helix and assembling a complementary RNA strand.
Step 8
Define a population.
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A population is a group of organisms of the same species that can interbreed and occupy a defined area at a specific time.
Step 9
Other than mutations, give THREE causes of variation in a population.
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Crossing over during meiosis
Random arrangement of chromosomes
Random fertilization
Step 10
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 caused by the mutation survived better in the environmental conditions, leading to natural selection favoring these traits.
Step 11
Explain what effect the process above has on the biodiversity in this ecosystem.
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The biodiversity increased as two new species emerged, which increases genetic variability and ecosystem resilience.
Step 12
Describe what can be done to confirm that the squirrels belong to two different biological species.
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Conduct DNA tests of both species and compare the genetic material to see if they have sufficient genetic differentiation, indicating they are distinct species.
Step 13
Give the:
(a) Phenotype of Senzo
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Senzo's phenotype is Colour-blind male.
Step 14
(b) Genotype of Thuli.
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The genotype of Thuli is X^dX^.
Step 15
Describe how Linda inherited colour-blindness.
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Linda inherited one recessive allele (X^d) from her father and one normal allele (X) from her mother.
Step 16
Explain why there are generally more males than females with colour-blindness in a population.
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Males have only one X chromosome, so if they inherit the X^d allele, they will express the colour-blind trait. In contrast, females need two copies of the X^d allele to be colour-blind.
Step 17
Use a genetic cross to show the possible genotypes and phenotypes of their children.
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P1: Normal female (X^X) x Normal male (XY);
Gametes: X or X^ (from female) and X or Y (from male);
