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Question 1
The table below shows the mRNA codons for different amino acids. For example, the codon GGG codes for the amino acid alanine. |
a) | Use information from the table to explain why the genetic code is described as degenerate.
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b) | Suggest the role of the mRNA codons UGA, UAG, and UAA.
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c) | Suggest one reason why the genetic code is often shown as mRNA codons rather than DNA triplets.
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d) | Describe how mRNA is formed by transcription of DNA in eukaryotic cells.
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Question 2
DNA sequences within the nucleus need to be transcribed into mRNA to synthesis proteins. |
a) | Describe the role of RNA polymerase in the process of transcription.
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b) | Some antibiotics are designed to interfere with the process of protein synthesis. The antibiotic actinomycin D works by binding to molecules of DNA directly, whereas the antibiotic α-amanitin works by binding to RNA polymerase. Explain how actinomycin D affects protein synthesis.
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c) | Explain how α-amanitin affects protein synthesis.
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d) | After transcription, mRNA molecules leave the nucleus and travel to the ribosomes. Describe the role of ribosomes in the the synthesis of proteins.
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Question 3
The table below shows the mRNA codons that result in different amino acids. For example, the codon UUC codes for the amino acid phenylalanine (Phe). |
a) | Describe why the genetic code is described as being universal.
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b) | A DNA base sequence that codes for a protein is shown below: GGT CAC GAA CCT TTA Use this sequence and the table above to work out the sequence of amino acids in this protein.
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c) | Use the information above to explain the nature of the genetic code.
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Question 4
The diagram below shows an example of a tRNA molecule. |
a) | Name structures labelled A and B in the diagram above.
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b) | tRNA molecules interact with ribosomes during the process of protein synthesis. Name the two types of molecule a ribosome is made up of.
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c) | Describe how one amino acid is added onto a growing polypeptide chain being synthesised by a ribosome.
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d) | DNA is found in both eukaryotic and prokaryotic cells. Describe the similarities and differences between the DNA found in these two types of cells.
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Question 5
Nucleic acids include biological molecules such as DNA and RNA. mRNA and tRNA are both types of RNA. |
a) | Describe two differences between the structure of mRNA and the structure of tRNA.
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b) | The table below shows the mRNA codons for some different amino acids. Below is the DNA template sequence used to determine the sequence of five amino acids. CAT CCT CCC CGC CAA Use information from the table above to give the amino acid sequence determined by this sequence.
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c) | DNA sequences code for proteins such as haemoglobin or digestive enzymes. Explain why the process of transcription is needed to synthesise these proteins.
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Question 6
The table below shows part of a pre-mRNA molecule transcribed from a section of DNA. |
a) | Complete the table with the base sequence of the DNA strand from which this pre-mRNA was synthesised.
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b) | What is the maximum number of amino acids this DNA sequence could code for?
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c) | Describe how a polypeptide is formed by translation of mRNA.
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Question 7
DNA is a biological molecule used to transmit genetic information from one generation to the next. |
a) | Describe the structure of a DNA molecule.
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b) | The genetic code uses four different nitrogenous bases. What is the maximum number of different DNA triplets that can be made using these four bases?
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c) | DNA is copied during the process of DNA replication. DNA is also used in the process of transcription to form mRNA. Describe the similarities and the differences between the processes of DNA replication and transcription.
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