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DNA is transcribed and translated during protein synthesis - Edexcel - GCSE Biology - Question 6 - 2018 - Paper 1
Question 6
DNA is transcribed and translated during protein synthesis. Describe how DNA is transcribed. (3) Which of the statements about gene mutations are true? 1. Gene m... show full transcript
Worked Solution & Example Answer:DNA is transcribed and translated during protein synthesis - Edexcel - GCSE Biology - Question 6 - 2018 - Paper 1
Step 1
Describe how DNA is transcribed.
Answer
DNA transcription is the process in which the genetic information from DNA is copied to messenger RNA (mRNA). This occurs in several steps:
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DNA Unzipping: The DNA double helix unwinds and unzips at the region where the gene to be transcribed is located. This process is facilitated by enzymes that break the hydrogen bonds between the complementary base pairs.
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Base Pairing: Free RNA nucleotides then pair with the exposed DNA bases, following the base-pairing rules—adenine (A) with uracil (U) in RNA (replacing thymine, T), and cytosine (C) with guanine (G).
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mRNA Synthesis: As RNA polymerase moves along the DNA strand, it catalyzes the formation of the RNA molecule by linking the RNA nucleotides together, forming a single strand of mRNA.
After transcription, the newly formed mRNA strand detaches from the DNA and exits the nucleus, where it will later be translated into a protein.
Step 2
Step 3
Explain how a gene mutation can change the function of a protein.
Answer
A gene mutation can alter the sequence of amino acids in a protein, which in turn can change its structure and function.
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Types of Mutations: Mutations can be categorized as:
- Missense Mutations: These cause a change in a single amino acid, potentially altering the protein's functionality.
- Nonsense Mutations: These introduce a premature stop codon, resulting in a truncated protein that is usually nonfunctional.
- Frameshift Mutations: These occur due to insertions or deletions of bases, which can drastically change the protein's amino acid sequence downstream.
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Implications: Changes to the protein structure can affect its ability to bind substrates, catalyze reactions, or interact with other molecules, which may lead to loss of function or gain of new, possibly harmful functions, affecting cellular mechanisms and overall organism health.