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6 (a) DNA is transcribed and translated during protein synthesis - Edexcel - GCSE Biology - Question 6 - 2018 - Paper 1
Question 6
6 (a) DNA is transcribed and translated during protein synthesis. Describe how DNA is transcribed. (b) Which of the statements about gene mutations are true? 1. Gen... show full transcript
Worked Solution & Example Answer:6 (a) 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 by which the genetic information in DNA is converted into messenger RNA (mRNA). This process involves the following steps:
- Unwinding of DNA: The DNA double helix strands are separated by the enzyme helicase, allowing access to the template strand.
- Base Pairing: RNA nucleotides pair with the exposed DNA bases, following the base pairing rules: adenine (A) pairs with uracil (U) in RNA, while cytosine (C) pairs with guanine (G).
- Formation of mRNA: The enzyme RNA polymerase catalyzes the addition of RNA nucleotides to form a single strand of mRNA.
- Capping and Editing: The mRNA undergoes processing which includes the addition of a 5' cap and a poly-A tail, and the splicing of introns to form a mature mRNA molecule ready for translation.
Step 2
Step 3
Explain how a gene mutation can change the function of a protein.
Answer
Gene mutations can alter the sequence of amino acids in a protein, potentially changing its structure and function. For example:
- Missense Mutations: A single nucleotide change may result in the substitution of one amino acid for another in the protein sequence, which can affect the protein's stability and functionality.
- Nonsense Mutations: A mutation that creates a premature stop codon can lead to a truncated protein that may be nonfunctional.
- Frameshift Mutations: Insertions or deletions of nucleotides can shift the reading frame during translation, leading to completely different and typically nonfunctional proteins. These changes can result in various diseases or disorders depending on the protein's role in the body.