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In protein synthesis, the ribosome attaches to the genetic template (mRNA), which contains the genetic code from DNA. Free GCSE Biology notes and 10 FAQs.
Protein synthesis and gene variants is part of Additional inheritance patterns in GCSE Edexcel Higher Biology.
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In protein synthesis, the ribosome attaches to the genetic template (mRNA), which contains the genetic code from DNA. Free GCSE Biology notes and 10 FAQs.
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Use this lesson to stay inside Additional inheritance patterns while connecting the detail back to the wider Topic 3: Genetics topic.
Read the core explanations from Protein synthesis and gene variants before testing yourself from memory.
Your DNA contains the instructions for making every protein in your body. But how does a sequence of four letters (A, T, G, C) become a complex protein like haemoglobin or insulin?
Think of DNA as a recipe book written in a four-letter alphabet. Each 'word' in this recipe is exactly three letters long - we call this a triplet code. Just like changing one letter in a word changes its meaning, changing one base in the triplet changes which amino acid gets added to the protein.
Trap: Many students think one base codes for one amino acid. Actually, it takes three bases to code for each amino acid - that's why we call it the triplet code.
The order of bases in DNA directly controls the order of amino acids in the protein. Change the DNA sequence, and you change the protein. This is why genetic mutations can have such dramatic effects.
Picture a factory assembly line. The DNA sequence is like the instruction manual - it tells the workers (ribosomes) which parts (amino acids) to add and in what order. Get the instructions wrong, and the final product won't work properly.
Worked example: How DNA Sequence Determines Protein Structure
DNA sequence: ATG-CCG-GAA codes for which amino acid sequence?
Answer: Methionine-Proline-Glutamic acid
This direct relationship between DNA sequence and amino acid sequence explains why even small changes in DNA can have big effects. Change one base, and you might change one amino acid - which could change the entire protein's shape and function.
Ribosomes are the protein-making machines of the cell. They read the genetic template (like following a recipe) and assemble amino acids in the correct order to build proteins.
Think of ribosomes as highly skilled chefs. They read the recipe (genetic code), and carrier molecules act like waiters, bringing the right ingredients (amino acids) at exactly the right time. The chef adds each ingredient to the growing dish (protein chain) in the precise order specified.
Worked example: Protein Synthesis at the Ribosome
Describe how a ribosome makes a protein with 5 amino acids
Answer: Ribosome reads template → carriers bring amino acids → chain forms → protein released
Once the amino acid chain is complete, something remarkable happens - it folds up into a unique 3D shape. This folding isn't random; it's determined by the sequence of amino acids in the chain.
Imagine a long piece of string with different coloured beads (amino acids). Some beads are attracted to each other, some repel, and some are neutral. When you let go, the string automatically folds into a specific shape based on these attractions and repulsions.
This unique shape is crucial because it determines what job the protein can do. Enzymes need specific shapes to fit their substrates. Hormones need specific shapes to fit their receptors. Structural proteins like collagen need specific shapes to provide strength.
Trap: Students often think protein shape is random. Actually, the amino acid sequence completely determines the final 3D shape - change the sequence, change the shape, change the function.
Protein synthesis questions often test your understanding of the relationship between DNA, amino acids, and protein function. Here's how to tackle them like a pro.
Common exam mistakes include confusing the direction of information flow. Remember: DNA → amino acid sequence → protein shape → protein function. Information flows one way only.
Worked example: Answering a 6-Mark Protein Synthesis Question
Explain how the structure of DNA affects the proteins made in a cell. [6 marks]
Answer: A complete answer linking DNA structure → amino acid sequence → protein folding → specific function with examples
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Move to the related lessons or back to the topic page when you need the wider sequence before exam-style practice.
DNA codes for 20 amino acids using a triplet code, where three bases code for one amino acid. There are 64 possible combinations of three bases, so some amino acids are coded for by more than one triplet.
In protein synthesis, the ribosome attaches to the genetic template (mRNA), which contains the genetic code from DNA. Carrier molecules bring amino acids, peptide bonds form between adjacent amino acids, and the complete protein chain is released, ready for folding into its final 3D shape.
After the complete protein chain leaves the ribosome, it folds into a unique 3D shape determined by its sequence of amino acids. This final shape determines the protein's function, such as an enzyme needing a specific shape to fit its substrate.
Carrier molecules are molecules that transport specific amino acids to the ribosome during protein synthesis. Each carrier molecule recognises specific triplet codes and brings only one type of amino acid, so amino acids are added to the chain in the correct order.
To work out the amino acid sequence, split the DNA into triplets and look up the amino acid each triplet codes for. For example, ATG-CCG-GAA codes for methionine, proline and glutamic acid, joined in the same order as the DNA triplets.
Changing one DNA base changes the triplet, which might change one amino acid in the protein. Because the amino acid sequence determines how the chain folds, this could change the entire protein's 3D shape and function, which is why genetic mutations can have dramatic effects.
A ribosome reads a genetic template (mRNA) that contains the genetic code from DNA. Carrier molecules bring the right amino acids, and the ribosome joins them in the correct order to build the protein chain.
A ribosome adds amino acids in the order set by the triplets on its genetic template. Each carrier molecule recognises specific triplet codes and brings only one type of amino acid, so the amino acids join in the same order as the DNA triplets.
Examples of proteins made using DNA instructions include haemoglobin, insulin, enzymes, hormones and collagen. DNA contains the instructions for making every protein in the body, using a four-letter alphabet of bases.
Collagen is a structural protein whose specific shape provides strength and structural support. Like all proteins, its shape is determined by its amino acid sequence.