How genes make proteins Cambridge IGCSE Biology revision
Not started
Learn it
In plain words
A gene is a recipe, and the dish is a protein. But the recipe book (the DNA) can't leave the nucleus, and proteins are made outside it. So the cell makes a copy of the one recipe it needs, sends that out, and builds the protein by reading it three letters at a time.
Three things to know
- The order of bases in a gene decides the order of amino acids in a protein, and so the protein's shape and what it does.
- A copy of the gene is made as mRNA in the nucleus. The mRNA moves out to a ribosome in the cytoplasm.
- The ribosome reads the mRNA and joins amino acids together in the right order to make the protein. Every body cell has the same genes, but each type of cell uses only the ones it needs.
Tips and tricks
- DNA stays in the nucleus; mRNA carries the message out to the ribosomes.
- A different base sequence means a different amino acid sequence, which means a different protein. That chain explains mutations.
It lands in your notebook with its questions as flashcards.
How genes make proteins: 5 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
Where in the cell are proteins made?
Ribosomes are in the cytoplasm.
What carries a copy of a gene from the nucleus to a ribosome?
DNA itself stays in the nucleus.
What decides the order of amino acids in a protein?
The base sequence is a code.
What are proteins made of?
They are joined in a chain in a particular order.
Why do different types of cell make different proteins?
All cells have the same genes, but not all are switched on.
Quiz
5 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 7 marks. Write your answers on paper, then check them.
How genes make proteins
Cambridge IGCSE Biology 0610 · 7 marks · papermunch.org
Name ______________________________ Date ______________
Describe how a protein is made from the information in a gene.[3]
Show answerHide answer
A copy of the gene is made as mRNA in the nucleus. The mRNA moves to a ribosome in the cytoplasm. The ribosome uses the sequence of bases to join amino acids in the correct order.
Explain why a change in the base sequence of a gene can change a protein.[2]
Show answerHide answer
The base sequence determines the sequence of amino acids. A different sequence of amino acids gives a protein with a different shape, which may not work in the same way.
All body cells contain the same genes. Explain why a muscle cell is different from a nerve cell.[2]
Show answerHide answer
Only some genes are expressed (switched on) in each type of cell, so each makes a different set of proteins.
Answers: How genes make proteins
- 1. A copy of the gene is made as mRNA in the nucleus. The mRNA moves to a ribosome in the cytoplasm. The ribosome uses the sequence of bases to join amino acids in the correct order.
- 2. The base sequence determines the sequence of amino acids. A different sequence of amino acids gives a protein with a different shape, which may not work in the same way.
- 3. Only some genes are expressed (switched on) in each type of cell, so each makes a different set of proteins.