- Key words
- Clean sweep - quick revision through the whole topic
- Structured question about tRNA
- Model answer
- Revision summary list for topic 7.3 Translation
- Revision mindmaps
- Review questions
- 7.3 Translation HL 1/1
This topic includes some interesting and difficult details about the synthesis of proteins on ribosomes. While these aspects are difficult they do not need to understood in great detail. One challenge in this topic is to get the right balance between understanding details and making simple notes.
Key words
Learn and test your biological vocabulary for 7.3 Translation using these flashcards.
Clean sweep - quick revision through the whole topic
These slides summarise the essential understanding and skills in this topic.
They contain short explanations in text and images - good revision for all students.
Read the slides and look up any words or details you find difficult to understand.
Structured question about tRNA
Understanding the structure and function of tRNA is an important skill from this topic.
Answer the question below on a piece of paper, then check your answer against the model answer below.
Outline the structure of a tRNA molecule and how its two binding sites are used during translation.. [3]
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Click the + icon to see a model answer.
Revision summary list for topic 7.3 Translation
DNA structure
- Part of DNA supercoiling are structures called Nucleosomes.
- DNA structure gives a clue to the mechanism of DNA replication.
- Non-coding regions of DNA have other important functions, limited to regulators of gene expression, introns, telomeres and genes for tRNAs.
DNA replication (in prokaryotes only)
- DNA polymerase enzymes can only add nucleotides to the 3’ end of a primer.
- Continuous DNA replication occurs on the leading strand and discontinuous on the lagging strand.
- A complex group of enzymes do DNA replication including; helicase, DNA gyrase, single strand binding proteins, DNA primase and DNA polymerases I and III.
Crossing over
- DNA replication makes a second chromatid in each chromosome in interphase before meiosis.
- Crossing over exchanges pieces of DNA between non-sister homologous chromatids and forms new combinations of alleles on the chromosomes formed in meiosis.
Skills (can you ...)
- Say how Rosalind Franklin’s and Maurice Wilkins’ X-ray diffraction work gave insights into the structure of DNA.
- Know that the Sanger method of base sequencing uses nucleotides containing dideoxyribonucleic acid (DNA with deoxyribose missing 2 oxygen molecules) that stops DNA replication at a specific base.
It allows sequencing using fluorescent markers and computers. (Sanger chain termination. Video here) - Say that in DNA profiling Tandem repeats are used as these vary greatly from person to person.
- Analyse results of the Hershey and Chase experiment providing evidence that DNA is the genetic material. .Graphic
- Use of molecular visualization software to analyse the association between protein and DNA within a nucleosome
Revision mindmaps
These diagram summaries cover the main details of topic 7.3 Translation.
Study them and draw your own list or concept map, from memory if you can.
Review questions
This quiz contains multiple choice questions covering the understandings and skills in this topic.
START QUIZ!
Which of the following best describes initiation of translation?
Initiation is the assembly of the components (large and small ribosome subunits, mRNA and tRNA molecules) that carry out the process.
The diagram shows a ribosome during the elongation stage of transcription.
In which order does tRNA bind to the different sites on the mRNA molecule ?
Synthesis of the polypeptide involves a repeated cycle on a ribosome where tRNA binds to the A (aminoacyl), P (peptidyl) and E (exit) sites in turn. Polypeptide molecule is produced.(Note: examples of start and stop codons are not needed)
Which description best describes termination of translation?
Termination of translation is followed by disassembly of the components.
One of the three stop codons enters the A site. No tRNA molecules bind to these codons so the polypeptide and tRNA in the P site are released into the cytoplasm and the small and large subunits of the ribosome dissassemble
In eukaryote cells ribosomes are found bound to membranes in rER or free in the cytoplasm.
Outline the role of free ribosomes.
Bound ribosomes synthesize proteins primarily for secretion or for use in lysosomes and membranes.
Free ribosomes produce polypeptides and thus proteins which remain in the cytoplasm.
Prokaryotes don't have a nuclear membrane. How does this change the proocess of translation, compared to eukaryotes?
Translation can occur immediately after transcription in prokaryotes due to the absence of a nuclear membrane.
Which of the following statements is the best description of "Primary structure of a protein"?
The sequence and number of amino acids in the polypeptide is the primary structure.
There are three structures, shown in this ribbon diagram of a protein?
What level of protein structure are they and what are they called?
The folding of a protein backbone into a 3D arangement of alpha helices and beta-pleated sheets is which level of protein structure?
The tertiary structure is the further folding of the polypeptide stabilised by interactions between R groups.
(Polar and non-polar amino acids are relevant to the bonds formed between R groups.)
How can you tell if a protein has quaternary structure?
The quaternary structure exists in proteins with more than one polypeptide chain. and may involve the binding of a prosthetic group to form a conjugated protein.
Revision fun activity
Everyone needs a bit of fun while they revise. Try this Translation 7.3 card match game.
Can you reach the leader board?