Higher Tier: sequence, protein shape and gene expression
הוצג| English | משמעות |
|---|---|
| protein synthesis/ˈprəʊtiːn ˈsɪnθəsɪs/ | סינתזת חלבון |
| gene expression/dʒiːn ekˈspreʃn/ | ביטוי גן |
What would explain this observation?
- Higher Tier: A DNA change can alter a protein’s shape, leave its function unchanged, or change how much protein is made. These are different causal routes.
Build the model
- Complementary DNA strands pair A with T and C with G.
- Proteins are synthesised on ribosomes according to a template.
- Carrier molecules bring specific amino acids, which join in the correct order.
- The completed chain folds into a unique shape suited to its function, such as an enzyme, a hormone or a structural protein including collagen.
- protein synthesis 蛋白质合成: Assembly of an amino-acid chain on a ribosome according to a template.
- gene expression 基因表达: Use of genetic information to produce a functional product.
Which account fits a non-coding regulatory variant?
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Non-coding DNA does not code for protein, but regulatory sections can switch genes on or off, so a variant there can change expression. It cannot change amino acids directly, and "non-coding" is not "functionless".
Match each technical term to its precise meaning.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- A change in coding DNA can change the amino-acid sequence and therefore folding.
- An enzyme’s active site may no longer fit its substrate, or a structural protein may lose strength.
- Most mutations do not change the protein, or change it too little to alter its appearance or function.
- Non-coding DNA can control whether genes are switched on or off; variants there may affect expression without changing the coded amino-acid sequence.
In the lab: Use supplied short sequences and an explicit classroom code key. First distinguish a coding-region change from an expression-control change, then trace only the consequence supported by the prompt. Detailed structures of mRNA, tRNA, amino acids and proteins are not required. Model substitutions or insertions with cards rather than treating all mutations as harmful.
Which two habits make the investigation or model in this case more defensible?
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
Stating the conditions and assumptions lets others repeat the work exactly, and recording the supporting evidence lets them check the conclusion. Hiding disagreeing results removes the evidence that could challenge a wrong conclusion, and one measurement can never establish a wider claim.
Work from known quantities
- Known: a supplied strand is A C G T.
- Its complementary sequence is T G C A in the paired display.
- In a separate fictional sample, 4 of 80 observed variants alter the measured phenotype: 4/80×100 = 5%.
- These supplied frequencies do not establish a universal mutation rate or prove the remaining variants have no effect in every environment.
Your turn: Five of 100 variants in a fictional study alter the measured phenotype. Find the percentage.
Five of 100 variants in a fictional study alter the measured phenotype. Find the percentage.
רמת קושי 2/5 · 140 מטבעות + בונוס קטן בהשלמה הראשונה היום
The result is 5 %. Known: 5 of 100 variants alter the phenotype. Use percentage = altering / total x 100. Percentage = 5/100 x 100 = 5%. A supplied frequency is not a universal mutation rate.
Check the conclusion and its limits
- DNA does not assemble the protein directly inside the nucleus in this account: synthesis takes place on ribosomes.
- A changed sequence does not automatically create a useful or harmful phenotype.
- Non-coding means not coding a protein, not having no function.
Not true: Every mutation changes protein shape and causes disease. Most mutations are neutral - in non-coding regions or synonymous codons - and some are beneficial. Only a minority alter a protein harmfully, so mutation does not imply disease.
- Complementary DNA strands pair A with T and C with G.
- A change in coding DNA can change the amino-acid sequence and therefore folding.
- Watch for: DNA does not assemble the protein directly inside the nucleus in this account: synthesis takes place on ribosomes.
Every mutation changes protein shape and causes disease.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
Most mutations are neutral - in non-coding regions or synonymous codons - and some are beneficial. Only a minority alter a protein harmfully, so mutation does not imply disease.
Assembly of an amino-acid chain on a ribosome according to a template: write the technical term.
רמת קושי 1/5 · 100 מטבעות + בונוס קטן בהשלמה הראשונה היום
protein synthesis means Assembly of an amino-acid chain on a ribosome according to a template.