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3.5 Homology, Orthology & Paralogy — Test 1
Q1. Two sequences are said to be homologous when they:✓ Share a common evolutionary ancestor
Q2. A common misconception corrected in bioinformatics is that:✓ Sequences are either homologous or not — one cannot say they are 'x% homologous'
Q3. Orthologues are homologous sequences that diverged as a result of:✓ A speciation event
Q4. Paralogues are homologous sequences that arose by:✓ Gene duplication within a genome
Q5. Sequence similarity is best described as:✓ The measurable evidence often used to infer homology
Q6. Orthologues are especially useful in bioinformatics because they:✓ Usually retain the same function, allowing functional annotation transfer between species
Q7. Paralogues, unlike orthologues, are more likely to:✓ Diverge and acquire new or specialised functions
Q8. Homologous sequences are expected to share, to some degree, a similar:✓ Three-dimensional structure and often function
Q9. Xenologues are homologous genes whose relationship results from:✓ Horizontal (lateral) gene transfer
Q10. Similar features that arise by convergent evolution (not common ancestry) are termed:✓ Analogous (not homologous)
Q11. A group of homologous genes related by descent is called a:✓ Gene family
Q12. To say two genes are '40% identical' rather than '40% homologous' is correct because:✓ Identity is a measurable percentage, whereas homology is a yes/no relationship
Q13. Databases such as COG and OrthoDB are used to catalogue:✓ Orthologous groups of genes across species
Q14. The fact that structure is more conserved than sequence means that:✓ Proteins with low sequence identity can still share the same fold
Q15. Inferring the function of an uncharacterised gene from its well-studied orthologue is reliable mainly because orthologues:✓ Tend to conserve the ancestral function
Q16. Within a single human genome, two related genes arising from an ancient duplication are:✓ Paralogues
Q17. High statistical significance of a sequence match increases confidence that the similarity reflects:✓ True homology rather than chance
Q18. Orthologues and paralogues are both types of:✓ Homologues
Q19. A practical reason to distinguish orthologues from paralogues is that:✓ Functional inference is generally safer from orthologues than paralogues
Q20. Match each term with its description and select the correct option.✓ A-iii, B-ii, C-iv, D-i