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1.3 Chromatin β Test 1
Q1. Constitutive heterochromatin is mostly composed of:β Repetitive DNA
Q2. Satellite DNA is NOT typically found in which chromosomal region?β Euchromatin
Q3. The basic structural unit of chromatin is the:β Nucleosome
Q4. The length of DNA wrapped in the nucleosome core particle is approximately:β 146 bp
Q5. Which core-histone modification is most associated with an ACTIVE (transcribed) chromatin state?β Acetylation
Q6. Which histone modification leads to ACTIVE transcription (open chromatin)?β H3-K9 acetylation
Q7. Which protein is NOT part of the nucleosome core particle?β H1
Q8. CpG islands in promoter regions must be in which state for the associated gene to be expressed?β Unmethylated
Q9. In nucleosomes, the eight core histones are arranged as an (H3)β(H4)β tetramer plus two H2AβH2B:β Dimers, left-handed wrap
Q10. Inter-nucleosomal DNA connecting adjacent nucleosomes is called:β Linker DNA
Q11. Histone deacetylase (HDAC) removes acetyl groups from which histone residue?β Lysine
Q12. Histone acetyltransferases and chromatin-remodelling complexes are recruited to genes mainly by:β Gene activator proteins
Q13. Which pair of histone modifications is associated with HETEROCHROMATIN (silencing)?β H3K9me3 and H3K27me3
Q14. Chromatin immunoprecipitation (ChIP) is used to determine:β Quantitative binding of a protein to chromatin (DNA) in vivo
Q15. Which covalent histone modification is NOT known to regulate gene expression?β Glycosylation
Q16. The covalent modification of histone tails affects chromatin because:β DNA is negatively charged and tail charge changes histoneβDNA affinity
Q17. Methylation-mediated transcriptional repression works by:β Recruiting proteins that promote histone deacetylation and further methylation
Q18. Which statement is the WRONG one?β Imprinted genes are controlled solely by histone acetylation of cis sites
Q19. siRNA functions by:β Forming a complex with RISC to degrade or block complementary mRNA
1.3 Chromatin β Test 2
Q20. The basic functional/structural unit of the eukaryotic genome (chromatin) is the:β Nucleosome
Q21. Venkatraman Ramakrishnan shared the Nobel Prize for the structure of the:β Ribosome
Q22. The nucleosome consists of:β 146 bp DNA wrapped around two copies each of H2A, H2B, H3 and H4
Q23. Which histones make up the nucleosome core (octamer)?β H2A, H2B, H3, H4
Q24. Locus control regions (LCRs) regulate gene clusters (e.g. globin) by which mechanisms? A) DNA looping to individual promoters B) recruiting chromatin-remodelling/histone-modifying enzymes and machineryβ A and B (both)
Q25. Inhibition of transcription by DNA methylation is most completely explained by:β Failure of TF binding plus recruitment of proteins that methylate and deacetylate histones
Q26. Most methylated cytosines in mammalian DNA occur in which context?β CpG dinucleotides
Q27. The packing ratio of DNA achieved by the 30-nm solenoid fibre is approximately:β 40
Q28. Which histone is the linker histone that binds linker DNA (not in the core)?β H1
Q29. DNA is highly viscous in solution mainly because of its:β Large length-to-diameter (axial) ratio
Q30. Which set of changes could de-repress a gene silenced by translocation to centromeric heterochromatin in S. pombe? (A) loss of HDAC Clr3; (C) loss of H3K9 methyltransferase Clr4; (D) loss of Dicerβ A, C and D
Q31. Which of the following is NOT true about the nucleosome core particle?β N-terminal histone tails are strictly ordered and rigid
Q32. Major portions of so-called 'junk DNA' in eukaryotes consist of:β Highly repetitive DNA and transposable elements
Q33. A loss-of-function screen isolating mutations that REACTIVATE a transgene silenced near the centromere would most likely recover a mutation in:β Histone H3K9 methyltransferase
Q34. Which statement about mRNA stability is correct? I) prokaryotic mRNAs have half-lives of minutes II) mRNA stability regulates gene expression III) poly(A) tails stabilise eukaryotic mRNAsβ I, II and III
Q35. The histone variant deposited at active promoters/regulatory regions to destabilise nucleosomes is:β H2A.Z
Q36. Heterochromatin protein 1 (HP1) recognises and binds which histone mark to spread heterochromatin?β H3K9me (methylated H3 lysine 9)