9. What is removed during post transcriptional modification? a) Introns b) Exons c) 5'Cap d) Mutations 10. How does a single eukaryotic cell contain an entire genome:worth of DNA? a) Chromatin fibres b) Histones c) Supercoiling d) All of the above

9. **a) Introns**<br /><br />Introns are non-coding sequences within a gene. During post-transcriptional modification, they are removed from the pre-mRNA molecule through a process called splicing. Exons, the coding sequences, are joined together to form the mature mRNA.<br /><br />10. **d) All of the above**<br /><br />Eukaryotic cells manage to pack an enormous amount of DNA into a tiny nucleus through several mechanisms:<br /><br />* **Chromatin fibres:** DNA is wrapped around histone proteins to form chromatin fibres, which are more compact than naked DNA.<br />* **Histones:** These proteins act as spools around which DNA winds, facilitating the first level of DNA compaction.<br />* **Supercoiling:** Further coiling and looping of the chromatin fibres compresses the DNA even more, allowing it to fit within the nucleus.<br />