Multiple Choice
In eukaryotic cells, why must DNA be tightly packed into chromatin and higher-order chromosome structures?
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7. DNA and Chromosome Structure
Eukaryotic Chromosome Structure
Multiple Choice
Which of the following is the correct order of chromosomal packaging levels?
A
Nucleosome, 250nm fiber, 30nm fiber, chromosome
B
250nm fiber, 30nm fiber, nucleosome, chromosome
C
Nucleosome, 30nm fiber, 250nm fiber, chromosome
D
Nucleosome, 30nm fiber, chromosome, 250nm fiber
Verified step by step guidance1
Begin by understanding the basic unit of chromosomal packaging: the nucleosome. A nucleosome consists of DNA wrapped around histone proteins.
Next, recognize that nucleosomes coil to form a more compact structure known as the 30nm fiber. This is the second level of chromosomal packaging.
The 30nm fiber further folds and loops to form the 250nm fiber, which is a higher-order structure providing additional compaction.
Finally, the 250nm fiber is organized into the most condensed form, the chromosome, which is visible during cell division.
By following these steps, you can determine that the correct order of chromosomal packaging is: Nucleosome, 30nm fiber, 250nm fiber, chromosome.
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