Which structures give a 'beads on a string' appearance when chromosomes are viewed under an electron microscope?
Correct answer: C. Nucleosomes
- A. Genes
- B. Nucleotides
- C. Nucleosomes
- D. Base pairs
Explanation
Nucleosomes appear as 'beads on a string' in the chromosomes when viewed under an electron microscope. The beads in 'beads on a string' arrangement are complexes of histones and DNA. The beads, plus the connecting DNA that leads to the next bead, form the nucleosome. A nucleosome is the fundamental unit of organisation on which the higher-order packaging of chromatin is built. The bead of each nucleosome contains eight histone molecules, in which two copies each of H2A, H2B, H3, and H4 are found.
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About Cell Structure and Function
Animal, plant, prokaryotic and eukaryotic cells are compared through their membranes, cell walls, nuclei and cytoplasmic organelles. The work includes the structures and functions of mitochondria, chloroplasts, ribosomes, endoplasmic reticulum, Golgi apparatus and lysosomes, as well as chromosome organization and the distinction between chromatin and chromosomes.
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