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Question Video: Identifying the Parts of the Nucleus in an Electron Micrograph Biology

The micrograph shows a cell viewed under a transmission electron microscope. A circular nucleus is visible. Which of the following is not part of the structure of a nucleus? [A] Nuclear envelope [B] Nuclear pores [C] Nucleoplasm [D] Nuclear cristae [E] Nucleolus

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Video Transcript

The micrograph shows a cell viewed under a transmission electron microscope. A circular nucleus is visible. Which of the following is not part of the structure of a nucleus? (A) Nuclear envelope, (B) nuclear pores, (C) nucleoplasm, (D) nuclear cristae, or (E) nucleolus.

In eukaryotic cells, the majority of the genetic material, or DNA, is contained in the nucleus. The DNA is found in long strands wrapped around proteins. And together, these structures are known as chromatin. The nucleus also controls the expression of DNA and therefore has unique structural features that allow it to store, replicate, and transfer genetic information.

The nuclear membrane is known as the nuclear envelope. It is a double membrane that has special openings called nuclear pores. The pores allow some molecules, such as ribosomal RNA and subunits of ribosomes, to pass between the cytoplasm of the cell and the interior of the nucleus. So, we know that answers (A) and (B) can be ruled out because they both describe structures of the nucleus.

In the interior of the nucleus is a liquid matrix, called the nucleoplasm. It is similar to the cytoplasm within the cell. Suspended within the nucleoplasm is the nucleolus, a dense cluster of proteins and genetic material that produces ribosomes. Let’s go ahead and eliminate answers (C) and (E), now that we know that the nucleoplasm and nucleolus are both structures found within the nucleus.

Cristae are not found in the nucleus but rather are the folds of the inner membrane of mitochondria. So, the correct answer is (D). Nuclear cristae are not a structure of the nucleus.

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