A student analyzing actively dividing cells under the microscope finds that each daughter cell contains half the number of chromosomes as the parent cell. Given this, these cells most likely contain all of the following EXCEPT:

Question

A student analyzing actively dividing cells under the microscope finds that each daughter cell contains half the number of chromosomes as the parent cell.  Given this, these cells most likely contain all of the following EXCEPT:

Quizplus · Accepted Answer

11ecba2d_1010_96d3_a3bf_abb6a6289f82_MD0008_00 Eukaryotic cells can be distinguished from other cells because they have certain unique characteristics. For example, a eukaryotic cell divides via mitosis or meiosis. Although mitosis produces daughter cells identical to the parent cell, meiosis yields four daughter cells, each with half the genetic material of the parent cell. In the given scenario, the student observed actively dividing cells that were producing daughter cells with half the number of chromosomes as the parent cell. Accordingly, this student was microscopically analyzing eukaryotic cells undergoing meiosis. As another example, membrane-bound organelles that comprise what is known as the endomembrane system are unique to eukaryotic cells. Because these organelles are filled with fluid, they are enclosed by a plasma membrane to separate their interior from the surrounding cytoplasm. The following are examples of membrane-bound organelles: Peroxisomes are small organelles that help maintain the oxidation state of the cell by facilitating oxidation-reduction reactions to remove peroxides (chemicals harmful to the cell) (Choice A). The nucleus is the storage site for DNA (ie, linear chromosomes) and where replication and transcription (but not translation) occur. Because translation takes place in the cytoplasm, the mRNA molecule resulting from transcription must exit the nucleus. Consequently, nuclear membrane channels known as nuclear pores facilitate the passage of mRNA out of the nucleus and into the cytoplasm (Choice B). Nuclear pores, which also regulate the passage of certain proteins in and out of the nucleus, allow the compartmentalization of molecular processes. Eukaryotic cells also have more solid (ie, not fluid-filled) structures that are not membrane-bound (eg, ribosomes, cytoskeletal filaments, centrosomes). For instance, the filaments that comprise the eukaryotic cytoskeleton include microtubules (Choice D) along with actin and intermediate filaments. The cytoskeleton supports the shape and internal structure of the cell, and provides tracts for the transport of cellular cargo by motor proteins. (Choice C) Single-stranded genomes can be found in certain viruses. However, eukaryotic cells do not possess this kind of genomic material and instead have double-stranded genomes. Educational objective: Eukaryotic cells can be distinguished by their unique characteristics. For example, they have a genome with multiple linear chromosomes (double-stranded DNA), they use meiosis as one mechanism of cell division (sexual reproduction), and they have membrane-bound organelles.

A Student Analyzing Actively Dividing Cells Under the Microscope Finds