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Chapter 2: Problem 3

What role do the following cellular components play in the storage, expression, or transmission of genetic information: chromatin, (b) nucleolus, (c) ribosome, (d) mitochondrion, centriole, (f) centromere?

Short Answer

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Question: List the roles of the following cellular components in terms of storage, expression, or transmission of genetic information: (a) Chromatin, (b) Nucleolus, (c) Ribosome, (d) Mitochondrion, (e) Centriole, and (f) Centromere. Answer: (a) Chromatin: Packages DNA and regulates gene expression. (b) Nucleolus: Synthesizes ribosomal RNA (rRNA), which is crucial for protein synthesis. (c) Ribosome: Translates genetic information from mRNA into protein synthesis. (d) Mitochondrion: Has its own genetic material and replication process, separate from the nuclear genome. (e) Centriole: Ensures the accurate distribution of genetic material during cell division, although it does not directly store or express genetic information. (f) Centromere: Essential for proper chromosome segregation during cell division, ensuring accurate transmission of genetic material.

Step by step solution

01

(a) Chromatin

Chromatin is a complex of DNA and proteins, mainly histones, found in the nucleus of eukaryotic cells. Its primary function is to package long DNA molecules into a more condensed, denser shape, which prevents the strands from becoming tangled and plays a significant role in reinforcing the DNA during cell division. Due to its structure, chromatin also plays a crucial role in the regulation of gene expression. Certain regions of chromatin can be made accessible or inaccessible to the proteins that transcribe genetic information stored in the DNA, thereby controlling the expression of specific genes.
02

(b) Nucleolus

The nucleolus is a dense, membrane-less structure found within the cell nucleus. Its main function is the synthesis of ribosomal RNA (rRNA), a key component of ribosomes. The rRNA molecules are combined with proteins to form ribosomal subunits, which are then transferred to the cytoplasm where they assemble into ribosomes. Although the nucleolus does not directly store, express, or transmit genetic information, it plays a crucial role in protein synthesis by providing the necessary machinery (ribosomes) for the translation process.
03

(c) Ribosome

Ribosomes are complex molecular machines found in the cytoplasm of cells and are responsible for the synthesis of proteins. They use the genetic information contained in the messenger RNA (mRNA), which is transcribed from DNA, as a template to assemble amino acids into proteins. This process is called translation. Hence, ribosomes play a critical role in the expression of genetic information since they enable cells to produce specific proteins based on the instructions received from mRNA.
04

(d) Mitochondrion

Mitochondria are double-membraned organelles found in the cytoplasm of eukaryotic cells. They play a central role in cellular respiration and energy production but are also unique in that they contain their own genetic material in the form of a small circular DNA molecule. This DNA encodes for some proteins necessary for the proper functioning of the mitochondria. As a result, mitochondria can replicate independently of the cell and have their own machinery for the expression and transmission of genetic information, separate from the nuclear genome.
05

(e) Centriole

Centrioles are cylindrical structures composed of microtubules, found in pairs within the centrosome of animal cells. Their primary role is in cell division, where they help in the formation of the mitotic spindle, a structure that ensures the correct segregation of chromosomes. Although centrioles do not directly store, express, or transmit genetic information, they play a vital role in the accurate distribution of genetic material during cell division, ensuring that the daughter cells receive the correct set of chromosomes.
06

(f) Centromere

The centromere is a specialized region on a chromosome where the two sister chromatids are held together, and it also serves as the attachment site for spindle fibers during cell division. The centromere is crucial for proper chromosome segregation during cell division, ensuring that each daughter cell receives an identical set of genetic information. While the centromere does not directly express or transmit genetic information, it is essential for accurate transmission of genetic material between cell generations.

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Most popular questions from this chapter

Describe the "folded-fiber" model of the mitotic chromosome.

In this chapter, we focused on how chromosomes are distributed during cell division, both in dividing somatic cells (mitosis) and in gamete- and spore- forming cells (meiosis). We found many opportunities to consider the methods and reasoning by which much of this information was acquired. From the explanations given in the chapter, answer the following questions. (a) How do we know that chromosomes exist in homologous pairs? (b) How do we know that DNA replication occurs during interphase, not early in mitosis? (c) How do we know that mitotic chromosomes are derived from chromatin?

During oogenesis in an animal species with a haploid number of \(6,\) one dyad undergoes nondisjunction during meiosis II. Following the second meiotic division, this dyad ends up intact in the ovum. How many chromosomes are present in (a) the mature ovum and (b) the second polar body? (c) Following fertilization by a normal sperm, what chromosome condition is created?

Describe the role of meiosis in the life cycle of a vascular plant.

Contrast spermatogenesis and oogenesis. What is the significance of the formation of polar bodies?
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