10.1 Cell Division
2 min read•june 14, 2024
DNA, the blueprint of life, comes in different packages. Prokaryotes keep it simple with a single circular , while eukaryotes go big with multiple linear ones. This packaging affects how cells divide and pass on genetic info.
Chromosomes are like DNA storage units, housing genes that determine traits. During cell division, these units undergo a fascinating compaction process. From loose to tightly coiled chromosomes, this dance ensures accurate genetic transmission to new cells.
Genome Structure and Compaction
Prokaryotic vs eukaryotic genomes
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- Prokaryotic genomes typically consist of a single circular chromosome located in the region, lack membrane-bound organelles including a , and have a generally smaller genome size compared to eukaryotes (bacteria)
- Eukaryotic genomes contain multiple linear chromosomes enclosed within a membrane-bound nucleus, possess membrane-bound organelles, have a generally larger genome size compared to prokaryotes, and contain non-coding DNA sequences such as introns and regulatory elements (humans)
- Some prokaryotes reproduce through , a simpler form of cell division
Chromosomes, genes, and traits
- Chromosomes are compact structures composed of DNA and proteins that contain genetic material passed from parent cells to daughter cells during cell division, with the number varying between species (humans have 46 chromosomes in somatic cells)
- Genes are segments of DNA that code for specific proteins or functional RNA molecules, determine the traits and characteristics of an organism, and are passed from parent cells to daughter cells during cell division
- Traits are observable characteristics of an organism determined by the expression of one or more genes and inherited from parent cells to daughter cells through the transmission of genes during cell division (eye color)
Chromosome compaction in cell division
- : Chromatin (DNA and associated proteins) is loosely packed and dispersed throughout the nucleus, with occurring during the S phase
- : Chromatin condenses and becomes tightly coiled, forming visible chromosomes consisting of two sister joined at the , with playing a crucial role in chromosome compaction
- The begins to form, with moving to opposite poles of the cell
- : Chromosomes align at the equatorial plane of the cell, with centromeres of the chromosomes attaching to the spindle fibers
- : Sister chromatids separate and move towards opposite poles of the cell while remaining condensed
- : Chromosomes begin to decondense and uncoil, the nuclear envelope re-forms around the chromosomes in each daughter cell, and (division of the cytoplasm) occurs, resulting in two genetically identical daughter cells with the same number of chromosomes as the parent cell
Cell Division Types
- : A type of cell division that produces two genetically identical daughter cells, important for growth, repair, and asexual reproduction
- : A specialized form of cell division that produces four genetically diverse haploid cells, crucial for sexual reproduction
- The encompasses the entire process of cell growth and division, including interphase and the stages of mitosis
Key Terms to Review (34)
Anaphase: Anaphase is a stage in cell division where the sister chromatids of each chromosome are pulled apart and moved towards opposite poles of the cell. This critical phase ensures that each daughter cell will receive an identical set of chromosomes, contributing to genetic stability during cell division. Anaphase occurs following metaphase and is crucial in both mitosis and meiosis, facilitating accurate chromosome segregation.
Binary fission: Binary fission is a form of asexual reproduction in which a single organism divides into two identical daughter cells. This process is primarily observed in prokaryotic cells and is crucial for their growth and reproduction, enabling rapid population increases. It also plays a significant role in the study of cell division, contributing to our understanding of how organisms reproduce and evolve.
Cell cycle: The cell cycle is a series of events that take place in a cell leading to its division and replication. This process is crucial for growth, development, and tissue repair in living organisms, ensuring that genetic material is accurately passed on to daughter cells during cell division.
Centrioles: Centrioles are cylindrical organelles composed mainly of a protein called tubulin. They play a crucial role in cell division by helping to organize the mitotic spindle and ensuring proper chromosome separation.
Centrioles: Centrioles are cylindrical structures found in eukaryotic cells, typically occurring in pairs, and play a crucial role in cell division by organizing the microtubules that separate chromosomes. They are composed of a protein called tubulin and are essential for the formation of the mitotic spindle, which ensures accurate distribution of chromosomes to daughter cells during cell division. Centrioles are also involved in the formation of cilia and flagella, contributing to cell movement and signaling.
Centromere: The centromere is a region of a chromosome that links sister chromatids. It plays a crucial role in chromosome segregation during cell division.
Centromere: A centromere is a specialized region of a chromosome that serves as the attachment point for spindle fibers during cell division, ensuring proper segregation of chromosomes into daughter cells. It plays a critical role in both mitosis and meiosis, contributing to the accurate distribution of genetic material. The centromere is essential for maintaining chromosome stability and integrity throughout the cell cycle.
Chromatids: Chromatids are identical halves of a duplicated chromosome formed during cell division. Each chromatid contains one DNA molecule and is joined to its sister chromatid by a centromere.
Chromatin: Chromatin is a complex of DNA and protein found in the nucleus of eukaryotic cells that serves to package DNA into a more compact form, allowing for efficient regulation of gene expression and DNA replication. It plays a crucial role in determining the accessibility of DNA for transcription, replication, and repair processes, impacting how genes are expressed and regulated throughout the cell cycle.
Chromosome: A chromosome is a structure made of DNA and proteins that carries genetic information. Each chromosome consists of a single, long DNA molecule wrapped around histone proteins, forming a compact and organized unit that plays a critical role during cell division, inheritance, and reproduction.
Cytokinesis: Cytokinesis is the process that follows cell division, where the cytoplasm of a parent cell is divided into two daughter cells, completing the overall cell division. This process is crucial for ensuring that each daughter cell receives a full set of organelles and sufficient resources to function effectively after mitosis or meiosis.
DNA replication: DNA replication is the biological process of producing two identical copies of a DNA molecule from a single original DNA strand. This process is crucial for cell division, ensuring that each new cell receives an exact copy of the genetic material. It is fundamental for both prokaryotic and eukaryotic organisms, facilitating growth, development, and repair by accurately duplicating the genetic instructions required for life.
G2 of Interphase: G2 of Interphase is the final sub-phase of Interphase where the cell undergoes rapid growth and prepares for mitosis. It involves the synthesis of proteins and organelles needed for cell division.
Gene: A gene is a specific sequence of DNA that contains the instructions for building proteins, which are essential for the growth, development, and functioning of living organisms. Genes serve as the basic unit of heredity, passed from parents to offspring, influencing traits and characteristics. Understanding genes is crucial as they play a vital role during processes like cell division, where they are replicated and distributed to daughter cells to ensure proper functioning and continuity of life.
Histone: Histones are highly alkaline proteins that play a crucial role in the organization and packaging of DNA within the nucleus of eukaryotic cells. By forming nucleosomes, histones help condense long strands of DNA into a more compact structure, facilitating efficient cell division, protecting DNA integrity, and regulating gene expression.
Histone acetylation: Histone acetylation is the addition of an acetyl group to histone proteins, leading to a more relaxed chromatin structure and increased gene expression. This process is crucial for regulating access to DNA by transcriptional machinery.
Histone proteins: Histone proteins are essential components of chromatin that help package DNA into structural units called nucleosomes. They play a critical role in gene regulation and DNA replication.
Homologous: Homologous chromosomes are pairs of chromosomes that have the same structure and carry genes for the same traits at the same loci. They pair up during meiosis in cell division.
Interphase: Interphase is the stage in the cell cycle where the cell prepares for division, encompassing the growth and DNA replication necessary for successful cell division. It is crucial for cellular function as it allows the cell to grow, replicate its DNA, and produce proteins needed for mitosis or meiosis.
Intron: An intron is a non-coding segment of a gene that is transcribed into RNA but is removed during the process of RNA splicing before translation into a protein. Introns play a significant role in gene expression regulation and the evolution of new genes by allowing for alternative splicing, which can lead to multiple protein isoforms from a single gene.
Meiosis: Meiosis is a specialized form of cell division that reduces the chromosome number by half, resulting in the production of four genetically diverse gametes, or sex cells. This process is crucial for sexual reproduction, as it ensures genetic diversity and maintains the species' chromosome number across generations.
Metaphase: Metaphase is a stage in cell division where chromosomes align at the cell's equatorial plane, preparing for separation into daughter cells. During this critical phase, spindle fibers attach to the centromeres of the chromosomes, ensuring that each new cell will receive an accurate copy of the genetic material. The proper alignment of chromosomes is vital for maintaining genetic stability and preventing disorders related to improper chromosome distribution.
Mitosis: Mitosis is the process of cell division that results in two genetically identical daughter cells, each containing the same number of chromosomes as the original cell. This process is essential for growth, development, and tissue repair in multicellular organisms, linking it to various biological concepts including cellular organization and reproduction.
Mitotic spindle: The mitotic spindle is a structure composed of microtubules that segregates chromosomes into daughter cells during mitosis. It ensures accurate chromosome alignment and separation to facilitate cell division.
Mitotic spindle: The mitotic spindle is a structure formed by microtubules that organizes and separates chromosomes during cell division. This essential apparatus ensures that each daughter cell receives an accurate and equal distribution of genetic material, facilitating the orderly process of mitosis and maintaining genetic integrity in eukaryotic cells.
Nucleoid: The nucleoid is a region within prokaryotic cells where the cell's circular DNA is located, playing a crucial role in cellular processes such as replication and gene expression. Unlike eukaryotic cells, which have a defined nucleus, prokaryotic cells have their genetic material concentrated in this non-membrane-bound area, allowing for efficient regulation of DNA functions in processes like cell division and adaptation.
Nucleosome: A nucleosome is the fundamental unit of chromatin, consisting of a segment of DNA wound around a core of eight histone proteins. It helps in packaging DNA into a more compact structure within the nucleus.
Nucleus: The nucleus is a membrane-bound organelle found in eukaryotic cells that contains the cell's genetic material, organized as DNA molecules along with proteins to form chromosomes. It serves as the control center for cell activities, regulating gene expression and mediating the replication of DNA during cell division.
Prophase: Prophase is the first stage of mitosis and meiosis, where chromatin condenses into visible chromosomes and the mitotic spindle begins to form. During this phase, the nuclear envelope starts to break down, allowing the chromosomes to become more accessible for segregation. Prophase is crucial for proper cell division as it sets the stage for chromosome alignment and separation in later phases.
Sister chromatid: Sister chromatids are identical copies of a single chromosome, created during DNA replication prior to cell division. They are crucial for ensuring that each new daughter cell receives an exact copy of the genetic material during cell division processes like mitosis and meiosis. Each sister chromatid is connected at a region called the centromere, which plays an essential role during the segregation of chromosomes.
Spindle fiber: Spindle fibers are protein structures that form during cell division, specifically during mitosis and meiosis. They play a crucial role in the separation of chromosomes by attaching to the centromeres of chromosomes and helping to pull them apart towards opposite poles of the cell. This ensures that each daughter cell receives an identical set of chromosomes, which is vital for genetic stability and proper cellular function.
Telophase: Telophase is the final stage of mitosis, where two daughter nuclei form in a cell. Chromosomes decondense and the nuclear envelope reappears around each set of chromosomes.
Telophase: Telophase is the final stage of cell division, specifically during mitosis and meiosis, where the separated chromosomes reach opposite poles of the cell and begin to de-condense, ultimately leading to the formation of two distinct nuclei. This phase marks the end of nuclear division and prepares the cell for cytokinesis, where the cytoplasm divides, completing the overall cell division process.
Trait: A trait is a specific characteristic or feature of an organism that can be observed or measured. Traits can be physical, such as eye color or height, or behavioral, like feeding habits or mating calls. These characteristics are influenced by genetic factors and can be passed from one generation to the next through the process of cell division, where genetic material is replicated and distributed to daughter cells.