Chapter 2 Cellular Reproduction © John Wiley & Sons, Inc.
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Transcript of Chapter 2 Cellular Reproduction © John Wiley & Sons, Inc.
Chapter 2Cellular Reproduction
© John Wiley & Sons, Inc.
Chapter Outline
Cells and ChromosomesMitosisMeiosisLife Cycles of Some Model Genetic
Organisms
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Cells and Chromosomes
In both prokaryotic and eukaryotic cells, the genetic
material is organized into chromosomes.
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Eukaryotic: 23, non-circular, linear
Prokaryotic: 1, circular
Viruses: 1, DNA circular; 1, RNA linear
The Cellular EnvironmentCytoplasm / cytosol / Nucleus/ …the inside of a
cell….. Plasma membrane….the outside of the cell…
Water ( 70-80 %)
Hydrophilic and Hydrophobic Molecules; Amphiphatic
Carbohydrates (Glucose and Glycogen)
Lipids (Cholesterol, phospholipids and fatty acids)© John Wiley & Sons, Inc.
The Cellular Environment
Proteins (amino acids to polypeptide), including enzymes
Ribonucleoproteins, including RNAse as an enzyme
Membrane—made of lipids and proteins
Cell Wall: cellulose [murein-(sugars and amino acid)-in bacteria)
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Animal and Plant Cells
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Organelles:
Animal and Plant Cells
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Ribosome:is cell organelles that consist of RNA and proteins. They are responsible for assembling the proteins of the cell.
Mitochondria: is the cell's power producers. They convert energy into forms that are usableBy the cell.
Golgi:is responsible for manufacturing, warehousing, and shipping certain cellular products.
Lysosome:is a membranous sacs of enzymes. These enzymes are typically hydrolytic and can digest cellular macromolecules.
Endoplasmic Reticulum: is a network of tubules and flattened sacs that serve a variety of functions in the cell. The rough endoplasmic reticulum manufactures membranes and secretory proteins. The smooth ER has a wide range of functions including carbohydrate and lipid synthesis.
Plasma membrane: is a thin semi-permeable membrane that surrounds the cytoplasm of a cell, enclosing its contents. Its function is to protect the integrity of the interior of the cell by allowing certain substances into the cell, while keeping other substances out.
Cilia and flagella:are protrusions from some cells that aid in cellular locomotion. They are formed from specialized groupings of microtubules called basal bodies.
Nucleus:is a membrane bound structure that contains the cell's hereditary information and controls the cell's growth and reproduction.
Nucleolus contains nucleolar organizers which are parts of chromosomes with the genes for ribosome synthesis on them
Nuclear envelope:is a double membrane that contains the nucleus. These membranes separates the contents of the nucleus from the cytoplasm.
Nuclear pore: is a protein complex that helps to maintain the shape of the nucleus and assists in regulating the flow of molecules into and out of the nucleus.
Microtubules:are hollow rods, functioning primarily to help support and shape the cell as well as regulate cell cycle and division.
Microfilaments:or actin filaments are solid rods and are active in muscle contraction. They are particularly prevalent in muscle cells.
Cell wall:Outer covering of most cells that protects the bacterial cell and gives it shape.
Pilus:is a protein tube structure. It transfers genes from one bacteria to other bacteria.
Chloroplast:is the organelle where photosynthesis occurs in photosynthetic eukaryotes.
The organelle is surrounded by a double membrane.
Vacuole:structure in a plant cell that provides support and participates in a variety of cellular functions including storage, detoxification, protection, and growth.
Centriole: is found in animal cells and help to organize the assembly of microtubules during cell division.
Animal and Plant Cells
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No Organelles:
Chromosomes Double-stranded DNA with
associated proteins and sometimes RNA
Prokaryotic cells contain one circular chromosome plus smaller plasmids ( ?)
Most eukaryotic cells contain several large linear chromosomes plus a circular mitochondrial DNA
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Vocabulary for ChromosomesDiploid: cells with 2 copies of each chromosomesHaploid: cells with one copy of each chromosomesSomatic cells: any cells of an organism, diploid and go
under mitosis.Germ line: reproductive cells that give rise to gametesGametes: specialized cells (sperm and ova)Centromere: point of interaction of each chromosomes;
region of chromosomes required for its movement.
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Cell Division in Prokaryotes:Fission
A mother cell divides to produce two daughter cells.
The mother cell’s chromosome is duplicated prior to fission.
Each daughter cell receives one copy of the chromosome and more or less the rest of the content.
Clone—a population of genetically identical cells.
Colony—a visible mass of cells (1 to 250 cells).
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http://mitosissection2.tumblr.com/
Division time?Phases1- lag 2- log3- stationary4- death
Cell Division in Eukaryotes:Inter (I) Phase and Mitosis (M) Phase
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30 min to
Cells, the basic units of all living things, are enclosed by membranes.
Chromosomes, the cellular structures that carry the genes, are composed of DNA and protein.
In eukaryotes, chromosomes are contained within a membrane-bounded nucleus; in prokaryotes they are not.
Eukaryotic cells possess complex systems of internal membranes as well as membranous organelles such as mitochondria, chloroplasts, and the endoplasmic reticulum.
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Haploid eukaryotic cells possess one copy of each chromosome; diploid cells possess two copies.
Prokaryotic cells divide by fission (binary)
Eukaryotic cells divide by mitosis and meiosis.
Eukaryotic chromosomes duplicate when a cell’s DNA is synthesized; this event is characteristic of the S phase of the cell cycle.
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MitosisWhen eukaryotic cells divide, they distribute their genetic material
equally and exactly to their offspring.
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Inter-phase: Chromatin---Heterochromatin
---Eurochromatin
M-phase: Chromosomes
Mitosis in Animal Cells
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mechanical force?
Centrosomes, Microtubules, and Centrioles.
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Microtubule organizing centers (MTOCs)
Centrosome duplicates (S phase)
Centrosomes move to opposite sides of nucleusduring prophase.
Mitotic spindle assembles (microtubules=MT)
Spindle MTs make contact with chromosomes---centromere
(sequence repeated DNA sequence=heterochromatin=CEN sequences)
---kinetochore(protein-like containing structure)
Cytokinesis inAnimal and Plant Cells
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Cleavage furrow associated with the contractile ring (Actin and Myosin)
As a cell enters mitosis, its duplicated chromosomes condense into rod-shaped bodies (prophase).
As mitosis progresses, the chromosomes migrate to the equatorial plane of the cell (metaphase).
Later in mitosis, the centromere that holds the sister chromatids of a duplicated chromosome together splits, and the sisters chromatids separate (or disjoin) from each other (anaphase)
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As mitosis comes to an end, the chromosomes decondense and a nuclear membrane reforms around them (telophase).
Each daughter cell produced by mitosis and cytokinesis has the same set of chromosomes; thus, daughter cells are genetically identical.
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Meiosis
Sexual reproduction involves a mechanism that reduces the number of chromosomes by
half.
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Homologues
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Xx or Xy
Comparison ofMitosis and Meiosis
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Reduction
Non-reduction
Prophase I: Leptonema
Chromosomes condense
Each chromosome has two sister chromatids
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Prophase I: Zygonema
Synapsis (pairing) of homologous chromosomes
Synaptonemal complex
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The Synaptonemal Complex
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Function ?Structural...
Prophase I: Pachynema
Chromosomes condense further
Bivalent of chromosomesTetrad of chromatids
Crossing over occurs (exchange material)
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Prophase I: Diplonema
Paired chromosomes separate slightly but are in contact as chiasmata
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Chiasmata
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Prophase I: DiakinesisNuclear envelope fragments
Spindle fibers (MT) attach to kinetochores
Chromosomes move to central plane in pairs
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Metaphase I
Paired chromosomes are oriented toward opposite poles
Terminalization: chiasmata move toward telomeres
Why? Spo11-double-strand DNA breaker
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Anaphase I
Chromosome disjunction (separation of paired chromosomes)
Separated homologues move toward opposite poles
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Telophase I
Chromosomes reach the poles; nuclei forms
Spindle apparatus is disassembled
Daughter cells separated by membranes
Chromosomes decondense
Each chromosome still has two sister chromatids
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Prophase II
Chromosomes condense
Chromosomes attach to a new spindle apparatus
Sister chromatids are attached to spindle fibers from opposite poles
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Metaphase II
Chromosomes align at equatorial plane
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Anaphase II
Centromeres split
Chromatid disjunction—sister chromatids move toward opposite poles
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Telophase II
Separated chromatids gather at poles; daughter nuclei form
Each chromatid is now called a chromosome
Each daughter nucleus contains a haploid set of chromosomes
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Cytokinesis
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Daughter cells are NOT genetically identical
Maternal and paternal homologues synapse, then disjoin independently.
Homologous chromosomes exchange material by crossing over
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Diploid eukaryotic cells form haploid cells by meiosis, a process involving one round of chromosome duplication followed by two cell divisions (meiosis I and meiosis II).
During meiosis I, homologous chromosomes pair (synapse), exchange material (cross over), and separate (disjoin) from each other.
During meiosis II, chromatids disjoin from each other.
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Human 23 3,200 20 to 25,000
Life Cycle ofSaccharomyces cerevisiae
(yeast).
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Spermatogenesis and Oogenesis in Mammals
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Arabidopsis thaliana, plant
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In yeast, haploid cells with opposite mating types fuse
to form a diploid zygote, which then undergoes meiosis
to produce four haploid cells
Meiosis in the reproductive organs of Arabidopsis
produces microspores and megaspores, which
subsequently develop into male and female
gametophytes
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The double fertilization that occurs during
Arabidopsis reproduction creates a diploid
zygote, which develops into an embryo, and a
triploid endosperm, which develops into
nutritive tissue in the seed
In mice and other mammals, one cell from
female meiosis becomes the egg, whereas all
four cells from male meiosis become sperm
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