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Results of fission
Mother cell goes into two identical daughter cells
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What is F pilus?
Bridge between bacteria
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Clone =
Population of genetically identical cells
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Colony =
Visible mass of cells
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G0
Cells not actively replicating
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S
Synthesis and replication
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Cytokenisis
Generation of new cell
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Mitosis produces
2 identical diploid (2n) cells
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Meiosis
Produces 4 non identical haploid (n) cells
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Holliday structure
Where crossing over occurs.. then they will move down and more will cross at a different spot.
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Chiasma
Touching point where exchange was made � only in meiosis
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Sexual reproduction � carried out twice to get daughter cells with half of the info
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Mitosis produces
- In both prokaryotic and eukaryotic cells, the genetic material is organized into
- chromosomes.
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The Cellular Environment
- � Cytoplasm�the inside of a cell
- � Water
- � Hydrophilic and Hydrophobic Molecules
- � Carbohydrates
- � Lipids
- � Proteins, including enzymes
- � Membrane�made of lipids and proteins
- � Organelles
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Chromosomes
Double-stranded DNA with associated proteins and sometimes RNA
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Prokaryotic cells contain what kind of chromosomes?
one circular chromosome plus smaller plasmids
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Most eukaryotic cells contain what kind of chromosomes?
several large linear chromosomes
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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.
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Clone�
a population of genetically identical cells.
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Colony�
a visible mass of cells.
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Cells, the basic units of all living things, are enclosed by
membranes.
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Chromosomes, the cellular structures that carry the genes, are composed of
DNA, RNA, and protein.
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In eukaryotes, chromosomes are contained within a membrane-bounded nucleus;
in prokaryotes they are not.
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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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Mitosis
When eukaryotic cells divide, they distribute their genetic material equally and exactly to their offspring.
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Components of mitosis:
- � Microtubules and Centrioles
- � Spindle
- � Microtubule organizing centers (MTOCs)
- � Centrosomes and centrioles
- � Pericentriolar material
- � Aster
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As a cell enters mitosis, its duplicated chromosomes
condense into rod-shaped bodies (prophase).
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As mitosis progresses, the chromosomes migrate to the
equatorial plane of the cell (metaphase).
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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).
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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.
- Prophase I: Leptonema
- � Chromosomes condense
- � Each chromosome has two sister chromatids
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Prophase I: Zygonema
- � Synapsis of homologous chromosomes
- � Synaptonemal complex
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Prophase I: Pachynema
- � Chromosomes condense further
- � Bivalent
- � Tetrad
- � Crossing over occurs
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Prophase I: Diplonema
� Paired chromosomes separate slightly but are in contact as chiasmata
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Prophase I: Diakinesis
- � Nuclear envelope fragements
- � Spindle fibers 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
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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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Outcome of meiosis?
- � Daughter cells are NOT genetically identical
- � Maternal and paternal homologues synapse, then disjoin. Different pairs 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).
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During meiosis I,
homologous chromosomes pair (synapse), exchange material (cross over), and separate (disjoin) from each other.
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During meiosis II,
chromatids disjoin from each other.
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In many organisms, the haploid products of meiosis develop directly into
gametes.
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In plants, the products of meiosis divide mitotically to form haploid
gametophytes.
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The gametophytic phase of a plant�s life cycle alternates with the sporophytic phase, which is diploid; meiosis occurs in the sporophyte.
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Genetics in the Laboratory: An Introduction to Some Model Research Organisms
Geneticists focus their research on microorganisms, plants, and animals well suited to experimentation.
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Eschericia coli,a Bacterium
- � ?Rod-shaped bacterium
- � ?Molecular Genetics
- � ?4.6 ?106base pairs
- � ?4288 protein-coding genes
- � ?Single circular chromosome
- � ?Bacteriophages
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Saccharomyces cerevisiae,Baker�s Yeast
- � ?Unicellular fungus
- � ?16 linear chromosomes
- � ?12 ?106base pairs
- � ?6268 genes
- � ?Reproduces sexually and asexually
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Drosophila melanogaster,a Fruit Fly
- � ?Insect
- � ?Anatomically complex
- � ?170 ?106base pairs
- � ?13,792 genes
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Caenorhabditis elegans,a Round Worm
- � ?Model for animal development
- � ?Hermaphroditic
- � ?100 ?106base pairs
- � ?20,512 genes
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Mus musculus,the Mouse
- � ?Biomedical research
- � ?Comparative genomics
- � ?2.9 ?109base pairs
- � ?25,396 genes
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Danio rerio,the Zebrafish
- � ?Model for vertebrate development
- � ?Transparent eggs; external fertilization
- � ?1.6 ?109base pairs
- � ?23,524 genes
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Arabidopsis thaliana,a Fast-growing Plant
- � ?Self-fertilizing
- � ?Model for agriculturally significant plants
- � ?157?106base pairs
- � ?27,706 genes
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Homo sapiens,Our Own Species
- � ?Cell culture
- � ?DNA Cloning
- � ?The Human Genome Project
- � ?3.2 ?109base pairs
- � ?20,000 to 25,000 genes
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The bacterium E. coliis the premier prokaryote for
genetic analysis.
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Model eukaryotes include
yeast (S. cerevisiae), a fruit fly (D. melanogaster), a round worm (C. elegans), the mouse (M. musculus), the zebrafish (D. rerio), and a fast-growing plant (A. thaliana).
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Techniques such as ____ and _____have made it possible to study the genetic material of human beings and many other organisms.
cell culture and DNA cloning
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