DNA
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RNA
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Stands for:
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Deoxyribo Nucleic Acid
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Ribo Nucleic Acid
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Definition:
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A nucleic acid that contains the genetic instructions used in the
development and functioning of all modern living organisms (scientists
believe that RNA may have been the main genetic material in primitive life
forms).
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Function:
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Medium of long-term storage and transmission of genetic information
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Transfer the genetic code needed for the creation of proteins from
the nucleus to the ribosome.
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Unique Features:
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The helix geometry of DNA is of B-Form. DNA is
protected in the nucleus, as it is tightly packed. DNA can be damaged by
exposure to ultra-violet rays.
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The helix geometry of RNA is of A-Form. RNA strands are
continually made, broken down and reused.RNA is more resistant to damage
by Ultra-violet rays.
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Predominant Structure:
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Double- stranded molecule with a long chain of
nucleotides
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A single-stranded molecule in most of its biological
roles and has a shorter chain of nucleotides
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Bases & Sugars:
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Deoxyribose sugar; phosphate backbone; Four bases: adenine, guanine,
cytosine and thymine
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Ribose sugar; phosphate backbone. Four bases: adenine, guanine,
cytosine, and uracil
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Pairing of Bases:
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A-T(Adenine-Thymine), G-C(Guanine-Cytosine)
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A-U(Adenine-Uracil), G-C(Guanine-Cytosine)
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Stability:
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Deoxyribose sugar in DNA is less reactive because of C-H bonds. Stable
in alkaline conditions. DNA has smallergrooves, which makes it harder
for enzymes to "attack" DNA.
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Ribose sugar is more reactive because of C-OH (hydroxyl) bonds.Not
stable in alkaline conditions. RNA has larger grooves, which makes it easier
to be attacked by enzymes.
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Propagation:
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DNA is self-replicating.
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RNA is synthesized from DNA when needed.
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Eukaryotic Cell
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Prokaryotic Cell
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Nucleus:
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Present
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Absent
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Number of chromosomes:
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More than one
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One--but not true chromosome: Plasmids
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Cell Type:
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Usually multicellular
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Usually unicellular (some cyanobacteria may be multicellular)
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True Membrane bound Nucleus:
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Present
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Absent
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Example:
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Animals and Plants
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Bacteria and Archaea
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Genetic Recombination:
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Meiosis and fusion of gametes
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Partial, undirectional transfers DNA
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Lysosomes and peroxisomes:
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Present
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Absent
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Microtubules:
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Present
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Absent or rare
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Endoplasmic reticulum:
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Present
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Absent
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Mitochondria:
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Present
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Absent
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Cytoskeleton:
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Present
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May be absent
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DNA wrapping on proteins.:
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Eukaryotes wrap their DNA around proteins called histones.
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Multiple proteins act together to fold and condense prokaryotic DNA.
Folded DNA is then organized into a variety of conformations that are
supercoiled and wound around tetramers of the HU protein.
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Ribosomes:
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larger
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smaller
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Golgi apparatus:
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Present
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Absent
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Chloroplasts:
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Present (in plants)
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Absent; chlorophyll scattered in the cytoplasm
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Flagella:
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Microscopic in size; membrane bound; usually arranged as nine doublets
surrounding two singlets
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Submicroscopic in size, composed of only one fiber
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Permeability of Nuclear Membrane:
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Selective
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not present
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Plasma membrane with steroid:
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Yes
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Usually no
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Cell wall:
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Only in plant cells and fungi (chemically simpler)
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Usually chemically complexed
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Cell size:
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10-100um
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1-10um
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