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29 Cards in this Set
- Front
- Back
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DNA
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Deoxyribonucleic Acid
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3 components of DNA
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1. A nitrogenous base
2. A pentose sugar - deoxyribose 3. A phosphate group |
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4 nigtrogenous bases
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A - Adenine
T - Thymine G - Guanine C - Cytosine |
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Chargaff's Rules
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In the DNA within a single species the # of adenines approximately equals the # of thymines and the # of guanine approx equals the # of cytosines
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Percentages of nitrogenous bases in human DNA
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A & T 30.3% each
G 19.5% C19.9% |
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Replication Fork
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Y shaped region where parental DNA is being unwound
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Heilcase
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Unwinds parental double helix at replication fork
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Single Strand Binding Protein
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Binds to and stabilizes single-stranded DNA until it can be used as a template
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Topoisomerase
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Relieves "overwinding" strain ahead of replication forks by breaking,swiveling, and rejoining DNA strands
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Primase
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Synthesizes an RNA primer at 5' end of leading strand and of each Okazaki fragment of lagging strand
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DNA pol III
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Using parental DNA as template, synthesizes new DNA strand by covalently adding nucleotides to the 3' end of a pre-existing DNA strand or RNA primer
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DNA pol I
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Removes RNA nucleotides of primer from 5' end and replaces them with DNA nucleotides
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DNA ligase
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Joins 3' end of DNA that replaces primer to rest of leading strand and joins Okazaki fragments of lagging strand
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Chromosome
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Long DNA molecule and associated proteins condensed and folded -carrying genetic material
Found in nucleus |
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Chromatid
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A chromosome that has replicated and is attached to it's counterpart by a centrome - each identical part is a chromatid. When separated -they are each a chromosome
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Chromatin
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long thin strand of DNA plus structural proteins that will condense into a chromosome when the cell is dividing
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leading strand
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The new complementary DNA strand synthesized continuously along the template strand toward the replication fork in the 5'-3' direction
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lagging strand
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A discontinuously synthesized DNA strand that elongates by means of Okazaki fragments, each synthesized in a 5' -> 3' direction away from the replication fork
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mismatch repair
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enzymes remove and replace incorrectly paired nucleotides that have resulted from replication errors
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DNA nuclease
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A DNA cutting enzyme cuts out segments of DNA with mismatched/damaged nucleotides
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Nucleotide incision repair
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Polymerase III fills in missing nucleotides
DNA ligase seals the free end of the new DNA to the old DNA, making the strand complete.Telo |
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Telomeres
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The tandomly repetitive DNA at the end of a strand of eukaryotic chromosome's DNA molecule that protects the gene from being eroded during successive replications
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Telemerase
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Catalyzes the lengthening of telomeres in eukaryotic germ cells, restoring their original length and compensating for the shortening that occurs during replication
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Histones (2 nm fiber)
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Proteins responsible for the 1st level of DNA packing in chromatin.
More than 1/5 of histone's 100 amino acids are +charged (lysine or arginine and bind tightly to -charged DNA |
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Nucleosome (10 nm fiber)
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The basic bead-like unit of DNA packing consisting of a segment of DNA wound around a protein core made up of two copies of each of the 4 types of histones
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30 nm fiber
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Formed when interactions between the histone tails of one nucleosome and the linker DNA and nucleosomes on either side.
A fifth histone H1 is involved at this level |
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Looped domains ( 300nm fiber)
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The 30 nm fiber forms loops attached to a chromosome scaffold made of proteins.
1 type of topoisomerase and H1 are present also |
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Metaphase chromosome
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The looped domains coil and fold in a highly specific and precise manner, creating a chromosome with chromatids 70nm wide
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Heterochromatin
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the centromeres and telomeres of chromosomes existing in a highly condensed state during interphase
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