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Frederick Griffith studied two strains of pneumonia
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pathogenic and nonpathogenic
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heat-killed pathogenic + nonpathogenic bacteria
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= pathogenic bacteria (live disease-causing)
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transformation
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change in genotype and phenotype due to assimilation of external DNA by a cell
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Oswald Avery also proved that DNA was the molecule that transformed bacteria
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DNA or RNA in a protein coat
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infect by taking over a cell's metabolic machinery
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Bacteriophages
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viruses that infect bacteria
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Henry and Chase showed that DNA was the genetic material that infected the bacteria
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concentration of … [A] = [T] [C] = [G]
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x-ray crystallography
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image of DNA produced by x-rays diffracting when passing through DNA fibers
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DNA is a double helix, with two anti-parallel sugar-phosphate backbones, and nitrogenous bases in the molecule's interior
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DNA is a polymer of nucleotides connected by covalent bonds
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4 nitrogenous bases:
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Purines (double ring) [A] [G]
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Pyrimidines (single ring) - [C] [T]
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DNA base pairing
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PURINE always pairs with PYRIMIDINE
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2 of the same would be too wide/narrow
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3 hydrogen bonds between C and G
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2 hydrogen bonds between A and T
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S phase of Interphase
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DNA made from existing DNA strand
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semiconservative model
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one parent strand serves as a template to a complementary strand
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half of parent strand is conserved in each daughter strand
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origins of replication
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where replication of DNA molecule begins
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bacterial chromosome
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circular, single origin
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eukaryotic chromosome
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linear, thousands of origins
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replication fork
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Y-shaped region formed by unwinding of parent strands
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DNA polymerase
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proofreads each nucleotide as it's covalently bonded
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mismatch repair
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other enzymes remove and repair incorrect nucleotides
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nucleotide excision repair
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mutated strand is cut out by enzyme nuclease, and the gap is filled with DNA polymerase and ligase
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Mutations occur when uncorrected mismatched nucleotides are replicated and passed onto a daughter cell. Usually harmful and permanent genetic changes that support natural selection.
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- reference drawings -
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eukaryotic cell
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one long DNA double helix with large amnt. of protein =
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chromatin
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the long DNA fits in the nucleus through packing
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Cheatography n. The art of mapping complex subjects into clear, instantly navigable reference guides.
