Chapter 8 Flashcards
(20 cards)
Vertical gene transfer
the transfer of genetic material is from parents to offspring. It may be through sexual or asexual reproduction
Base substitution
Incorrect nucleotide incorporated during DNA synthesis
Most common
Point mutation: change of a single base pair
Chemicals that modify nucleobases
Chemical modifications change base pairing properties of nucleobases
Nucleotide substitution
Base analogs
Base pairing properties differ from those of nucleobases normally found in DNA
Nucleotide substitution
Intercalating agents
Insert between base pairs, pushing them apart
Addition or subtraction of nucleotides
Transposons
Randomly insert into DNA
Insertional inactivation
Radiation
Ultraviolet light (UV): cause thymine diners to form, error during repair process
X Rays: cause single- and double strand breaks in DNA, deletions
Mutations
Rare because alterations in DNA generally repaired before being passed to progeny
Single mutation is rare; two even more unlikely
Reversion: change back to original state (rare)
Spontaneous: Proofreading by DNA polymerase
DNA polymerase Removes the most repaired nucleotide and replaces it with the correct one
Error in nucleotide incorporation
Spontaneous: Mismatch repair
A protein binds to the site of the mismatch and cuts the on methylated strand. A short stretch of the strain is then degraded and DNA polymerase synthesizes a replacement.
Error in nucleotide incorporation
Spontaneous: Action of glycosylases
A glycosylase removes the oxidized nuclearbase. A short stretch of that strand is then degraded, and DNA polymerase synthesizes a new replacement
Modified nucleobase in DNA
Mutagen induced (Chemical): Proofreading and mismatch repair
Same as for spontaneous mutations
Error in nucleotide incorporation
Mutagen induced (UV light): Thymine dimer
Photoreactivation: The energy of light is used to break the covalent bond between the thigh me nucleo-bases, restoring the original molecule.
Excision repair: an enzyme removes a short stretch of the strand containing the diamine dimer; DNA polymerase then synthesize a replacement
SOS repair: especially DNA polymerase synthesizes DNA even when the template is extensively damaged; the cell me survive but no most mutations are introduced
DNA mediated transformation
Transformation involves uptake of naked DNA (DNA not within cell)
DNase prevents transformation
Griffith rat experiment
Living non-encapsulated cells were transformed by DNA from heat killed encapsulated cells by producing living encapsulated cells
Plasmid
Replicon that is independent of the chromosome and generally includes only nonessential genetic information
Transposon
Segment of DNA that directs its own movement to another location in chromosome or plasmid DNA
Genomic Island
Large genomic segment in a cell’s genome that originated in another species
Phage DNA
Phage genome that sometimes carries additional genes
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