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81 terms

Chpt 7-Microbial Genetics

Chpt7-Microbial Genetics-PTC- Professor Nelson
STUDY
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allele
one of two alternate forms of a gene that can have the same locus on homologous chromosomes and are responsible for alternative traits
anticodon
group of three bases on a tRNA molecule that are complementary to an mRNA codon
antiparallel
strands run in opposite direction in the arrangement of the sugar-phosphate backbones in a DNA double helix.
carcinogen
any substance that causes cancer
chromosome
in a eukaryotic cell, one of the structures in the nucleus that are made up of DNA and protein; in a prokaryotic cell, the main ring of DNA.
codon
a specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid
dark repair
Mechanism for repair of damaged DNA by several enzymes that do not require light for activation; they excise defective nucleotide sequences and replace them with DNA complementary to the unaltered DNA strand
deaminating agent
point mutation; chemical mutagen/agent that removes an amino group from base of normal DNA
dimer
Two adjacent pyrimidines bonded together in a DNA strand, usually as a result of exposure to ultraviolet rays
DNA polymerase
enzyme that moves along behind the replication fork to makes a long strand of DNA; attaches at the replication fork; "proofreads" new DNA strands
DNA replication
process of making a new strand of DNA by using an old strand as a template
exon
sequence of DNA that codes information for protein synthesis in eukaryotic cells
feedback inhibitor
the inhibition of a enzyme in a metabolic pathway by the final product of that pathway
frameshift mutation
a mutation in which a single base is added to or deleted from DNA
gene
functional unit within a chromosome or plasmid sequence of DNA
genetic code
codon to specific amino acid
genotype
the genetic makeup of an organism; mutations always change the genotype
heredity
the passing (transmission) of traits from parents to offspring
induced mutation
produced by mutagens (chemical agents or radiation); increases mutation rate above spontaneous mutation rate
insertion
A mutation involving the addition of one or more nucleotide pairs to a gene.
intron
A noncoding, intervening sequence within a eukaryotic gene.
lagging strand
backward; new strand of DNA formed in short, discontinuous DNA setments during DNA replication
leading strand
new strand of DNA formed as a continuous strand during DNA replication; easier direction for polymerase to add neucleotides
alkylating agent
a chemical mutagen that can add alkyl groups to DNA bases, altering their shapes and causing errors in the base paring
Ames test
test used to determine whether a particular substance is mutagenic, based on its ability to induce jmutatjions in auxotrophic bacteria`
attenuation
the weakening of the disease-producing ability of an organism
auxotroph
an organism that used carbon dioxide gas to synthesize organic molecules
base analog
a chemical mutagen similar in molecular structure to one of the nitrogenous bases found in DNA that causes point mutation
constitutive enzyme
an enzyme that is synthesized continuously regardless of the nutrients available to the organism
end-product inhibition
feedback inhibition
enzyme repression
mechanism by which the presence of a particular metabolite reppresses the genes coding for enzymes used in its synthesis
fluctuation test
a test used to determine that resistance to chemical substances occurs spontaineously rather than being induced
inducer
a substance that binds to and inactivates a repressor protein
inducible enzyme
an enzyme coded for by a gene that is sometimes active and sometimes inactive
ligase
an enzyme that joins together DNA segments
light repair
aka photoreactivation; repair of DNA dimers by a light-activated enzyme
messeger RNA (mRNA)
a type of RNA that carries the information from DNA to dictate the arrangement of amino acids in a protein
mutagen
an agent that increases the rate of mutations
mutation
permanant alteration in an organism's DNA
nonsense codon
aka terminator codon; a set of three bases in a gene (or mRNA) that does not code for an amino acid
Okazaki fragment
one of the short, discontinuous DNA segments formed on the lagging strand during DNA replication
uracil
swapped for thymine and pairs with adenine in RNA
phenotype
specific characteristics displayed by organism
photoreactivation
aka light repair
point mutation
mutation that affect a single base
polymerase chain reaction
technique that produces a billion or more identical copies of a DNA fragment without needing a celel
polyribosome
long chain of ribosomes attached at different points along an mRNA molecule
prototroph
a normal, nonmutant organism
radiation
light rays, such as X-rays and UV rays, that can act as mutagens
replication fork
points at which two strands of DNA separate to allow replication of DNA
restriction endonuclease
an enzyme that cuts DNA at precise base sequences
reverse transcription
an enzyme found in retroviruss that copies RNA to DNA
ribosomal RNA (rRNA)
site for protein synthesis; combines with specific proteins to form ribosomes;
RNA polymerase
an enzyme that binds to one strand of exposed DNA during transcription and catalyzes the synthesis to RNA from the DNA template
semiconservative replication
process in replication that ends up with a strand of old (parent) DNA and new DNA
sense codon
a set of three DNA bases that code for an amino acid
spontaneous mutation
arise during DNA replication; occur in the absence of any agent
start codon
the first codon in a molecule of mRNA which begins the sequence of amino acids in protein synthesis
stop codon
aka terminator codon; the last codon to be translated in a molecule of mRNA, causing the ribosome to release from the mRNA
structural gene
a gene that carries information for the synthesis of a specific polypeptide
transcription
DNA to RNA; newly formed RNA released from DNA
transfer RNA (tRNA)
function is to transfer amino acids from the cytoplasm to the ribosomes for placement in a protein molecule; link between the codons and corresponding amino acids; each has an anticodon
translation
RNA to protein;
genetics
The study of of heredity
eukaryotic cell
a cell that has a distinct cell nucleus and other membrane-bound structures
prokaryotic cell
a cell that lacks a cell nucleus; bacteria; contains a single circular chromosome
thymine, cytosine, adenine, guanine
the four neuclotides that make up DNA
DNA
where all information is stored; the product of replication
hydrogen bonds
holds together the nucleotide base pairs
steps to transfer DNA to protein
replication (get DNA), transcription (get RNA), translation (get protein)
messenger RNA (mRNA)
carries information from DNA for synthesis of protein; has codons; attaches to ribosomes
frameshift mutation
mutation which can affect more than one base in DNA
chemical mutagens
base analogs, alkylating agents, deaminating agents, acridine derivatives
mustard gas
an alkylating agent
base analog
substitutes "look-alike" molecule for notmal nitrogenous base during DNA replication
deaminating agent
removes an amino acid group from a nitrogenous group; results to a point mutation; ex; nitrous acid that is added to hot dogs
alkylating agent
adds alkyl group which results in incorrect pairing; results to a point mutation; ex: mustard gas
acridine derivative
inserts DNA ladder between backbones to form a new rung; distorts helis; causes framshift mutation;
light repair (photoreactivation)
uses an enzyme that is activated by visivle light and breaks bonds between pyrimidines of a dimer
free radical
highly reactive molecule, atom or ion that in turn attackS other cell molecules, including DNA
dark repair
uses several enzymes that do not require light for activation; excise defective DNA replace it with DNA complementar to the normal strand