Microbial Genetics (ch 9)
Transposons
DNA segment with an insertion sequence at each end, enabling it to migrate to another plasmid, to the bacterial chromosome, or to a bacteriophage
Operon
a genetic operational unit that regulates metabolism by controlling mRNA production; in sequence the unit consists of a regulatory gene, inducer or repressor control sites, and structural genes
Back-mutation
a mutation which contracts an earlier mutation, resulting in the restoration of the original DNA sequence
Mutations
a permanent inheritable alteration in the DNA sequence or content of a cell
Nitrogen base
a ringed compound of which pyrimidines and purines are types
Gene
a site on a chromosome that provides information for certain cell function; a specific segment of DNA that contains the necessary code to make a protein or RNA molecule
Exons
a stretch of eukaryotic DNA coding for a corresponding portion of mRNA that is translated into peptides; during transcription are separated from introns and spliced together into continuous mRNA transcript
tRNA
a transcript of DNA that specializes in converting RNA language into protein language
Induced
any alteration in DNA that occurs as a consequence of exposure to chemical or physical mutagens
Double helix
cellular DNA is in the form of double-stranded DNA twisted around each other
Point mutations
change that involves the loss, substitution, or addition of one of a few nucleotides
RNA genes
code for ribosomal and transfer RNA molecules
Structural Genes
code for the proteins of the cell
Regulatory genes
control the expression of structural and RNA genes
Chromosome
discrete cellular structure composed of neatly packaged DNA
RNA polymerase
enzyme that translates the code of DNA to RNA
Phenotype
expression of the genotype, which creates traits or certain structures and metabolic functions
Semiconservative
in DNA replication, the synthesis of paired daughter strands, each retaining a parent strand template
Replication
in DNA synthesis, the semiconservative mechanisms that ensure precise duplication of the parent DNA strands
Conjugation
in bacteria, the contact between donor and recipient cells associated with the transfer of genetic material such as plasmids; can involve special(sex) pili; also a form of sexual recombination in ciliated protozoans
Transformation
in microbial genetics, the transfer of genetic material contained in "naked" DNA fragments from a donor cell to a competent recipient cell
Transcription
mRNA synthesis; the process by which a strand of RNA is produced against a DNA template
Ames test
method of detecting mutagenic and potentially carcinogenic agents based upon the genetic alteration of nutritionally defective bacteria
Spontaneous
mutation in DNA caused by random mistakes in replication and not known to be influenced by any mutagenic agent; these mutations give rise to an organism's natural, or background, rate of mutation
Missense mutation
mutation in which a change in the DNA sequence results in a different amino acid being incorporated into a protein, with varying results
Nonsense mutation
mutation that changes an amino acid-producing codon into a stop codon, leading to premature termination of a protein
Silent mutation
mutation that, because of the degeneracy of the genetic code, results in a nucleotide change in both DNA and mRNA but not the resultant amino acid and thus, not the protein
Translation
protein synthesis; the process of decoding the messengerRNA code into a polypeptide
mRNA
single-stranded transcript that is a copy of the DNA template that corresponds to a gene
Codons
specific sequence of three nucleotides in mRNA (or sense strand of DNA) that constitutes the genetic code for a particular amino acid
Antiparallel
strands run opposite direction; one 5'-3' other 3'-5'
Genotype
sum of all three types of genes and constitute an organism's distinctive genetic make-up
Nucleotides
the basic structural unit of DNA and RNA; each nucleotide consists of a phosphate, a sugar, and nitrogenous base such as adenine, guanine, cytosine, thymine or uracil
Introns
the segments on split genes of eukaryotes that do not code for polypeptide; they can have regulatory functions
Anticodons
the trinucleotide sequence of transfer RNA that is complementary to the trinucleotide sequence of messenger RNA (the codon)
Gene expression
transcribed into mRNA and then translated into protein
Transduction
transfer of genetic material from one bacterium to another by a bacteriophage vector
Hydrogen Bonding
two strands adhere to one another by hydrogen bonds that connect base-base