Micro Chapter 8 Key Terms

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Tortora, Funke, Case Ch 8 Microbial Genetics

alarmone

A chemical signal that promotes a cell's reponse to environmental stress

Ames test

A procedure using bacteria to identify potential carcinogens

anticodon

The three nucleotides by which a tRNA recognizes an mRNA codon

auxotroph

A mutant microorganism with a nutrional requirement that is absent in the parent

bacteriocin

An antimicrobial peptide produced by bacteria that kills other bacteria

bacteriophage (phage)

A virus that iinfects bacterial cells

base pairs

The arrangement of nitrogenous bases in nucleic acids based on hydrogen bonding; in DNA, base pairs are A-T and G-C; in RNA, base pairs are A-U and G-C

base substitution

The replacement of a single base in DNA by another base, causing a mutation; also called point mutation

carcinogen

Any cancer-causing substance

catabolite repression

Inhibition of metabolism of alternate carbon sources by glucose

chromosome

The structure that carries hereditary information, chromosomes contain genes

codon

A sequence of three nucleotides in mRNA that specifies the insertion of an amino acid into a polypeptide

Competence

The physiological state in which a recipient cell can take an incorporate a large piece of donor DNA

conjugation

The transfer of genetic material from one cell to another involving cell-to-cell contact

conjugative plasmid

A prokaryotic plasmid that carries genes for sex pili and for transfer of the plasmid to another cell

corepressor

A molecule that binds to a repressor protein, enabling the repessor to bind to an operator

crossing over

The process by which a portion of one chromosome is exchanged with a portion of another chromosome

cyclic AMP (cAMP)

A molecule derived from ATP, in which the phosphate group has a cyclic structure; acts as a cellular messenger

degeneracy

Redundancy of the genetic code; that is, most amino acids are encoded by several codons

dissimilation plasmid

A plasmid containing genes encoding production of enzymes that trigger the catabolism of certain unusual sugars and hydrocarbons

DNA gyrase

See topisomerase

DNA ligase

An enzyme that covalently bonds a carbon atom of one nucleotide with the phosphate of another nucleotide

DNA polymerase

Enzyme that synthesizes DNA by copying a DNA template

donor cell

A cell that gives DNA to a recipient cell during genetic recombination

exon

A region of a eukaryotic chromosome that encodes a protein

F factor (fertility factor)

A plasmid found in the donor cell in bacterial conjugation

frameshift mutation

A mutation caused by the addition of deletion of one or more bases in DNA

free radical

A compound with an unpaired electron. See superoxide

gene

A segment of DNA (a sequence of nucleotides in DNA) encoding a functional product

generalized transduction

The transfer of bacterial chromosome fragments from one cell to another by a bacteriophage

genetic code

The mRNA codons and the amino acids they encode

genetic recombination

The process of joing pieces of DNA from different sources

genetics

The science of heredity and gene function

genome

One complete copy of the genetic information in a cell

genomics

The study of genes and their function

genotype

The genetic makeup of an organism

Hfr cell

A bacterial cell in which the F factor has become integrated into the chromosome; Hfr stands for high frequency of recombination

horizontal gene transfer

Transfer of genes between two organsims in the same generation. See also vertical gene transfer

inducer

A chemical of environmental stimulus that causes transcription of specific genes

induction

The process that turns on the transcription of a gene

insertion sequence (IS)

The simplest kind of transposon

intron

A region in a eukaryotic gene that does not code for a protein or mRNA

lagging strand

During DNA replication, the daughter strand that is synthesized discontinuously

leading strand

During DNA replication, the daughter strand that is synthesized continuously

light-repair enzyme

See photolyase.

Messenger RNA (mRNA)

The type of RNA molecule that directs the incorporation of amino acids into proteins

methylase

An enzyme that attaches methyl groups (-CH3) to a molecule; methylated cytosine is protected from digestion by restriction enzymes

microRNA (miRNA)

Small, single-stranded RNA that prevent translation of a complementary mRNA

missense mutation

A mutation that results in the substitution of an amino acid in a protein

mutagen

An agent in the environment that brings about mutations

mutation

Any change in the nitrogenous base sequence of DNA

mutation rate

The probability that a gene will mutate each time a cell divides

negative (indirect) selection

The process of identifying mutations by selecting cells that do not grow using replica plating

nonsense codon

A codon that does not encode any amino acid

nonsense mutation

A base substitution in DNA that results in a nonsense codon

nucleotide excision repair

The repair of DNA involving removal of defective nucleotides and replacement with functional ones

operator

The region of DNA adjacent to structural genes that controls their transcription

operon

The operator and promoter sites and structural genes they control

phage

See bacteriophage

Phenotype

The external manifestations of an organism's genotype, or genetic makeup

photolyase

An enzyme that splits thymine dimers in the presence of visible light

point mutation

See base substitution

positive (direct) selection

A procedure for picking out mutant cells by growing them

promoter

The starting site on a DNA strand for transcription of RNA by RNA polymerase

R

Used to represent nonfunctional groups of a molecule See also resistance factor

r-determinant

A group of genes for antibiotic resistance carried on R factors

recipient cell

A cell that receives DNA from a donor cell during genetic recombination

replica plating

A method of inoculating a number of solid minimal culture media from an original plate to produce the same pattern of colonies on each plate

replication fork

The point where DNA strands separate and new strands will be synthesized

repression

The process by which a repressor protein can stop the synthesis of a protein

repressor

A protein that binds to the operator site to prevent transcription

resistance (R) factor

A bacterial plasmid carrying genes that determine resistance to antibiotics

resistance transfer factor (RTF)

A group of genes for replication and conjugation on the R factor

RNA primer

A short strand of RNA used to start synthesis of the lagging strand of DNA, and to start the polymerase chain reaction

semiconservative replication

The process of DNA replication in which each double-stranded DNA molecule contains one original strand and one new strand

sense codon

A codon that codes for an amino acid

short tandem repeats (STRs)

Repeating sequences of 2- to 5- nucleotides

snRNP

Small nuclear ribonucleoprotein (pronounced "snurp") - Short RNA transcript plus protein that combines with pre-mRNA to remove introns and join exons together

specialized transduction

The process of transferring a piece of cell DNA adjacent to a prophage to another cell

spontaneous mutation

A mutation that occurs without a mutagen

structural gene

A gene that determines the amino acid sequence of a protein

terminator

The site on a DNA strand at which transcription ends

topoisomerase

Enzyme that relaxes supercoiling of DNA ahead of replication form; separates DNA circles at the end of DNA replication

transcription

The process of synthesizing RNA from a DNA template

transduction

The transfer of DNA from one cell to another by a bacteriophage. See also generalized trasduction; specialed transduction

transfer RNA (tRNA)

The type of RNA molecule that brings amino acids to the ribosomal site where they are incorporated into proteins

transformation

(1) The process in which genes are transferred from one bacterium to another as "naked" DNA in solution. (2) The changing of a normal cell into a cancerous cell

translation

The use of mRNA as a template in the synthesis of protein

transposon

A small piece of DNA that can move from one DNA molecule to another

vertical gene transfer

Transfer of genes from an organism or cell to its offspring

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