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Microbiology Chapter 8

Terms in this set (77)

Activator
A regulatory protein that can bind to a specific DNA sequence and increase transcription of genes.
Anticodon loop
Region of a tRNA molecule containing three unpaired nucleotides that bind to a mRNA codon via complementary base pairing during translation.
Base excision repair
A DNA repair mechanism that cleaves damaged bases off the sugar-phosphate backbone. After endonuclease cleaves the phosphodiester backbone at the damaged site, a new, correct DNA strand is synthesized complementary to the undamaged strand.
Base substitution
Also called point mutation. A change in a single nucleotide within a nucleic acid sequence.
Biotechnology
An applied field of biology in which DNA and genomes are analyzed and artificial molecules of DNA are constructed for various purposes, such as forensics, agriculture, food safety, and medical research.
CDNA
A synthetic copy of DNA made using messenger RNA as the template for reverse transcriptase.
Chaperone
A protein that helps other proteins fold into their correct tertiary structure.
Chromosome
Part or all of an organism's genome; it is packaged into a highly compacted form.
Codon
A set of three nucleotides within mRNA that encodes a particular amino acid.
Daughter strand
One of the two growing strands formed during DNA replication; it is complementary to the parental strand, which serves as its template.
Deletion
The loss of one or more nucleotides from a DNA sequence.
DNA ligase
An enzyme that cells use to form a covalent bond at a nick in the phosphodiester backbone; also used in molecular biology laboratories to join pieces of DNA.
DNA polymerase
The group of enzymes responsible for replicating DNA.
DNA polymerase III
The enzyme in bacteria responsible for synthesizing the daughter strands during DNA replication.
Elongation
The middle phase of DNA synthesis, in which DNA polymerase adds dNTPs to the growing daughter strands.
Frameshift mutation
A gene mutation involving the insertion or deletion of one or more nucleotides that causes a shift in the codon reading frame.
Gel electrophoresis
An analytical method for separating a mixture of nucleic acids or proteins on the basis of their size and charge, by subjecting them to an electric field as the molecules migrate through a sieving gel medium.
Gene
A distinct series of nucleotides within DNA that has a distinct function (regulatory) or whose product has a distinct function (protein). The functional unit of heredity.
Gene expression
Transcription and translation of one or more specific genes.
Genome
The complete genetic content of an organism; the sequence of all the nucleotides in a haploid set of chromosomes.
Genotype
All or part of the genetic constitution of an individual organism or cell.
Global regulator
Protein that controls the expression of multiple genes.
Gyrase
A topoisomerase that introduces negative supercoils in double-stranded DNA; enables DNA to untwist during DNA replication.
Homolog
One of a group of genes or proteins with shared ancestry and whose DNA sequences and amino acid sequences are similar.
Horizontal gene transfer
The passage of genes from one genome into another, nonprogeny genome.
Hybridize
For a nucleic acid strand, to form base pairs with a complementary strand from a different source.
Induction
Increased transcription of target genes due to an inducer binding a repressor, which prevents repressor-operator binding.
Initiation
The first phase of DNA synthesis, in which the DNA helix unwinds, RNA primers attach, and DNA polymerase and accessory proteins assemble on the promoter; also a term to describe the initial events in transcription and in translation.
Insertion
The addition of nucleotides to the middle of a DNA sequence.
Inversion
A reversal of the orientation of a DNA fragment within a chromosome. It may allow or repress the transcription of a particular gene.
Lagging strand
During DNA replication, the daughter strand of DNA that is synthesized as a series of short fragments that are then ligated.
Leading strand
During DNA replication, the daughter strand of DNA that is formed by continuous elongation in the 5′-to-3′ direction.
Messenger RNA (mRNA)
An RNA molecule that encodes a protein.
Methyl mismatch repair
A DNA repair system that fixes misincorporation of a nucleotide after DNA synthesis. The unmethylated daughter strand is corrected to complement the methylated parental strand.
Missense mutation
A point mutation that alters the sequence of a single codon, leading to a single amino acid substitution in a protein.
Mutation
A heritable change in a DNA sequence.
Mutator
A strain of a microorganism that has an abnormally high frequency of mutations.
Nonsense mutation
A mutation that changes an amino acid codon into a premature stop codon.
Okazaki fragment
A short fragment of DNA that is synthesized on the lagging strand during DNA synthesis.
Operon
A collection of genes that are in tandem on a chromosome and are transcribed into a single RNA.
Origin (oriC)
The region of a bacterial chromosome where DNA replication initiates.
Parental strand
One of the two strands of a DNA double helix used as a template for the synthesis of a daughter strand during DNA replication.
Peptide bond
The covalent bond that links two amino acid monomers.
Phenotype
The outward expression of a genotype.
Plasmid
An extrachromosomal genetic element that may be present in some cells.
Point mutation
Also called base substitution. A change in a single nucleotide within a nucleic acid sequence.
Polymerase chain reaction (PCR)
A method to amplify DNA in vitro by using many cycles of DNA denaturation, primer annealing, and DNA polymerization with a heat-stable polymerase.
Promoter
A noncoding DNA regulatory region immediately upstream of a structural gene; needed for transcription initiation.
Pyrimidine dimer
A form of DNA damage caused by exposure to ultraviolet light, which results in the covalent bonding of two adjacent pyrimidines on a DNA strand. If not repaired, the dimer will be read incorrectly during DNA replication, resulting in a mutation to the DNA.
Reading frame
A sequence of nucleotides in DNA or RNA whose nonoverlapping triplets are potentially translatable into a polypeptide.
Recombinant DNA
A DNA molecule, prepared in a laboratory, that contains sequences from two or more source organisms (often different species).
Recombination
The enzyme-mediated process by which two DNA molecules exchange sections of DNA by cutting and splicing their helix backbones.
Replication fork
During DNA synthesis, the region of the chromosome that is being unwound.
Repression
The down-regulation of gene transcription.
Response regulator
A cytoplasmic protein that is phosphorylated by a sensor kinase, and once phosphorylated, modulates gene transcription by binding to DNA regulatory sequences.
Restriction endonuclease
A bacterial enzyme that cleaves double-stranded DNA within a specific short sequence, usually a palindrome.
Restriction enzyme site
A DNA sequence recognized and cleaved by a restriction endonuclease.
Restriction fragment length polymorphism (RFLP)
A difference in DNA sequence between strains or individuals that is identified as a difference in the length of DNA fragments cut by restriction endonucleases.
Reverse transcriptase
An enzyme that produces a double-stranded DNA molecule from a single-stranded RNA template.
RNA polymerase
Enzyme responsible for synthesizing an RNA copy from a DNA template during transcription.
RNA primer
A short segment of RNA, complementary to a specific region of a chromosome, that is required for DNA polymerase to carry out DNA replication.
Secreted
Referring to molecules that are transported out of a cell for a specific purpose, such as to signal another cell.
Semiconservative
Describing the mode of DNA replication whereby each new double helix contains one old, parental strand and one newly synthesized daughter strand.
Sense strand
The strand of DNA containing the sequence of nucleotides that is equivalent to the mRNA sequence synthesized from the template strand of DNA.
Sensor kinase
A transmembrane protein that phosphorylates itself in response to an extracellular signal and then transfers the phosphoryl group to a response regulator protein.
Sigma factor
A protein needed to bind RNA polymerase to a DNA promoter for the initiation of transcription in bacteria.
Silent mutation
A mutation that does not change the amino acid sequence encoded by an open reading frame. The changed codon encodes the same amino acid as the original codon.
SOS response
A coordinated cellular response to extensive DNA damage; includes error-prone repair.
Structural gene
A sequence of nucleotides that encodes a functional RNA molecule.
Supercoil
An extra twist or turn found in DNA, either positive (increases DNA winding) or negative (decreases DNA winding).
Template strand
A DNA strand (or an RNA strand in some viruses) that is used as a template for the synthesis of mRNA.
Termination
The final phase of DNA synthesis, in which DNA replication stops because DNA polymerase lands on a termination site.
Termination (ter) site
Also called terminus. A sequence of DNA that halts DNA replication by DNA polymerase.
Terminus
Also called terminus. A sequence of DNA that halts DNA replication by DNA polymerase.
Transcription
The synthesis of RNA complementary to a DNA template.
Transformation
1. The internalization of free DNA from the environment into bacterial cells. 2. The viral conversion of a normal cell to a cancer cell.
Vector
1. An organism (e.g., insect) that can carry infectious agents from one animal to another. 2. In molecular biology, a molecule of DNA into which exogenous DNA can be inserted to be cloned.
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