Microbial Genetics Flashcards 8

Comprehensive vocabulary flashcards based on the lecture notes on microbial genetics, covering DNA structure, replication, gene expression, genetic transfer mechanisms, operons, and mutations.

Genetics

The study of what genes are, how they carry information, how information is expressed, and how genes are replicated.

Gene

A segment of DNA that encodes a functional product, usually a protein.

Chromosome

A structure containing DNA that physically carries hereditary information and contains the genes.

Genome

All the genetic information in a cell, including chromosomes and plasmids.

Genomics

The molecular study of genomes.

Genotype

The full genetic composition of an organism, which remains constant.

Phenotype

The observable expression of genes in an organism, which changes depending on environmental conditions.

Central Dogma

The flow of genetic information stating that DNA encodes messenger RNA, which in turn encodes protein.

The Griffith Experiment

A classic experiment showing that heat-killed virulent S strain S. pneumoniae passed hereditary material to live nonpathogenic R strain, transforming them into virulent S strain.

Purines

Two-ringed nitrogenous bases in nucleic acids, comprising adenine and guanine.

Pyrimidines

Single-ringed nitrogenous bases, comprising cytosine and thymine in DNA, and cytosine and uracil in RNA.

Antiparallel Strands

The structural arrangement of DNA where two complementary strands run in opposite directions, designated by 5' and 3' ends.

Origin of Replication (Ori)

A specific sequence of DNA where replication initiates.

Helicase

An enzyme that opens the DNA helix by breaking hydrogen bonds between nitrogenous bases.

Topoisomerase II (DNA Gyrase)

An enzyme that relaxes supercoiled chromosomes to make DNA accessible for replication initiation.

Topoisomerase IV

An enzyme that introduces single-stranded breaks into concatenated circular chromosomes to release them from each other, and then reseals the DNA.

DNA Polymerase III

The primary enzyme that synthesizes DNA by adding nucleotides in the 5' to 3' direction.

DNA Polymerase I

An enzyme with exonuclease activity that removes RNA primers and replaces them with newly synthesized DNA.

DNA Ligase

An enzyme that seals gaps between Okazaki fragments on the lagging strand to form a continuous DNA strand.

Leading Strand

The DNA strand synthesized continuously toward the replication fork in the 5' to 3' direction.

Lagging Strand

The DNA strand synthesized discontinuously away from the replication fork in short stretches called Okazaki fragments.

Quinolones

A class of antimicrobial drugs that specifically target bacterial Topoisomerase II (DNA gyrase) and Topoisomerase IV.

Telomeres

Noncoding repetitive sequences located at the ends of linear eukaryotic chromosomes.

Telomerase

An enzyme that attaches to telomeres to maintain chromosomal stability and integrity in eukaryotes.

Rolling Circle Replication

A specialized replication process for circular plasmids resulting in the synthesis of a single new copy of the circular DNA molecule.

Transcription

The process of copying DNA sequences into RNA (mRNA, tRNA, or rRNA) carried out by RNA polymerase.

Promoter

A specific DNA region, such as the bacterial TATA box, where RNA polymerase binds to begin transcription.

Exons

Expressed regions of eukaryotic genes that code for proteins and are retained in mature mRNA.

Introns

Intervening noncoding regions of eukaryotic pre-mRNA that are excised during processing.

Splicing

The eukaryotic RNA processing step of removing introns and joining exons together.

Codon

A triplet sequence of mRNA nucleotides that specifies a single amino acid or translation termination signal.

Anticodon

A sequence of three bases on a tRNA molecule that base-pairs with a complementary mRNA codon.

Transfer RNA (tRNA)

An RNA molecule featuring an anticodon at one end and an amino acid binding site at the other, transferring required amino acids to ribosomes during protein synthesis.

Genetic Code

The set of rules determining how each nucleotide triplet in mRNA is translated into an amino acid or stop codon.

Vertical Gene Transfer

The transfer of genetic information from parent organism to offspring, such as binary fission in prokaryotes.

Horizontal Gene Transfer

The introduction of genetic material between organisms within the same generation.

Transformation

A mechanism of horizontal gene transfer in which naked environmental DNA is taken up by a bacterial cell.

Transduction

A mechanism of horizontal gene transfer in bacteria where genes are transferred by a bacteriophage virus.

Conjugation

A mechanism of horizontal gene transfer involving transfer of DNA through direct cell contact using a conjugation pilus.

Transposition

The process whereby DNA independently excises from one location in a DNA molecule and integrates elsewhere using the enzyme transposase.

Operon

A bacterial unit of genetic organization where functional structural genes are controlled by a single promoter and operator.

Lac Operon

An inducible operon in E. coli containing three structural genes for lactose degradation, regulated by the binding and release of the lac repressor.

Point Mutation

A mutation resulting from the substitution of a single base in DNA.

Silent Mutation

A point mutation that has no effect on the final amino acid sequence of a protein.

Missense Mutation

A point mutation that results in an amino acid substitution in the synthesized protein.

Nonsense Mutation

A point mutation that substitutes a stop codon for an amino acid, causing premature protein termination.

Frameshift Mutation

A mutation caused by the insertion or deletion of one or more bases, altering the reading frame for protein synthesis.