Microbial Genetics - Lecture Notes

Vocabulary practice flashcards covering fundamental concepts, enzymes, and mechanisms of microbial genetics, including DNA structure, replication, transcription, and translation.

Genetics

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

Chromosomes

Structures containing DNA that physically carry hereditary information; the chromosomes contain genes.

Genes

Segments of DNA that encode functional products, usually proteins.

Genome

All the genetic information in a cell.

Genetic code

A set of rules that determines how a nucleotide sequence is converted to an amino acid sequence of a protein.

Genotype

The genetic makeup of an organism.

Phenotype

The expression of the genes of an organism.

Vertical gene transfer

The flow of genetic information from one generation to the next.

Horizontal gene transfer

The flow of genetic information within the same generation.

DNA Gyrase

An enzyme that relaxes supercoiling ahead of the replication fork.

DNA Ligase

An enzyme that makes covalent bonds to join DNA strands, Okazaki fragments, and new segments in excision repair.

DNA Polymerases

Enzymes that synthesize DNA, proofread, and repair DNA in the $5' \rightarrow 3'$ direction.

Helicase

An enzyme that unwinds double-stranded DNA.

Primase

An RNA polymerase that makes RNA primers from a DNA template.

Endonucleases

Enzymes that cut the DNA backbone in a strand of DNA to facilitate repair and insertions.

Exonucleases

Enzymes that cut DNA from an exposed end of DNA to facilitate repair.

Methylase

An enzyme that adds a methyl group to selected bases in newly made DNA.

Photolyase

An enzyme that uses visible light energy to separate UV-induced pyrimidine dimers.

Ribozyme

An RNA enzyme that removes introns and splices exons together.

RNA Polymerase

An enzyme that copies RNA from a DNA template.

snRNP

An RNA-protein complex that removes introns and splices exons together.

Topoisomerase

An enzyme that relaxes supercoiling ahead of the replication fork and separates DNA circles at the end of DNA replication.

Transposase

An enzyme that cuts the DNA backbone, leaving single-stranded "sticky ends".

Leading strand

The DNA strand that is synthesized continuously by DNA polymerase during DNA replication.

Lagging strand

The DNA strand that is synthesized discontinuously as Okazaki fragments during DNA replication.

Okazaki fragments

Short, discontinuous DNA fragments synthesized on the lagging strand that are later joined by DNA polymerase and DNA ligase.

Transcription

The synthesis of a complementary mRNA strand from a DNA template.

Promoter

The specific sequence on DNA where RNA polymerase binds to initiate transcription.

Terminator

The sequence on DNA where transcription stops and RNA polymerase is released.

Translation

The process where mRNA is translated into the "language" of proteins.

Codons

Groups of three mRNA nucleotides that code for a particular amino acid.

Sense codons

The 61 mRNA codons that encode the 20 amino acids.

Degeneracy

The property of the genetic code where each amino acid is coded by several different codons.

Start codon

The codon AUG where the translation of mRNA begins, coding for methionine.

Nonsense codons

The three stop codons (UAA, UAG, UGA) where translation ends.

Anticodon

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

P site

The site on the assembled ribosome where the tRNA carrying the first amino acid or growing polypeptide chain sits.

A site

The site on the ribosome where a tRNA carrying the incoming amino acid pairs with the corresponding codon on the mRNA.

E site

The exit site on the ribosome occupied by an uncharged tRNA before it is released.

Polysome

A complex formed by a number of ribosomes translating the same mRNA transcript sequentially; also called a polyribosome.