Microbiology Chapter 11 - Mechanisms of Genes

DNA Semiconservative Replication

Results in DNA having 2 molecules | one parental strand and one new strand

Elongation

Leading strand of DNA synthesized continuously from a single primer

Lagging Strand

Leading strand of DNA synthesized discontinuously in Okazaki fragments

Telomeres

Required for eukaryotic chromosomes to protect their genes due to their linear nature

Telomerase

Extends telomeres preventing their degradation

Promoter

The DNA sequence that RNA binds to during the initiation of transcription

Exons

Coding sequences that compose eukaryotic genes that encode polypeptides 

Mutation

A heritable change in DNA

Point Mutation

Affects a single base pair | Three types

Silent Mutation

If the mRNA codon codes for the same amino acid that it intended to

Missense Mutation

If the mRNA codon codes for a different amino acid than it intended to

Nonsense Mutation

If the mRNA codon becomes a stop codon

Horizontal Gene Transfer

Important way for asexually reproducing organisms like prokaryotes to acquire new traits | aka Recombination | 3 types

Transformation

Allows for competent cells to take up naked DNA into their cytoplasm and recombine them with the host genome

Transductions

Bacteriophages carry host DNA to the next infected bacteria

Conjugation

“Fake sex” | Transfer of plasmids from one bacteria to another via sex pilus | Significant for antibiotic resistance

Operons

Prokaryotic structural genes of related function are often organized into these

Constitutive Gene | ALWAYS ON

Gene that is continuously expressed at a constant, active level | not regulated

Repressible Operon | ON AND TURNED OFF

A repressor binds to an operator, blocking the transcription of these operons | Ex. trp (Tryptophan) operon - when trp accumulates, it will eventually bind to the operator, preventing further transcription

Inducible Operon | OFF AND TURNED ON

An activator binds to an operon’s regulatory region, enhancing transcription. | An inducer will influence transcription as well. | Ex. lac (Lactose) - when lactose is present in cell, it gets converted into Allolactose (its inducer), which will bind to the repressor and prevent it from binding to an operator, enabling transcription and translation

Operator

DNA sequence where a repressor can bind to - if bound together, they will block the RNA polymerase from initiating transcription and thus translation (aka no protein production)