DNA replication starts at a fixed region on the chromosome called the replication origin,
which is a sequence of about 250 base pairs.
A group of initiator proteins binds at the origin along with other enzymes, forming two
In most cases, plasmids are not essential to the normal survival of the cell but they can
confer selective advantages and provide genetic flexibility for those organisms possessing
Ex) Some bacterial plasmids, called F plasmids, allow for the tr
Protein synthesis process in which amino acids are precisely bound together in a threedimensional structure determined by the hereditary information, the genes, in the cell.
The process requires not only DNA, but also ribonucleic acid (R
Point Mutations Can be Spontaneous or Induced
Regardless of the cause of the mutation, one of the most common results is a point
mutation, which affects just one point (base pair) in a gene.
Such mutations may be a change to or substitution of a different
Mutations Are the Result of Heritable Changes in a Genome
Spontaneous mutations are heritable changes to the base sequence in the DNA that result
from natural phenomena.
Could be from everyday radiation penetrating the atmosphere or errors made and not
Transposable Genetic Elements Can Cause Mutations
Mutations of different nature may be caused by fragments of DNA called transposable
Two types known to exist in all microbial cells: insertion sequences and transposons.
DNA Polymerase Only Reads In the 3 to 5 Direction
At each replication fork the complementary DNA strand is formed in two different ways.
Leading Strand Synthesis
One parental strand in each replication factory is the template for synthesizing a
Present day microorganisms enjoy the fruits of genetic change. Because of their diverse
genes, they can thrive in the varied environments on Earth.
DNA and Chromosomes
In 1963, James Watson and Fracis Crick worked out DNAs double helix structure based,
Antibiotics Interfere with Protein Synthesis
Many antibiotics affect protein synthesis in bacterial cells and therefore are clinically
useful in treating human infections and disease.
A few antibiotics interfere with transcription.
Rifampin binds to the R
Regulatory gene codes for a repressor protein.
In the operon model, the repressor protein binds to the operator.
Binding prevents the RNA polyermase from moving down the operon and thus cannot
transcribe the structural genes.
This is called negative contr