cht 8 Flashcards
How is it that Bacteria are such dynamic
organisms
-They have relatively short generation times
-Genetic changes may be rapidly incorporated into the
population
-Easily transported to new environments
- endosymbionts
-Horizontal Gene Transfer
Structure of Prokaryotic Genomes
-Main portion of DNA, along with associated proteins
and RNA
- Prokaryotic cells are haploid
-Typical chromosome is a circular molecule
Structure of Eukaryotic Genomes
- Typically have more than one chromosome per cell
- Chromosomes are linear and sequestered within
nucleus - Linear chromosomes are wrapped around core histone
proteins to form chromatin
-Eukaryotic cells are often diploid
What are the advantages and disadvantages
of Circular chromosomes
Very efficient
- No telomeres (ends of linear chromosomes)
- No core histone proteins needed
- Cell division is quicker and less complicated
con
Cannot get as large as linear chromosomes (fewer
genes present)
Plasmids
are self-replicating circular pieces of
DNA
-Often code for proteins that enhance the
pathogenicity of a bacterium
-Not essential for normal metabolism, growth, or
reproduction
* Can confer survival advantages
* Many types of plasmids:
- Fertility factors (conjugation pilus)
- Resistance factors (antibiotic resistance genes)
- Bacteriocin factors (produce antimicrobial peptides)
- Virulence plasmids (capsules, exotoxins)
Chromosomes
structures containing DNA that
physically carry hereditary information; the
chromosomes contain genes
Genes
segments of DNA that encode functional
products
Genome
all the genetic information in a cell
Vertical gene transfer
parents to offspring
DNA Replication
One strand serves as a template for the
production of a second strand
* Topoisomerase and gyrase relax the strands
* Helicase separates the strands
* A replication fork is created
DNA polymerase removes RNA primers;
Transcription
A gene usually has a promoter region, a
transcribed region, and a termination region.
Ribosomal RNA (rRNA)
integral part of
ribosomes
Transfer RNA (tRNA)
transports amino acids
during protein synthesis
Messenger RNA (mRNA)
carries coded
information from DNA to ribosomes
Proteins
enzymes,
structures, defense, transport molecules,
receptors, membrane channels, etc
