Transcript Genetic Variation in Prokaryotes

Genetic Variation in Prokaryotes
AP Biology
Chapter 27
Recall: Bacterial Structure
• Prokaryotic cells
– Lack nuclei
– Lack membranebound organelles
(have ribosomes for
protein synthesis)
– May have flagella for
movement
– May have capsule
around cell wall
– Various shapes,
arrangements
Bacterial Genetics
• Single, circular bacterial
chromosome in nucleoid
region
• Often contain one or
multiple plasmids
– “Bonus” genes
independent of bacterial
chromosome
– Code for traits such as
antibiotic resistance,
fertility factors
Bacterial Variation
• Even though bacteria are
asexual, they are not clones!
• Variation introduced by:
– Mutations
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Chromosome and/or plasmid
replication
Transformation
Transduction
Conjugation
Transposable
elements/transposons
Mutations
• Changes in DNA during replication
• Grow and divide FAST, so errors happen
and get passed on quickly
• Ex: drug resistant bacteria
Transformation
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Alteration of a bacterial cell’s genotype
and phenotype by the uptake of naked,
foreign DNA from the surrounding
environment
Ex: harmless Streptococcus pneumoniae
bacteria can be transformed to
pneumonia-causing cells
Transduction
• Phages carry bacterial genes
from one host cell to
another
• Generalized transduction –
random genes are
transferred
• Specialized transduction –
genes adjacent to prophage
site in temperate phages
Conjugation
• The direct transfer of genetic material
between cells
• Bacterial ‘sex’
Transposons
• Transposable genetic
elements
– “jumping genes”
• Pieces of DNA that
move around within
the genome