Bacterial Genetics Flashcards
All living cells maintain their genetic information in chromosomes made of double stranded DNA.
Genome- all of the genetic material in the cells of an organism.
Bacterial genome
- Code for protein: gene expression/ transcription & translation.
- Inheritance: DNA replication
- Self-regulation: turns genes on and off to maintain homeostasis for survival
Jobs of DNA
Organic macromolecules called nucleic acids.
Nucleic acids are built from nucleotides
Each nucleotide has a phosphate, sugar and base.
Constant- phosphate & sugar
Variable- base= code
DNA structure
5’ end - end with phosphate sticking end
3’ end- where new nucleotide can be added
DNA structure
Make 2 identical copies of DNA to pass to new bacterial cells (binary fission)
Semi conservative
Requires : DNA nucleotides, energetic (anabolic) and enzymes
DNA replication
enzyme called helicase unwinds DNA & splits it apart at origin of replication.
Replication process: step 1 - initiation
Results in replication bubble with a fork at each end.
There is a leading and lagging strand on each side of the bubble.
Leading end- is copied continuously
Lagging end- is copied in chunks (works backwards)
Replication process step 2
Enzyme called primase adds an RNA primer to each strand of DNA.
The leading strand only gets primed once.
The lagging strand is primed for each chunk.
Replication process step 3
Helicase continues to open DNA
DNA gyrase untangles the DNA as the fork opens
DNA polymerase adds nucleotides to the RNA primers on the 3’ of the primer
*on leading strand this occurs continuously
DNA replication : elongation
DNA polymerase 1 removes the primes and replaces them with DNA nucleotides
Elongation on lagging strand
Continues in opposite directions until the DNA polymerase runs into each other.
Comes together at termination sequence
DNA replication: termination
To express, or produce proteins that a cell needs at a given time.
A section of DNA codes for a necessary protein is copied (transcription) onto mRNA.
The code on the mRNA is translated into a protein at a ribosome with the help of tRNA.
Gene expression
RNA is necessary for gene expression:
1. mRNA is a copy for a gene/recipe card
2. rRNA folds up to make ribosomes/reading
3. tRNA carries amino acids to ribosome according to the mRNA code
Ribonucleic acid
Occurs in cytoplasm in bacteria.
Job: RNA polymerase makes a copy of expressed gene in the form of RNA.
Genes are switched on or switched off.
•the promoter region is ready to RNA polymerase when a protein coded for by that gene is needed the cell (switched on)
transcription
Location: bacterial ribosomes
Reading to make a protein
Initiation of translation
- tRNA binds to exposes codon
- New amino acid attached to polypeptide chain
- Ribsome shifts one codons over on the mRNA
Elongation of translation
Small loops of DNA with a few genes.
May enter or leave a bacterial cell without changing the species- horizontal gene transfer.
Contain small # of genes - these can include genes for toxins, antibiotic resistance
Plasmids
What are two ways bacteria generate genetic diversity?
- Random gene mutation
- Horizontal gene transfer
Random
Any changes in base sequences during DNA replication can occur
Bacteria reproduce quickly & generate these more often
can be- lethal, neutral and benefit bacteria
Mutations
Mistakes in DNA replication
Physical agents- X-rays and UV radiation
Chemical agents- mutator strains, superoxide radicals & reactive O2 molecules
Causes of mutations
- Point mutation
- Insertion/deletion
- Inversion
Types of mutations
Neutral
When a single nucleotide is changed in a DNA sequence
Point mutation
Involves the + or - of one more more molecules
Insertion/ deletion
Occurs when a fragment of DNA is flipped in orientation in relation to the DNA on other side
Inversion
