Microbial Genetics Flashcards
Genome
All genetic information about a cell
Genetic code
Set of rules that determine how a nucleotide sequence is converted to an amino acid sequence of a protein
Chromosome
Necessary
Circular
DOuble stranded
Large
DNA
Plasmids
Carry traits not necessary to survival
Circular
Double stranded
SMALL
Bacteria may have more than one
Transposons
Jumping genes
Components of nucleotides?
Nitrogen base
Pentose sugar
Phosphate group
What are nitrogen bases?
Ring of nitrogen and carbon
Very basic, having high pH
Types of nitrogen bases?
Purines (9 member double ring)
Pyrimidines (6 member single ring)
What are the 2 purines?
Adenine (A)
Guanine (G)
What are the pyrimidines?
Cytosin (C)
Thmine (T)
Uracil (8)
What are the types of pentose sugars in nucleotides?
Deoxyribonucleic acids (deoxyribose)
Ribonucleic acids (ribose)
Where are ribose and deoxyribose found in?
Ribose (RNA)
Deoxyribose (DNA)
What does the phosphate group in nucleotides contribute to?
Contributes to the overall negative charge
DNA replication: How the helix unzips steps and what happens after
- Doble helix separates as weak hydrogen bonds break in response to enzymes
- New hydrogen bonds form between new complementary nucleotides and each strand of parental template to form new base pairs
- Enzymes catalyze the formation of sugar phosphate bonds between sequential nucleotides on each resulting daughter strand
How can a cell’s DNA be changed?
Mutations during replication, vertical transfer
Horizontal Gene transfer
Mutation informatin
Permanent change in base sequence in DNA
Sometimes will cause a change in the product encoded by that gene
Spontaneous mutations occur when?
In the absence of any mutation causing agents
What are the types of mutations?
Spontaneous
Base
Nucleotide insertion/ deletion
What are the types of base substitutions(mutation)
SIlent
Missense
Nonsense
What’s a silent mutation?
Occurs when a change in sequence of nucleotide base but doesn’t change the function or amino acid
Whats a missense mutation?
When a base substitution results in a change of amino acid
What’s a nonsense mutation?
Base subsitutution results in a stop codon
TYpe of nuleotide insertion/ deletion mutation?
Frameshift
What’s a frameshift mutation?
INsertion or deletion of one or more nucleotide pairs
What are mutagens?
Agents that directly or indirectly bring about mutations
Whats the mutation rate?
Probability that a gene will mutate when a cell divides
Usually a negative exponent as they are so rare
What’s genetic recombination
Exchange of genes between 2 DNA molecules to form new combinations of genes on a chromosome
What happens if a cell picks up foreign DNA (genetic recombination)
Some of it can insert into cells chromosomes called crossing over
Some of the genes carried by chromosomes are shuffled
DNA is now recombined, meaning it has some of donors DNA
What happens in horizontal gene transfer?
Donor cell gives a portion of its DNA to recipient cell
What’s the recombinant in horizontal gene transfer?
The recipient cell that incorperates donor DNA into its own DNA
What are some ways genetic transfer can occur?
Plasmids and transposons / conjugation
Transformation
Transduction
Plasmid facts
Self replicating
Circular pieces of DNA
1 to 5% of size of chromosome
Often code for proteins that enhance the pathogenicity of a bacterum
Different types of plasmids?
F factor/ conjugative
Virulence
DISIMILATION
Col
Resistance factor
F factor plasmid fact
Carries gene for sex pili and transfer of plasmid to another cell
Virulence plasmid facts
Encode proteins that enhance pathogeniity
Disimilation plasmds
Code for enzymes that trigger catabolism
Col plasmids
Colicinogenic factor
Production of colicins
Colicins are proteins that have antibiotic activity and can kill other bacteria
R factor
Carry genes that can their host resistence to antibiotics, heavt metak, or cellular toxins
The 2 groups of R factor genes
Resistance transfer factor (genes for plasmid replication)
R determinant group (resistence genes)
Requirements for conjugation
Cell to cell contact
Must be between opposite mating types
F+ (has plasmid)
F- (does not)
Gram negative cells use what to comjugate?
Sex pilus
Comjugation steps
Donor cell attaches to recipient with pilus
Cells contact each other
One strand of plasmid Dna transfers
Recipient cell becomes F+
Limits to conjugation?
No same cells allowed will connect
Restriction enzymes
