L2 Introduction to Bacterial Genetics Flashcards
Understand basic concepts, techniques and key terms in bacterial genetics.
DNA is arranged in a double helix structure, with the two strands ? to one another.
Antiparallel (parallel, but going in opposite directions)
Define: Wildtype
An unmodified natural isolate of a species (e.g. that which is used for comparative experimental purposes)
Define: Mutant
A variant from the wild type as a result of a specific change in the DNA sequence (see Mutation)
Define: Mutation
A specific change in the DNA sequence of an organism (such that the sequence differs from the wildtype)
Define: Allele
One copy of a gene
Define: Phenotype
An observable trait that may be altered by genetic mutation
Define: Genotype
The defined nucleotide sequence of an organism, usually expressed in terms of alleles of its genes
Define: Haploid
Possessing a single copy of each gene
Define: Diploid
Possessing two copies of each gene
Define: Polyploid
Possessing multiple (more than 2) copies of each gene
When a cell is ‘competent’, this means ? is able to occur
Transformation (genetic alteration of a cell resulting from uptake of exogenous genetic material)
The transfer of genes by direct cell-to-cell contact is known as…
Conjugation
Conjugation involves a donor and a recipient. It is usually mediated by…
Conjugative plasmids
In the lab, the Hfr strain allows conjugation to transfer part of the…
Chromosome itself (not just the plasmid)
Non-conjugative plasmids lack which gene?
mob gene
Transduction involves the use of a ? to introduce exogenous DNA
Bacteriophage (phage)
Describe the polarity of dsDNA and the group present at each end
5’ and 3’ ends are reversed between strands. PO4 at 5’, OH at 3’
The ‘Central Dogma’ of genetics states that…
Information, once encoded in a protein, cannot be decoded back into RNA or DNA ⏮
Transcription can be described in 3 stages…
- Initiation
- Elongation
- Termination
DNA synthesis is…
Semi-Conservative ½
DNA synthesis in bacteria requires an…
RNA (or DNA) primer
dNTP is the DNA precursor, more specifically the 4 types (corresponding to the different bases) are…
- dATP (adenine)
- dGTP (guanine)
- dCTP (cytosine)
- dTTP (thymine)
Bacterial chromosomes are ? shaped
Circle ⃝
When DNA is synthesised from the bacterial chromosome, there are two…
Replication forks
When DNA synthesis occurs, there are key differences between the two strands, which are known as the…
Leading and lagging strands
Mutations are sometimes detectable by phenotype. If not, we can use…
Sequence analysis
A transition mutation results in a change from one type of base…
to another base of the same type (e.g. Pyrimidine to Pyrimidine ( C ⃡ T ) / Purine to Purine ( A ⃡ G )
A transversion mutation results in a change from one type of base…
to another base of a different type (e.g. Pyrimidine (C or T) to Purine (A or G) and vice versa)
Mutations can be (4 types)…
- Silent
- Missense
- Nonsense
- Frameshift
A change in the base on position 3 often causes a ? mutation
Silent
The more genes are required for a particular phenotype…
The more likely a mutation is to occur (and to have an observable effect)
Spontaneous mutations are very rare, partly due to the…
Powerful repair systems in cells
Mutagens can be used to artificially overload cell repair mechanisms. This is known as…
Induced Mutation
Selection of mutations from cultures is either…
General or specific
Describe 3 ways of selecting mutant bacteria…
- ❌ Negative selection (select for mutants which have lost certain capabilities, uses the velvet pad)
- 💊Enrichment (prevent growth of mutants, eliminate growing wildtypes with antibiotics)
- ✅ Positive selection (provide conditions where only the mutants will grow)
