Bacterial Genetics Flashcards
Why is uracil used in RNA rather than thymine
Thymine takes more energy to be produced and since RNA is short lived, this saves the body energy and time
Define a gene
A sequence of DNA that specifies a particular protein
Define a codon
Sequence of 3 triplet code
One codon= one amino acid
Define non-sense codons
Stop codons ( ie TAA terminates synthesis of particular proteins
What is the wobble hypothesis
. The first anti codon on the tRNA is not spatially bound meaning the the first nucleotide on the tRNA can bind to 2 others rather than one
- this reduces the need for energy as less
How does the wobble hypothesis save energy
As the tRNA molecules can be used for multiple codons or uses
What can uracil on a tRNA molecule recognise
A or G
What can guanine on a tRNA molecule recognise
U or C
What are mutations
A change in the nucleotide sequence
What’s an example of a beneficial mutation
Antibiotic resistance
What is a beneficial mutation also known as
Selectable mutation (usually stable as it’s been passed down from mother cell to daughter cell
What is the wild type mutation
It’s isolated from the environment/ nature
What is a mutant type
Derived from the wild type, but caries a mutation
What are the 2 mechanisms of mutations
Spontaneous and induced
What is spontaneous mutation
Occasional random errors,
- point and frame shift
what is induced mutation
Caused by environmental factors
- radiation (x-rays, gamma rays)
-exposure to mutagens
What are some impacts of mutations
Can alter gene products
- can prevent gene function
What is point mutation
A single base pair substitution in the DNA
( can be silent, missense or nonsense
If a point mutation occurs and the result is the same amino acid what is the effect on the phenotype
There is no change
If a point mutation occurs and the result is a different amino acid what is the effect on the phenotype
Changes the phenotype
If a point mutation occurs and the results in a stop codon what is the effect on the phenotype
Changes due to the pre mature stop codon
What is a frame shift mutation
Caused by a shift in the reading frame
Explain the frame shift mutation - insertion
When a base is inserted somewhere in the sequence
Explain the frame shift mutation - deletion
When a nucleotide base is deleted from the sequence
What is the significance of mutations in bacteria
It’s what gives them their antibiotic resistance
What is horizontal gene transfer
Movement of DNA between cells that are not directly related
- DNA is incorporated into the recipient cell chromosome by recombination
- or remain independent (plasmid)
What is a plasmid
The circular piece of DNA s that Carrie’s extra genes
Define transformation
Free DNA released from one cell and is taken up by another
Define transduction
DNA transfer is mediated by a bacteriophage
Define conjugation
DNA transfer request cell to cell contact
If a cell takes up free DNA what is it then known as being
Competent
What are the main 3 steps in transformation
- Competent bacteria reversible bind DNA to their surface using a DNA binding protein
- The protein assists in the uptake of ssDNA by helping it through the gram negative membrane
- When the ssDNA enters the cell, competence specific proteins bind to the donor DNA to protect against degrading nucleases
- DNA is integrated into the recipient chromosome by recombination
Define generalised transduction
Any gene from the donor chromosome is transferred to a recipient
Define specialised transduction
Selective transfer of a small, specific section of the donor chromosome to a recipient
What are the 2 different cycles within generalised transduction
The lytic cycle and the lysogeny cycle
What are transposons
Small pieces of DNA that can move/ jump around the chromosome or transfer from bacterium
Do transposons always have a palindromic sequence its ends
Yes
