Exam 2 Flashcards
Three stages of translation
Initation, elongation, termination
Initiation
The ribosome attaches to the mRNA
The ribosome finds the start codon
The ribosome binds to the first tRNA, which carries the amino acid methionine
An initiation complex forms
Elongation
The ribosome moves along the mRNA
Amino acids are added to the growing protein chain
Peptide bonds form between the amino acids
Termination
The ribosome reaches a stop codon (UAA, UAG, or UGA)
The ribosome releases the polypeptide
The translation complex breaks apart
Mutation (occurs in members of all domains)
Heritable change in DNA sequence
– Can generate alleles (alternate forms of genes)
– Can give rise to new phenotypes
Vertical gene transfer (Eukarya)
Sexual reproduction
– New combinations of genes when gametes
from parents fuse
Horizontal Gene Transfer
Transfer from one independent organism to
another
Bacteria and Archaea are prokaryotic and
they don’t reproduce sexually.
Only a few bacterial genera known to be naturally
competent:
- Gram + Streptococcus, Bacillus
- Gram - Haemophilus, Neisseria, Acinetobacter
Competent bacteria have
membrane-bound protein
complexes that bring DNA into the cell.
Artificial Transformation
In cloning protocols, artificial transformation is used to introduce recombinant DNA into host bacteria not competent
Horizontal Gene Transfer
Requires pili, plasmids
– The F (Fertility) Factor of
E. coli is a well-studied
conjugative plasmid
– Some conjugative
plasmids, called R
factors, encode
resistance to antibiotics
Causes crown gall (tumor)
disease
Agrobacterium tumefaciens
Agrobacterium - Plant Cell Interaction
To activate genes for T DNA transfer, Agrobacterium
senses compounds released by wounded plants
through a protein complex called VirA on its cell membrane, which acts as a receptor to detect these signals and then triggers the activation of “vir” genes.
