Chapter 9 Flashcards
(19 cards)
conjugation
takes place when genetic material passes directly from one bacterium to another
transformation
when a bacterium takes up DNA from the medium in which it is growing
transduction
takes place when bacterial viruses carry DNA from one bacterium to another
- bacterial genes incorporated into phage coats and transferred to other bacteria by phased
which process of DNA transfer in bacteria requires a virus?
transduction
what did lederberg and Tatum demonstrate?
that bacteria can transfer and recombine genetic information
cells that can take up DNA through their cell membranes are said to be
competent
What does cotransformation and relative rates
the higher the rate of cotransformation, the closer the genes are on the bacterial chromosome
horizontal gene transfer
genes can be passed between individual members of different species by nonreproductive mecahnsims
restriction-modification systems
bacteria produce enzymes called restriction endonucleases that recognize and cleave double stranded DNA at specific nucleotide sequences
CRISPR-CAS systems
combine small RNA molecules known as CRISPR RNA with CAS proteins to provide defense against specific foreign DNA molecules originating from viruses,
what do the CRISPR-cas systems contain
- DNA sequence called CRISPR array
- set of genes encoding proteins
CRISPR array
- located in bacterial/archaeal chromosome and consists of a series of repeated DNA sequences called clustered regularly interspaced short palindromic repeats
palindromic sequences
sequences that read the sequences that read the same forward and backward on two complementary DNA STARANDS
CAS proteins
essential to functioning CRISPR-Cas systems
How does CRISPR-cas system function
Adaptation- when foreign DNA from a virus, plasmid or other element enters the cell
- foreign DNA is identified and cleaved by Cas proteins into protospacers
- protospacers are then processed into CRISPR array as spacers which serve as a memory of foreign DNA
second stage of CRISP
- CRISPR array is transcribed into a long CRISPR precursor RNA and cleaved by cas proteins and processed into crna’s
- combines with a CAS PROTEIN TO FORM AN EFFECTOR COMPLEX
what happens in the final stage of CRISPR
interference- foreign DNA from the same plasmid enters cell
- effector complex binds to foreign DNA through base pairing between cRNA and foreign DNA sequences
- cas protein cleaves foreign DNA which is degraded
oncogenes
may stimulate cell division and cause the formation of tumors
