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Chapter Nine (quiz six)
Microbial Genetics
59
Microbiology
Undergraduate 2
03/08/2013

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Term
What must happen to proteins before it is released from the ribosome
Definition
It must fold upon itself to achieve its biologically achieve tertiary
conformation
Posttranslational modifications may be necessary
- starting amino acids cut off
- cofactors added
- join with other proteins to form quaternary levels of structures
Term
Processing gene information in prokaryotes?
Definition
- mRNA can assiocate with ribosomes in the cytoplasm as the mRNA is being formed
- translation of mRNA into proteins can begin before transcription is complete
Term
What is an operon?
Definition
individual mRNA molecules often contain transcripts for several genes. By placing genes with similar functions on the same mRNA, bacteria coordinate the synthesis of these proteins. These clustered genes are referred to as operons.
Term
Eukaryotic mRNA's code for how many proteins?
Definition
just one
Term
Can eukaryotic transcription and translation occur at the same time?
Definition
nope because the DNA is in the nucleus, it must occur in different compartments
Term
What do eukaryotic DNA often have?
Definition
Introns! these must be removed before translation
Term
What make up split genes?
Definition
introns and exons
Term
Introns?
Definition
sequences of bases that do not code for protein
Term
exons?
Definition
coding regions that will be translated into protein
Term
What percent of DNA do introns make up?
Definition
98%
Term
How is the nucleic acid arranged in virus
Definition
usually linear but can also be circular
Term
How is the genome arranged in viruses?
Definition
usually a single molecules, but can also be segmented into several peices
Term
Info about animal viruses
Definition
-viral nucleic acid penetrates the cell
-nucleic acid penetrates the cell
- the virus instructs the host's machinery to synthesize large numbers of new virus particles
- viral mRNA is translated into viral proteins on host cell ribosomes using host tRNA
Term
Inductible operons
Definition
the operons is turned on by the substrate of the enzyme for which the structural genes code (positive feedback)
Term
repressible operons
Definition
contain genes coding for anabolic enzymes; several genes in a series are turned off by the product synthesized by the enzyme (negative feedback)
Term
An inducible operon is kept "off" by...?
Definition
the repressor
Term
What does the substrate act as for an incucible operon?
Definition
an inducer! it blocks the action of the repressor, allowing the operon to be "on"
Term
Example of Incucible Operon
Definition
lac operon in E.coli
Term
What is the regulator in Lac Opreon
Definition
a gene that codes for a protein capable of repressing the operon, which is the repressor
Term
What are the control locus feature of Lac operon
Definition
Promoter: recognized by RNA polymerase
Operator: a sequence that acts as an on/off switch for transcription
Term
Structural Locus feature in Lac opreon
Definition
three genes each coding for a different enzyme needed to catabolize lactose
Term
Co-repressor in repressible operon
Definition
excess nutrient serves as this, it is needed to block the action of the operon
Term
Example of repressible operon
Definition
Arg operon
Term
phase variation?
Definition
through this, the bacterium can induce or repress the expression of a set of genes and change its phenotype
-turn on and off particular genes
Term
What is a mutation?
Definition
a change in nucleotide sequence (ATCG)
Term
What is a wild-type?
Definition
a microorganism that exhibits a natural, non-mutated characteristic
Term
what is a mutant strain?
Definition
when a microorganism bears a mutation
Term
Spontaneous mutation
Definition
random change in the DNA arising from errors in replication
-random
Term
Induced mutation
Definition
results from exposure to know mutagens
ex: ultraviolet radiation
Term
Two categories of mutagenic agents
Definition
chemical or radiation
Term
Two categories of Mutations
Definition
point or frameshift
Term
Point mutations
Definition
involve addition, deletion or substitution of single bases
Term
Frameshift mutations
Definition
when one ot more bases are inserted into or deleted from a newly synthesized DNA strand
-changes the reading frame of the mRNA
-nearly always results in a nonfunctional protein
Term
Point-mutation submutation:
Missense mutation
Definition
results in different amino acid
Term
Point-mutation submutation:
Nonsense mutation
Definition
results in a premature stop codon
Term
Point-mutation submutation:
Silent mutation
Definition
no effect
Term
Point-mutation submutation:
Back-mutation
Definition
second mutation corrects effect of first
Term
Random mutation info
Definition
mutation are permanent and inheritable
most are harmful but some provide adaptive advantages
Term
Recombination
Definition
when one bacterium donates DNA to another bacterium
Term
What is the end result of recombination?
Definition
a new strain different from both the donor and the original recipient
Term
What are easily exchanged among bacteria
Definition
plasmids!
Term
recombinant organism
Definition
any organism that contains (and expresses) genes that originated in another organism
Term
Difference between plasmid and chromosomal fragments mode of transmission of genetic material in bacteria
Definition
-plasmid can replicate independently of the bacterial chromosomes
-chromosomal fragments must integrate themselves into the bacterial chromosome in order to replicate
Term
What are the 3 means of recombination in bacteria
Definition
1. Conjugation
2. transformation
3. transduction
Term
Conjugation-- factors involved
Definition
-donor cell with pilus
-fertility plasmid in donor
-both donor and recipient are alive
-bridge forms between cells to transfer DNA
Term
Conjugation-- Direct or indirect?
Definition
direct!
Term
Transformation-- factors involved?
Definition
-free donor DNA (fragment)
-live, competent recipient cell
Term
Transformation-- direct or indirect?
Definition
indirect!
Term
Transduction-- factors involved?
Definition
-donor is lysed bacteria cell
-defective bacteriophage is carrier of donor cell
-live recipient cell of same species as donor
Term
Transduction-- direct or indirect?
Definition
indirect
Term
What is a pilus?
Definition
cytoplamic bridge that lets two cells dock and transfer materials between them
Term
Stains of bacteria containing/and not the f factor
Definition
F+ and F-
Term
Resistance Plasmids?
Definition
bear genes for resisting antibiotics
-can confer multiple resistance to antibiotics to a strain of bacteria
Term
HFR stains
Definition
-the f factor is integrated into the chromosome
-the copied chromosome will contain the f factor and chromosomal genes
- recipient cell is now an Hfr with new henes
Term
Transfermation is what?
Definition
capturing DNA from solution
- it is nonspecific acceptance of foreign DNA by a bacterial cell
Term
What are competent cells?
Definition
they are capable of accepting genetic material (the live cell)
Term
What is generalized transduction?
Definition
It involves a lytic bacteriophage

-during bacteriophage assembly, some bacterial host DNA is packaged into capsid with viral DNA
Term
What is specialized transduction?
Definition
-involves lysogenic bacteriophage
transfer of only a few specific genes from one bacterial cell to another by means of a phage
Term
What are transposons?
Definition
jumping genes
-they move from place to place in the genome, plasmids, and viral genomes
-they disrupt the place they land
-they mobilize other genes (like antibiotic resistance
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