Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
74 Cards in this Set
- Front
- Back
|
Which families are considered prokaryotes?
|
*bacteria
archaea |
|
|
What do prokaryotes lack that eukaryotes do not?
|
nuclear membrane
|
|
|
Bacteria ______________ all other organisms on Earth.
|
outnumber
|
|
|
What is the size range of bacteria in length?
|
200 nanometers - 500 micrometers
|
|
|
What is the habitat range for bacteria?
|
land, aquatic, parasitic
Their remarkable metabolic diversity allows them to live almost anywhere. |
|
|
What are the common features of bacteria?
|
lack nuclear membrane
lack membrane bound organelles (chloroplasts and mitochondria) chromosome folds to form a nucleoid body most have a cell wall some have a mucuslike coating called a capsule that helps them resist attack by the immune system many move by flagella, which propel them toward food or light |
|
|
In bacteria, there is usually only one circular chromosome meaning that it is ______________.
|
haploid --> carry one copy of each gene
|
|
|
How does bacteria condense?
|
by supercoiling and looping into a densely packed nucleoid body
|
|
|
How do bacteria replicated?
|
inside cell and cell divides by binary fission
|
|
|
Being that bacteria are haploid, this means that mutations are always __________________.
|
homozygous
Therefore, all mutations express their phenotype. |
|
|
Because of their metabolic diversity, bacteria play essential roles in many natural processes such as...
|
the decomposition of materials essential for nutrient cycling
|
|
|
Mutations in bacteria can change colony morphology, affecting what characteristics of a colony?
|
whether a colony is large or small, shiny or dull, round or irregular
|
|
|
Mutations in bacteria can confer resistance to bactericidal agents such as ________________ or ____________________.
|
antibiotics or bacteriophages
|
|
|
Mutations in bacteria that create auxotrophs (unable to grow on minimal medium) occur in genes encoding enzymes required to synthesize relatively complex compounds such as __________________ or ______________________ from simpler materials in the environment.
|
amino acids or nucleotide components
|
|
|
Mutations in bacteria can affect the ability of cells to break down and use specific _____________ in the environment.
|
chemicals
|
|
|
Mutations in bacteria can silence essential genes whose protein products are required for ____________.
|
growth
|
|
|
How do researchers identify mutations in bacteria?
|
genetic screen --> an examination of each colony in a population for its phenotype
|
|
|
Where is bacteria grown in a lab? What is the most common bacteria to be grown in a lab?
|
Bacteria is grown in liquid or on a petri dish.
The most common bacteria is E.coli |
|
|
What is one advantage of bacteria that has made it so attractive for genetic studies?
|
the ability to grow large numbers of cells
|
|
|
How quickly do bacteria multiply in liquid media? In agar media?
|
E. coli grow to a concentration of 10^9 cells per milliliter per day in liquid media.
E. coli will multiply to a visible colony containing 10^7 or 10^8 cells per milliliter in less than a day in agar media. |
|
|
Describe E. coli.
|
inhabitant of intestines in warm blooded animals
can grow in the absence of oxygen strains used in lab are not pathogenic, but other strains can cause a variety of intestinal diseases prototrophic - makes all the enzymes it needs for amino acid and nucleotide synthesis grows on minimal media containing only one carbon and energy source (glucose) divides about every 20 minutes to produce 72 generations a day rapid multiplication make it easy to observe very rare genetic events |
|
|
In E. coli, there is almost no _________________.
|
repetitive DNA
|
|
|
Close to 90% of E. coli DNA encodes proteins. This contrasts with the human genome, in which less than 5% of DNA encodes proteins. What is the reason for this discrepancy?
|
E. coli genes have no introns and there is very little repeated DNA in bacteria.
|
|
|
What is the largest class in the E. coli genome?
|
the 427 genes with the transport function
4288 genes total; 40% of genes have unknown function |
|
|
In DNA replication in E. coli, there is ________ origin of replication.
|
one (oriC)
|
|
|
What is the term that describes small transposable elements that dot the chromosomes of many types of bacteria and do not contain selectable markers?
|
insertion sequence (IS) elements
|
|
|
Describe the ends of insertion sequence (IS) elements.
|
inverted repeats
Each IS includes a gene encoding transposase that initiates transposition by recognizing these mirror-image ends. (Ends indicate where insertion sequences can insert themselves into the gene). |
|
|
Why can the distribution of insertion sequences cause bacterial strains to differ?
|
because insertion sequence elements can move to other sites on the bacterial chromosome
|
|
|
What is a common result of IS transposition into a gene in E. coli? How?
|
many spontaneous mutations
When an IS transposes and lands within the codon region of a gene, it disrupts the coding region and inactivates the gene. |
|
|
What is the term that describes smaller circles of double stranded DNA that are not needed for reproduction or normal growth of bacteria?
|
plasmid
|
|
|
Plasmids carry genes not normally needed by their bacterial hosts for growth and reproduction, but they same genes may be ____________________.
|
beneficial
|
|
|
Plasmids can carry genes that:
|
confer resistance to antibiotics and toxic substances
cause pathogenicity |
|
|
Plasmids can be transferred from one bacterium to another, sometimes even across a species. This makes plasmids have terrifying implications for _____________________.
|
medicine
|
|
|
What occurs if resistance plasmids are transferred to new strains of pathogenic bacteria?
|
the new hosts acquire resistance to many antibiotics in a single step
|
|
|
What is vertical gene transfer?
|
occurs from one generation to the next and is particularly important in organisms utilizing sexual reproduction
|
|
|
What is lateral gene transfer (horizontal gene transfer)?
|
the traits involved are not transferred by inheritance from parents to offspring; rather they are introduced from unrelated individuals or from different species
|
|
|
Bacteria can transfer genes from one strain to another through three different mechanisms: transformation, conjugation, and transduction.
In all 3 mechanisms, the ____________ provides the genetic material for transfer, while the ________________ receives the material. |
The DONOR provides the genetic material for transfer, while the RECIPIENT receives the material.
|
|
|
Describe transformation.
|
DNA from a donor cell is added to the bacterial growth medium and is then taken up from that medium by the recipient.
|
|
|
Describe conjugation.
|
The donor carries a special type of plasmid that allows it to come in contact with the recipient and transfer DNA directly.
|
|
|
Describe transduction.
|
The donor DNA is packaged within the protein of a bacteriophage and transferred to the recipient when the phage particle infects it.
|
|
|
In transformation, fragments of donor DNA released into the medium enter the ____________________ and...
|
recipient cell and alter the genotype
|
|
|
Cells that take up foreign pieces are said to be ______________.
|
competent --> able to take up DNA from the medium
The goal of transformation is to achieve competence. |
|
|
Cells can be competent naturally, or can be made competent through artificial transformation. Describe.
|
The cells are suspended in a high concentration of calcium at cold temperature. Under these conditions, the cells become permeable to single and double stranded DNA.
OR electroporation - researchers mix a suspension recipient bacteria with donor DNA and then subject the mixture to a very brief high-voltage shock. The shock causes holes to form in the membrane, which allows the cells to take up the DNA very efficiently. |
|
|
Describe natural transformation.
|
One strand of a fragment of donor DNA enters the recipient, while the other strand is degraded.
The entering strand recombines with the recipient chromosome, producing a transformant when the recipient cell divides. |
|
|
How is DNA transferred in conjugation?
|
A donor cell transfers DNA directly to the recipient. This is initiated by conjugative plasmids in donor strains.
Many different plasmids can initiate conjugation because they carry genes that allow them to transfer themselves to the recipient. |
|
|
What is the F plasmid?
|
first conjugative plasmid discovered
carries many genes required for the transfer of DNA Cells carrying an F plasmid are called F+ cells, without it F- cells |
|
|
Because they lack F factors, F- cells cannot make ____________.
|
pili
|
|
|
What is the term that describes the hollow protein tube that protrudes from a F+ (or Hfr, or F' cell) and binds to the cell wall of the F- cell?
|
pilus
|
|
|
Retraction of the pilus into the F+ cell draws what two cells together?
|
F+ and F- together to prepare for gene transfer.
|
|
|
In the original F+ cell, newly synthesized DNA replaces the single strand transferred to the F- cell. What occurs when the two bacteria separate at the completion of DNA transfer and synthesis?
|
When the F+ (male cell) and F- (female cell) separate at the completion of DNA transfer and synthesis, they are both F+.
|
|
|
Why are F+ cells thought of as male bacteria?
|
because the cells can transfer genes to other bacteria
|
|
|
If F-plasmid is in the bacterial chromosome, which mechanism for gene transfer will take place?
|
conjugation --> lateral gene transfer
|
|
|
Cells whose chromosome carry an integrated plasmid are called Hfr bacteria, because..
|
they produce a High Frequency of recombinants for chromosomal genes in mating experiments with F-strains.
In this case, DNA is frequently transferred with pieces of the F plasmid DNA --> lateral transfer |
|
|
The transfer of DNA from an Hfr cell mated to an F- cell starts with a single-strand nick in the middle of the integrated F plasmid at the ______________________.
|
origin of transfer
|
|
|
How is the second strand of DNA in conjugation produced?
|
rolling circle mechanism --> one strand is nicked and the free 3' OH is extended by the DNA polymerase
|
|
|
What characteristics do insertion sequence elements and DNA transposons have in common?
|
They can jump into genes, relocate genes, and carry transposase.
|
|
|
Where are genes that are actively transcribed during DNA replication located?
|
near oriC (origin of replication)
|
|
|
Where are genes with lower gene expression located?
|
closer to termination during chromosomal replication
|
|
|
How do bacteria transfer genes?
|
horizontal (lateral) gene transfer
|
|
|
In transduction, a ____________ transfers DNA from a donor to a recipient.
|
bacteriophage --> virus that uses bacteria as a host
|
|
|
What occurs when a bacteriophage injects its DNA into a bacterial cell?
|
the phage DNA takes over the cell's protein synthesis and DNA replication machinery, forcing it to express the phage genes, produce phage proteins, and replicate the phage DNA
The newly produced phage DNA bursts (lyses), releasing 100-200 new viral particles ready to infect other cells. |
|
|
Bacteriophages can be _____________ or ______________.
|
virulent or temperate
|
|
|
A virulent bacteriophage has a _____________ life cycle. Describe specific life cycle.
|
lytic = the cycle resulting in cell lysis and release of progeny phage
|
|
|
A temperate bacteriophage has a _____________ life cycle. Describe specific life cycle.
|
lytic or lysogenic (usually start lysogenic and lysis can be triggered later)
lysogenic = DNA integrates into the host genome and multiplies along with it, doing little or no harm to the host. The integrated copy of the temperate bacteriophage is called a prophage. lytic = the cycle resulting in cell lysis and release of progeny phage |
|
|
What affects the choice or lifestyle of temperate bacteriophage (lytic or lysogenic)?
|
environmental conditions
|
|
|
During the lytic life cycle, some pieces of the host chromosome (instead of viral DNA) are packaged into ____________________________.
|
new virus particles and are released
|
|
|
What is the transfer of DNA via a bacteriophage?
|
transduction
|
|
|
Normal prophage excision = generalized transduction, while abnormal prohage excision = _________________.
|
specialized transduction
|
|
|
What are the differences in specialized and generalized transduction?
|
Generalized transducing phages pick up donor DNA during the lytic cycle, while specialized transducing phages pick up donor DNA during the transition from lysogenic to lytic cycle.
Generalized transducing phages can transfer any bacterial gene or set of genes contained in the right size DNA fragment into the bacterial chromosome, while specialized can transfer just those genes near the site where the bacteriophage inserted into the bacterial genome. |
|
|
In a normal excision, what action does prophage take?
|
Prophage pops out and gets the cell to replicate more DNA.
|
|
|
In an abnormal excision, what action does prophage take?
|
Part of the bacteria pops out along with the prophage.
|
|
|
What are knock-out mutants and what are the two ways to create knock-out mutants?
|
Knock out mutants destroy a gene.
transposons - can jump into a gene and damage/destroy it plasmids - can target specific known gene sequences and destroy function (reverse genetics); aren't as easy to work with |
|
|
Reverse genetics provides a way to insert ______________ genes to test function.
|
synthetic
recombineering --> a mutant version of the gene is constructed in vitro (not in a cell) and then introduced into a cell. Then in vivo recombination inserts the constructed gene into the chromosome in place of the wild-type copy. |
|
|
What is an effective way to create a defective allele or knock-out mutation?
|
insertion of an antibiotic resistance gene
|
