Exam 4 Flashcards
Two types of growth in prokaryotes
Intercalary and Polar
Most common form of intercalary growth
binary fission
4 types of polar growth
- Simple Budding
- Budding by hyphae
- Cell Division in Stalked Bacteria
- Polar growth without differentiation of cell size
The growth of most microbes occurs by the process of
binary fission
What are the progeny like after the cell goes through binary fission?
The two progeny are exactly the same as the original cell
Steps in Binary Fission
- Cell Elongation
- Septum Formation (pinch b/w cells)
- Completion of Septum
- Formation of Walls
- Cell Separation
What happens to the DNA during binary fission
The DNA is copied (1 origin of replication to 2). The origins more to opposite sides of the cell and pull it apart.
Enzyme that moves the origins of replication to the opposite sides during binary fission
translocase
Steps in cell division
- DNA replication
- Formation of Divisome
- Cell elongation
proteins that ensure divisive forms at cell center
Min
proteins form ring where cell begins division
FtsZ
proteins that help hold FtsZ ring to cytoplasmic membrane
FtsA
in all 3 domains, this relaxes supercoils ahead of the replication fork
type II topoisomerase (DNA Gyrase)
in all 3 domains, this unwinds double helix at the replication form
DNA helicase
in all 3 domains, this adds RNA primer
primase
in all 3 domains, this adds deoxyribonucleotides in a 5’ to 3’ direction, complementary to the 3’ to 5’ strand
DNA polymerase (mainly DNA polymerase III)
What is the direction of synthesis in DNA replication
5’ to 3’
How is replication terminated in circular chromosomes?
Tus proteins recognize Ter sites and block the progress of the replication fork
How is replication terminated in eukaryotic chromosomes?
eukaryotes have telomerase to complete the ends of linear chromosomes to form the telomeres at each end
what happens to telomeres as you age
Telomeres get shorter as you age, but the only thing you lose is repeats
proteins that ensure divisome forms at cell center
Min
protein that forms ring were cell begins division
FtsZ
protein that helps hold ftsZ ring to cytoplasmic membrane
FtsA
proteins that form filamentous spiraled bands around inside of cell under the cytoplasmic membrane to direct new cell wall to be made at certain locations
MreB
penicillin binding proteins that are transpeptidases that insert new peptidoglycan into expanding cell wall
FtsI
proteins that are DNA translocates that move DNA during cell division
FtsK
Direction of synthesis in the replication bubble
5’ to 3’
How do bacteria and archaea terminate replication?
Circular chromosomes have Ter sites across from the origin of replication are recognized by Tus proteins that block the progress of the replication fork
sequences in the DNA where the Tus proteins bind
Ter sites
How do eukaryotes terminate replication?
Eukaryotes have telomerase to complete the ends of linear chromosomes to form the telomeres at each end
How does the MinE protein change as it moves through the cell
MinE proteins increase in concentration as it goes to the center of the cell
where does cell division take place
where the MinE protein concentration is at it’s highest
where does the FtsZ ring form
at high concentration of MinE protein
create small openings in existing cell wall
Autolysins
When may autolysis (spontaneous cell lysis) occur
if there is an error in inserting new cell wall material
steps of cell wall synthesis
- Formation of peptidoglycan precursors
- Transport of Pep. Precursors to expanding cell wall
- Insertion of peptidoglycan precursors into existing cell wall
hydrophobic lipid alcohol that binds the peptidoglycan precursor and facilitates transport through the cytoplasmic membrane
Bactoprenol
peptide bonds formation between pentapeptide of peptidoglycan precursor and tetra peptide of an existing peptidoglycan unit
Transpeptidation
what is growth?
increase in the number of cells
An example of an organism that grows through simple budding
sacharomyces
an example of a microbe that grows by budding from hyphae
hyphomicrobium
the end of the cell that begins to elongate in budding by hyphae
hypha
What are the steps in budding by hyphae?
- End of cell begins to elongate and hypha lengthens DNA replication.
- Copy of chromosomes enters bud.
- Formation of cross-septum
- Progeny that gets release has flagella
What happens when the progeny produced in budding by hyphae are ready to divide?
They will drop their flagella and follow the steps for budding by hyphae
example of a microbe that divides using the steps for cell division in stalked bacteria
caulobacter
Steps of cell division in stalked bacteria
- Loss of flagellum
- Initiation of DNA synthesis and stalk begins to grow
- Elongated stalked cell (synthesis of flagellum) and stalk attaches to a surface
- Previsional cell - cross band formation
How do eukaryotes grow?
Sexual and/or asexual reproduction
2 parents (meiosis from haploid cells (egg & sperm); fusion of haploid cells yields diploid zygote)
sexual reproduction
1 parents (mitosis keeps policy the same, so haploid yields haploid and diploid yields diploid)
asexual reproduction
What is the life cycle of Saccharomyces cerevisiae
- Budding - replication of genome
- Haploid (1n) form
- Diploid (2n) form
haploid form of saccaromyces that are germinated
ascospores
How do alpha and A strains (mating types) affect the haploid form of saccharomyces
A gives rise to more A cells
alpha gives rise to more alpha
via mitosis
When can cells of opposite mating types fuse?
Only under stress-like conditions
What is the life cycle of Chlamydomonas?
During sexual reproduction (stressful state), + and - type fuse at their flagella. Once they fully fuse together, they form a crusty outer layer (zygote, protects meiosis happening).
Why does meiosis occur in Chlamydomonas?
It occurs so that when conditions are favorable, the zygote breaks open to release the mature haploid cells