1.6 S Phase and Mitosis Flashcards
Before mitosis can proceed, DNA must be [ ].
replicated
It is important that the genome be replicated only [ ] per cell cycle.
once
In eukaryotes, DNA replication begins at multiple [ ], which are distributed throughout the genome.
origins of replication
For DNA replication to begin, the DNA must first be [ ] at the OR by [ ].
- unwound
- helicase enzymes
- Either late in mitosis or in early G1, DNA is bound by [ ] at each OR.
- This is called [ ] of ORs.
- DNA replicaion is only permitted at ORs preloaded with [ ].
- two inactive Mcm helicases
- “licensing”
- Mcm helicase
In S Phase, [ ] activates Mcm helicases.
S-cdk
Mcm will only occur when [ ].
new inactive Mcm helicases are loaded in late mitosis or G1.
The OR is bound by the [ ].
origin recognition complex (ORC)
In late mitosis or early G1, [ ] and [ ] work together to recruit Mcm helicase to the ORC.
- Cdc6
- Ctd1
With the help of [ ], S-Cdk activates Mcm helicase, leading to [ ] and binding of [ ].
- accessory proteins
- unwinding of DNA
- replication machinery
In late mitosis, [ ] promotes inactivation of Cdks.
APC/C
Following APC/C, [ ] and [ ] are inactivated (dephosphorylated). This allows for McM helicase to [ ].
- ORC
- Cdc6
- reload
Genome replication requires [ ].
chromatin replication
The production of chromatin proteins also increases during [ ].
S phase
S-Cdks promote the synthesis of [ ] which ultimately become a histone octamer known as the [ ].
- the four histone subunits
- nucleosome
Chromatin structure around the newly synthesized DNA must [ ].
match that of the original chromosome
Newly replicated “chromosomes” remain [ ] to the original chromosome, known as [ ].
sister chromatids
What are cohesins?
a large protein that forms a ring around the sister chromatids, and is reponsible for linking them together
[ ] is a complex of 4 subunits. Two subunits from from the [ ] family of proteins. The other two subunits ([ ] and [ ]) complete the tetramer.
- Cohesin
- SMC
- Scc1
- Scc3
M phase of the cell cycle begins with [ ]. In this process, sister chromatids will be divided into [ ], becoming separate chromosomes in the process.
- mitosis
- two daughter nuclei
What are the five stages of mitosis?
prophase, prometaphase, metaphase, anaphase, and telophase
In prohphase, sister chromatids [ ] inside the nucleus. Outside of the nucleus, the [ ] forms between two centrosomes.
- condense
- mitotic spindles
In prometaphase, the [ ] breaks down. This allows [ ] to attach to the [ ].
- nuclear envelope
- chromatids
- mitotic spindle, and initiate movement
During metaphase, sister chromatids haev now aligned at the [ ].
spindle equator
In anaphase, the chromatids are pulled towards their [ ], becoming [ ]. Both the microtubules get [ ], and [ ] move apart.
- spindle poles
- daughter chromosomes
- shorter
- spindle poles
In telophase, [ ] reach the spindle poles and [ ]. A new [ ] assembles around each set of daughter chromosomes. This is the end of [ ], and the beginning of [ ].
- daughter chromosomes
- decondense
- nuclear envelope
- mitosis
- cytokinesis
What are the two distinct regulatory periods in mitosis?
G2M transition and metaphase to anaphase transition
G2/M transition is associated with an increase in [ ] activity.
M-Cdk
When does M-Cdk activity activates?
early in mitotic events: prophase, prometaphase, and metaphase
M-Cdk initiates [ ] associated with prophase. This prevents chromatids from becoming [ ].
- the chromosome condensation
- entangled during the stages that follow
Chromosome condensation is in part facilitated by the protein complex [ ].
condensin
Condensin also facilitates [ ]. This results in the chromatids becoming distinct, separable units.
sister chromatid resolution
What is the structure of condensin?
a five-subunit complex that resembles the four-subunit cohesin complex
How are condensin and the cohesin complex similar?
includes two coiled-coil subunits of the SMC family of proteins
During G2/M transition, M-Cdk initiates the [ ] in prometaphase.
breakdown of the nuclear envelope
M-Cdk phosphorylates proteins that lead to the [ ], and facilitate ites binding to sister chromatids.
formation of the mitotic spindle
In mitotic spindle, [ ] reach out away from the pole of which they originate. [ ] are oriented towards their respective role.
- plus-ends
- minus-ends
The plus ends of [ ] attach themselves to chromatids.
kinetochore microtubules
The kinetochore microtubules attach to chromatids via [ ] proteins at the [ ] of the chromatids.
- kinetochore
- centrosome
At each pole exists a complex called the [ ].
centrosome
The centrosome surrounds a pair of [ ].
centrioles
What are centrioles?
a cylindrical organelle composed primarily of tubulin. They are important for spindle organization and cytokinesis
Each kinetochore binds many [ ] which crosslink with each other, forming bundles known as [ ].
- microtubules
- K-fibers
Kinetochores are structured in a [ ] orientation. This decreases the likelihood that they will [ ].
- back-to-back
- attach to microtubules of the same spindle pole
How does the cell detect a correct attachment?
tension, associated with bi-orientation. When properly attached, kinetochores are pulled in [ ].
