The Cell Cycle Flashcards
Prokaryotes can make ______ of their genomes then segregate one cpoy into each of the 2 daughter cells. This is a form of _________ ___________ called binary fission
exact copies, asexual reproduction
What are the 2 eukaryotic cell stages?
Interphase (S, G1, G2)
Mitosis
What processes does interphase involve?
-Preparations for cell division
-DNA replication in S phase
-Increase in cell size
-G1 prepares for DNA synthesis
-G2 prepares for mitosis
What is the Go phase?
A long, short, or permanent pause in cell division after mitosis
What is the G1 phase?
Gap growth phase, prepares fro DNA synthesis
What is the S phase?
DNA replication in the nucleus
What is the G2 phase?
Gap growth phase, prepares for mitosis
How do homologous chromosomes form?
Homologous chromosomes replicate (centromeres included), homologs fuse at the centromere and become sister chromatids in a homologous chromosome
When do chromosomes become compacted?
Between G2 and M phase
What happens in prophase?
-Identical sister chromatids join at centromeres
-Centrosomes begin to radiate microtubules forming a mitotic spindle
What happens in prometaphase?
-Nuclear envelope breaks down
-Microtubules attach to kinetichores on the centromeres
-Polar microtubules from the centrosomes push the poles apart
What happens in metaphase?
-Alignment of chromosomes at the metaphase plate
-Kinetichore microtubules attach to kinetichores and facilitate alignment
What happens in anaphase?
-Kinetichore microtubules shorten
-Sister chromatids separate and move towards spindle poles
-Polar microtubuules elongate the cell
What happens in telophase?
-2 daughter nuclei form
-Chromosomes decondense
-cytokinesis signals end of mitosis
How does cytokinesis happen in animal cells?
-A contractile ring made of motor proteins contract bundles of actin fibers along the middle of the cell
-Cleavage furrow separates the cell in 2
The MPF depends on ______ and _____ to regulate the cell cycle
cyclin, cyclin dependent kinase
Cyclin was discovered due to ______________, increasing and decreasing with each division
oscillation in intensity
What are the 3 types of CDK?
-G1/S cyclin CDK; prepares for DNA replicaiton
-S cyclin CDK; initiates DNA synthesis
-M cyclin CDK; initiates mitosis
What are cell cycle checkpoints?
They block cyclin-CDK activity if something goes wrong and can pause cell division
What are the 3 cell cycle checkpoints?
-DNA damage checkpoints
-DNA replication checkpoints
-Spindle assembly checkpoint
DNA damage checkpoints
End of G1, only undamaged DNA enters S phase
DNA replication checkpoint
End of G2, mitosis only begins when all DNA is replicated
Spindle assembly checkpoint
Mitosis is only complete if all chromosomes are attached to a kinetichore microtubule
How does the DNA damage checkpoint work?
-Protein kinases phosphorylate P53 to inhibit cell cycle
-P53 is usually present in low levels; when phosphorylated it accumulates
-CDK pauses G1
How does the spindle assembly checkpoint work?
-In prometaphase regulatory proteins monitor whether sister chromatids are attached to microtubules
-Unattached kinetichores create a wait signal and checkpoint proteins are recruited
-A lack of tension in the centromere activates these proteins
-When each chromatid is attached separase enzymes break chromatid attachments
Name of researchers who proved semiconservative model
Mehelson and stahl
How was DNA proved to be semiconservative?
Using nitrogen isotopes, when centrifuged DNA sat between light and heavy isotopes, proving a combination
Prrokaryotes have ___ origin/s of replicatiotn
1
The template strand is read _______ and written _____
3’ to 5’
5’ to 3’ (DNA polymerase builds 5’ to 3’)
What are replication forks
Where DNA unwinding begins
What is RNA primer?
Needed to begin replication initiation, 5-10 nucleotides in length
What direction does DNA polymerase build?
5’ to 3’
