Exam 1 Flashcards
Cell division requires 3 things:
- Replication of genetic material
- Accurate segregation of genetic material
- Division of cytoplasm (liquid in cells) between 2 cells
Prokaryotes
- Small cell size
- No nucleus
- No membrane-bound organelles
- DNA in circular chromosomes
- Cell division by binary fission
Eukaryotes
- Large cell size
- Nucleus present
- Has membrane-bound organelles
- DNA in linear chromosomes (except for mitochondrial and chloroplast DNA)
- Cell division by mitosis/meiosis
Binary fission
nucleoid
- Requires duplication and segregation of genetic material and division of cytoplasm
- Genetic material is in the nucleoid: a non-membrane bound region of compacted DNA (contains proteins)
1. Cell increases in size
1. The circular bacterial chromosome is replicated
1. Replication begins at the origin of replication and proceeds in both directions to the site of termination
1. The 2 chromosomes are separated and segregated to opposite ends of the cell
Prokaryotes
First level of DNA compaction:
DNA is looped around SMC proteins to form loop domains
2nd level of DNA compaction
DNA loops are further compacted into supercoils
Septation
dividing cell into 2
FtSZ proteins
- FtsZ proteins form a ring around the middle of the cell called a Z-ring
- Z-ring begins to shrink and divide the cell
- The septum forms as the Z-ring shrinks and continues until the cell is divided into 2 daughter cells
Cohesin proteins
hold sister chromatids together after DNA replication
bind to the inner services of centromeres and each other
Kinetochore proteins
site of microtubule attachment during cell division (outer part of the centromeres)
telomeres
- repetitive sequences of DNA that protect and stabilize the ends of chromosomes
- Each time a cell divides, the telomeres become shorter
- Once they become too short, the cell can’t divide
- Telomere length can be maintained by the enzyme complex telomerase
- Most cells in body stop making telomerase after embryonic development
- In 90% of human cancer cells, telomerase production has been reactivated
cyclins
regulatory proteins that accumulate then dissipate in the cell in a cell-cycle-specific patterns
Kinases
protein enzymes that phosphorylate (add a phosphate group to) other molecules
phosphatases
enzymes that dephosphorylate (remove a phosphate group from) other molecules
G1/S (start or restriction) checkpoint
- Sufficient nutritional size and state
- No DNA damage
G2/M checkpoint
- commitment to proceed into mitosis or meiosis (regulated by cyclin/CDKs’s)
- DNA completely replicated
- No DNA damage
- Sufficient cell size
Spindle checkpoint
- commitment to proceed into anaphase (segreagte the replicated DNA) regulated by APC (anaphase promoting complex)
- Chromosomes aligned properly
- Chromosomes attached to microtubules
Three Phases of DNA Replications
Initiation: accumulation of all the enzymes necessary to replicate DNA
Elongation: process of replicating the DNA
Termination: ending elongation
End replication problem
Why can’t DNA pol 3 can’t add the 1st nucleotide
t needs a 3’ OH
Primase
Primase (an RNA polymerase) begins the DNA replication process and adds several RNA nucleotides ‘primer sequence’
DNA polymerase 1
removes and replaces RNA nucleotides w/ DNA nucleotides
