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A method of asexual reproduction occurring in prokaryotes where a single organism replicates its DNA and divides into two identical cells.
doesn’t use mitosis
takes place in the cytoplasm → doesn’t have a nucleus
Origin replicates (single origin of replication)
Both origins of replication move to opposite ends of cell
Cell elongates and then divides
Mitosis
A process of cell division in eukaryotic cells that results in two identical daughter cells, involving multiple phases such as prophase, metaphase, anaphase, and telophase.
Simple, unicellular organisms that do not have a nucleus or membrane-bound organelles; reproduce mainly by binary fission.
Complex organisms whose cells contain a nucleus and membrane-bound organelles; typically reproduce through mitosis.
What is happening here?
A = Binary vision = no nucleus
B = Microtubules go through the nucleus and pulls chromosomes apart
C = Micro form within the nucleus and pull apart
D = Mitosis
What is the Cell Cycle and what are the phases?
What happens during S Phase?
During S Phase; every time you replicate you’re losing a small amount of DNA specifically in the daughter cells
DNA replication occurs, resulting in the duplication of the chromosomes in preparation for cell division.
Part of interphase
The phase where the cell spends most of its time, preparing for division by growing and replicating its DNA.
The process where cells can not keep dividing and growing because of the shortening of telomeres.
Cell can no longer divide because you’re losing proteins and DNA needed for cell maintenance
Losing DNA at the end of a strand = shortening telomeres (in picture)
The repetitive nucleotide sequences at the ends of chromosomes that protect them from deterioration during cell division.
ends of chromosomes have tandem repeats (such as GGGGTT). Telomeres shorten each time the cell divides
Loss of telomeres and shortening of chromosomes is thought to be an important reason why cells age and undergo senescence
Who is Henrietta Lacks?
an African American woman whose cancer cells were taken without her knowledge in 1951.
Her cells became the first immortal cell line, known as HeLa cells (immortal HeLa Cell line), which have been crucial for medical research.
An enzyme that extends/ restores telomeres, allowing certain cells (like germ, stem, and cancer cells) to divide indefinitely.
The telomerase gene has been cloned. Introduction into human fibroblasts prevents senescence and makes cells immortal.
“the key to immortality”
A family of proteins that regulate the cell cycle by activating cyclin-dependent kinases (CDKs) through their abundance during different phases.
Cyclin B accumulates during interphase but drops quickly in mitosis. Cyclins control the cell cycle in all eukaryotic cells
Proteins that phosphorylate and cause cells to move to next cell cycle phase. They are always present but they require a cyclin to become an active kinase
A regulatory protein complex composed of cyclin and CDK that promotes the transition from G2 phase to M phase in the cell cycle.
first purified complex of cyclin and cdk, promotes maturation of oocytes by completion of meiosis
Why is Cyclin B and Cdc2 important?
Cyclin B is the regulatory subunit and must be present for function of the Cdc2 (cdk1) kinase
Cdc2 (cdk1) phosphorylates nuclear lamins (breaks down nucleus) and proteins that condense chromosomes
What are checkpoints in the cell cycle?
They prevent the cell from entering the next phase of the cycle before the preceding phase has been completed
A checkpoint that monitors whether the environment is favorable for cell division (growth factors).
It also checks for DNA damage.
A checkpoint that checks if DNA replication is complete.
Also causes cell cycle arrest in response to DNA damage, allowing cells to repair any damaged DNA before division
A checkpoint that monitors whether chromosomes are intact and lined up properly before the cell proceeds with division.
What is MPF role in the cell cycle?
Cyclin B synthesized in S and G2.
Cyclin B binds CDK1 making MPF
MPF phosphorylates proteins during M phase
Cyclin B is degraded in anaphase.
Growth Factors
A property of normal cells
Normal cells within the body respond to growth factors (example: hormones or cytokines) to function within the cell cycle.
A new abnormal growth of cells / tissue that arises from uncontrolled cell division.
can also be a tumor
(neo = new, plasm = growth)
Cancer is a ….
Cancer is a malignant neoplasm (or tumor)
Cancer cells leave normal cell cycle
When cells invade adjacent tissue they are considered cancer
Malignant = cancer
Describes non-cancerous tumors that do not invade surrounding tissues.
but, can kill if it’s not possible to remove tumor due to location (brain)
Why study cancer?
Cancer is a disease of cells.
Studying cancer cells contributes to our understanding of normal cell biology and the mechanisms of growth and division.
Often using immortal cell lines like HeLa.
