exam 3 flashcards

Binary Fission

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

1. Origin replicates (single origin of replication)

2. Both origins of replication move to opposite ends of cell

3. 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.

Prokaryotes

Simple, unicellular organisms that do not have a nucleus or membrane-bound organelles; reproduce mainly by binary fission.

Eukaryotes

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?

The series of phases that a cell goes through in order to divide and produce daughter cells, consisting of interphase, mitosis, and cytokinesis.

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

Interphase

The phase where the cell spends most of its time, preparing for division by growing and replicating its DNA.

Mitosis

The process of cell division in eukaryotic cells where the nucleus divides, resulting in two identical daughter cells.

Cytokinesis

The final stage of cell division where the cytoplasm divides, resulting in two separate cells.

Cell Senescence

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)

Telomeres

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.

Telomerase

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”

Cyclins

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

Cyclin-dependent Kinases (CDKs)

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

Maturation Promoting Factor (MPF)

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

G1 Checkpoint

A checkpoint that monitors whether the environment is favorable for cell division (growth factors).

• It also checks for DNA damage.

G2 Checkpoint

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

M Checkpoint

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?

1. Cyclin B synthesized in S and G2.

2. Cyclin B binds CDK1 making MPF

3. MPF phosphorylates proteins during M phase

4. 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.

Density-dependent Inhibition

The phenomenon where crowded cells stop dividing due to lack of space or resources.

Anchorage Dependence

The requirement for cells to be attached to a solid surface in order to divide.

Neoplasm

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

Malignant

When cells invade adjacent tissue they are considered cancer

Malignant = cancer

Benign

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)

Cell Division

The process by which a parent cell splits into two or more daughter cells.

Microtubules

Cytoskeletal structures that pull chromosomes apart during mitosis.

Chromosome

A structure of nucleic acids and proteins that carries genetic information.

Cyclin B

A specific cyclin involved in the regulation of the cell cycle, particularly related to the transition from G2 to M phase.

Cdc2 (cdk1)

A cyclin-dependent kinase that, when activated by cyclin B, plays a key role in promoting the transition from G2 to M phase.

Anaphase

The stage in mitosis where sister chromatids are separated and pulled to opposite poles of the cell.

Cellular Aging

The gradual decline in cell function due to cellular senescence and telomere shortening.

Telomere Shortening

The progressive loss of nucleotide sequences at the ends of chromosomes with each cell division, linked to aging.

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.