Ap Bio: Unit 4- Cell Cycle

Cell division

fundamental process that allows organisms to reproduce, grow, and repair tissues. It involves the replication and distribution of a cell's genetic material (DNA) to produce two genetically identical daughter cells.

Genome

Organism’s entire genetic info

Chromatin

Complex of DNA and protein that serves as building blocks for chromasomes

6

The mitotic phase

The phase of the cell cycle that includes mitosis and cytokinesis.

The cell cycle

the ordered sequence of events where a cell grows, duplicates its DNA and organelles, and then divides into two genetically identical "daughter cells," a process vital for growth, repair, and reproduction in organisms, primarily divided into Interphase (growth & DNA prep) and the M Phase (Mitosis/division)

Mitosis length compared to other stages

Short

interphase

90% of the cell cycle, seperated into G1, S, and G2

Phases of mitosis

Prophase, Prometaphase, Metaphase, Anaphase, Telephase

Prophase

The first stage of mitosis, in which the chromatin condenses into discrete chromosomes visible with a light microscope, the mitotic spindle begins to form, and the nucleolus disappears but the nucleus remains intact.

Prometaphase

The second stage of mitosis, in which the nuclear envelope fragments and the spindle microtubules attach to the kinetochores of the chromosomes.

Metaphase

The third stage of mitosis, in which the spindle is complete and the chromosomes, attached to microtubules at their kinetochores, are all aligned at the metaphase plate.

Anaphase

The fourth stage of mitosis, in which the chromatids of each chromosome have separated and the daughter chromosomes are moving to the poles of the cell.

Telophase

The fifth and final stage of mitosis, in which daughter nuclei are forming and cytokinesis has typically begun.

G2 of interphase

G2 of interphase

can you see chromosomes in interphase

no

How much chromatid for one chromosome

2

prophase

Prophase

prometaphase

prometaphase

metaphase

metaphase

anaphase

anaphase

Telophase and Cytokinesis

Telophase

cytokinesis

Mitotic spindle

structure composed of microtubules which segregates chromosomes into the daughter cells during mitosis

Centrosome

primary microtubule-organizing center in animal cells. Regulates cell motility, adhesion and polarity in interphase, and facilitates the organization of the spindle poles during mitosis

microtubules

Maintain cell shape and provide rigidity, acting like internal tent poles. Forms the mitotic spindle, ensuring accurate separation of duplicated chromosomes into daughter cells.

prophase

prometaphase

metaphase

anaphase

telophase

Binary fission

A method of asexual reproduction in single-celled organisms in which the cell grows to roughly double its size and then divides into two cells. In prokaryotes, binary fission does not involve mitosis, but in single-celled eukaryotes that undergo binary fission, mitosis is part of the process.

The frequency of cell division varies in ____

type of cell

when do chromatids exist

Chromatids exist as a pair (sister chromatids) during the preparation and early stages of cell division (S phase, prophase, metaphase) and cease to be called chromatids once they separate and become individual chromosomes in anaphase

main phases of cell cycle

Interphase and Mitotic phase + (cytokinesis)

what all stages of interphase have in common

Cell grows through all the different phases of interphase

G1

Duplication of cell organelles, synthesis of proteins, RNA, and building blocks

Synthesis

Replication of genetic material and centrosomes

G2

synthesis proteins and RNA, makes organelles, reorganizes cellular contents

Interphase consists of how much of the cell cycle compared to the mitotic phase

a lot bigger

G0

Cell is outside the cell cycle, its just chilling

Prophase basically

cell prepare to divide. Chromatids condense, nuclear envelope no more

metaphase basically

Sister chromatids line up. microtubules attach to them

anaphase basically

microtubules pull apart chromatids

telophase basically

2 new nuclei

can a cell go through telophase without going through cytokinesis

yes, it would mean it has multiple nuclei

cytokinesis basically

cytoplasm splits

Animal cell cytokinesis

cleavage furrow is seen

Plant cell cytokinesis

vesicles are released to build cell plate to form new cell walls

G1 checkpoint

determines whether to complete the cell cycle. If no pass → go to G0

• growth factor

• adequate reserves (enough resources?)

• check for DNA damage

G2 check point

Is DNA replicated, are there major errors? If problems with DNA are detected, cell cycle is halted to repair DNA

When is the G1 checkpoint?

end of G1, before S

When is the G2 check point?

end of interphase

CDK

Cyclin-Dependent Kinases, they phosphorylate target proteins- activating or deactivating them. Concentrations present in relatively stable amounts, but inactive until bound to a cyclin

M Checkpoint when?

during metaphase, triggers exit from mitosis/cytokinesis to begin G1

M Checkpoint

make sure sister chromatids are attached to the spindle microtubules

Cyclins

regulatory proteins that bind to CDKs, activating them and determining when they act. Concentrations fluctuate throughout cell cycle

what is a kinase

type of enzyme that adds phosphate groups to other molecules, like proteins, sugars, or lipids

What is MPF

Maturation-Promoting Factor)/M-phase Promoting Factor

Cyclin-CDK complex that triggers a cell’s pass the G2 checkpoint into the M phase. It is needed to activate proteins that are used in mitosis (ex. microtubules)

What checkpoints are there in the cell cycle

G1, G2, M

the 2 regulatory proteins that are involved in cell cycle control

cyclins and cyclin-dependent kinases (CDK)

How does MPF stop?

when there enough cyclin is degraded so MPF can’t form anymore

when do cyclins start accumulating

G1 of interphase

when do cyclins start degrading

Mitosis, around prometaphase

When does cytokinesis happen

starts around anaphase to end of telophase

Internal signals

Molecules and events occurring inside the cell that monitor the cycle's progress. (ex. cyclins, dna damage)

external signals

Signals from the outside environment that influence cell division. (ex. growth factors, cell crowding)

Density dependent inhibition

a crucial cellular process where normal cells stop dividing once they become crowded, triggered by physical contact with neighboring cells, preventing overgrowth and maintaining tissue structure

Anchorage dependence

the biological requirement for most normal cells to attach to a surface or extracellular matrix (ECM) to grow, divide, and survive, preventing uncontrolled growth and ensuring cells only proliferate in appropriate locations within a tissue

Cancer and the body’s control mechanisms

Cancers may not need….to grow and divide

growth factors

Why do cancer cells may not need growth factors to grow/divide

• they may make their own growth factors

• may convey a growth factor’s signal without the presence of a growth factor

• may have a abnormal cell cycle control system

Cancer

uncontrolled cell growth resulting in a malignant tumor

transformation in cancer

when a normal cell becomes a cancerous cell

benign tumor

when abnormal cells remain at original site

malignant tumors

tumors that invade surrounding tissues, can metastasize

Hallmarks of cancer

• sustains proliferative signaling

• evade growth suppressors

• active invasion and metastasis

• enable replicative immortality

• induce angiogenesis

• resist cell death

oncogenes

mutated versions of normal genes (proto-oncogenes) that regulate cell growth, becoming permanently "on" and driving uncontrolled cell division, leading to cancer.

proto-oncogenes

normal genes essential for controlling cell growth, division, differentiation, and survival. They promote cell growth, regulate differentiation, and prevent apoptosis

telomerase genes

Reactivation of telomerase is a hallmark of most cancers, allowing them to grow uncontrollably. Provides instructions for the protein component of the telomerase enzyme, which adds DNA repeats (TTAGGG) to chromosome ends (telomeres) to prevent shortening and maintain cell division

p53 gene

a crucial tumor suppressor gene, often called the "guardian of the genome," that stops damaged cells from dividing and promotes DNA repair or programmed cell death (apoptosis) to prevent cancer

angiogenesis

the natural process of forming new blood vessels from existing ones, crucial for normal functions like wound healing, reproduction, and organ growth, but it also fuels disease, notably cancer, by supplying tumors with nutrients and oxygen, leading to rapid growth and metastasis

stability gene

the ability of an organism's or cell's genetic material (DNA) to remain consistent and unaltered across cell divisions, preventing mutations, rearrangements, and loss of genetic information

tumor suppressor gene

crucial genes that act as the "brakes" for cell growth, preventing uncontrolled cell division and tumor formation by repairing DNA, halting cell cycles, or triggering programmed cell death (apoptosis)

What would be the result of 2 mutated copies of a tumor suppressor gene in single-celled organism?

they reproduce uncontrollably

signal transduction pathway

series of steps that converts a signal on a cell’s surface into a specific cellular response

the most …. signal molecules bind to specific sites on ….. in the ….

water soluble, receptor proteins, plasma membrane

the 3 main types of membrane receptors

• G Protein-coupled receptors

• Receptor tyrosine kinases

• Ion channel receptors

Paracrine signaling

cells signal to cells nearby, no direct connection, signal molecules need to diffuse

Endocrine signaling

cells signal to cells far away

the 3 stages of cell signaling

1) reception

2) transduction

3) response

reception

signal molecule to receptor

transduction

relay molecules in a signal transduction pathway after initial signal

response

cellular activity after transduction