10.1 Study Guide Flashcards
Why do multi-celled organisms divide? There are three main reasons.
- Growth and Development
- Repair and Renewal
- Reproduction
Why do single-celled organisms divide? There is one main reason.
Reproduction
What are totipotent embryonic stem cells?
Stem cells that can form all cell types of the body, including those that make up the embryo and the extra-embryonic tissues (like the placenta).
What are pluripotent embryonic stem cells?
Stem Cells derived from the inner cell mass of a pre-implantation embryo.
They can differentiate into any cell type in the body,
They can divide indefinitely in a lab setting while maintaining their ability to develop into various cell types.
What are multipotent embryonic stem cells?
Stem cell that can differentiate into multiple, but not all, cell types within a specific tissue or organ.
Why would cells in an organism need to divide to be replaced or renewed?
Cells can die from normal wear and tear or injury
Somatic stem cells divide to make more stem cells or specialized cells
Are all cell types renewed at the same rate?
No
Cell division in reproduction happens in two major ways. What are they? What is an example of each?
- asexual ; hydras
- sexual; mammals
What are the three things that can happen to a cell formed from mitotic division?
- Divide - the cell continues to grow in preparation for dividing again
- Differentiate - the cell specializes and matures and will never divide again
- Die
What is an example of a cell type that would grow and divide again?
Stem Cell
What is an example of a cell type that would differentiate?
Nerve Cell
Muscle Cell
What is apoptosis?
How does apoptosis help an organism?
Cell Death
This process eliminates unnecessary cells during development and removes unhealthy or damaged cells in the mature organism.
If a cell has unfixable DNA damage what are the two things that could happen?
- Apoptosis - cell death
- Cancer - uncontrolled cell division
What is the cell cycle?
The cell cycle is a series of events that a cell undergoes as it grows and divides.
What are the main phases of the cell cycle?
- Interphase
-G1 (Gap 1)
-S (Synthesis)
-G2 (Gap 2) - M phase
-mitosis
-cytokinesis - G0
What happens to a cell in Interphase?
This is the period between cell divisions where the cell grows, replicates its DNA, and prepares for division.
What three steps are included in Interphase?
- G1 (Gap 1)
- S (Synthesis)
- G2 (Gap 2)
What happens in the G1 (Gap 1) stage?
The cell grows, carries out its normal functions, and prepares for DNA replication.
What happens in the S (Synthesis) stage?
DNA replication occurs, creating two identical copies of each chromosome.
What happens in the G2 (Gap 2) stage?
The cell continues to grow and prepares for mitosis, ensuring DNA replication is complete and that the cell is ready to divide.
What happens to a cell in M Phase?
The cell divides into two daughter cells.
What two steps are included in the M Phase?
Mitosis and Cytokinesis
What happens in the Mitosis stage?
Division of the cell into two daughter cells each with the same number of chromosomes.
What happens in the Cytokinesis stage?
Division of the cells cytoplasm and formation of two separate cells.
What is the G0 phase of the cell cycle?
A resting phase where cells are not actively dividing.
What are two reasons a cell would enter the G0 phase?
- There are not enough resources to divide
- To differentiate
Why does the Cell Cycle have checkpoints?
Cell cycle checkpoints act as surveillance mechanisms, monitoring the order, integrity, and correctness of major events in the cell cycle.
Defects in cell cycle checkpoints can lead to genetic instability and uncontrolled cell division, contributing to the development of cancer.
What are the four key checkpoints in the cell cycle?
G1
S
G2
M
What happens at the G1 checkpoint?
Ensures cell size, DNA has no damage, and adequate growth factors are present before the cell enters S phase
What order do these events occur in as a cell enters G1?
A. DNA copies are divided and moved to opposite ends of the cell and the cell divides in two
B. Cell continues to grow and replicate other organelles/ parts needed to divide
C. Cell grows and prepares to replicate DNA
D. DNA is replicated
C
D
B
A
What happens at the S checkpoint?
Verifies that no errors occurred during DNA replication
What happens at the G2 checkpoint?
Ensures DNA has no damage, the chromosome set is complete and there are enough cell components
What happens at the M checkpoint?
Verifies that all chromosomes are correctly attached to spindle fibers before allowing cell division to proceed.
All sister chromatids are attached to the mitotic spindle.
What are cell cycle checkpoints controlled by?
Inhibitory and Stimulating Proteins, including cyclin-dependent kinases (Cdks) and cyclins
What happens to a cell if it fails a checkpoint?
It can be stopped at that point, allowing time for repair or, if damage is irreparable, programmed cell death (apoptosis) will occur.
Which phase does the cell replicate its DNA ensuring each daughter cell has a complete set of chromosomes?
S phase
The cell grows and accumulates the necessary resources for division during which phase?
Interphase
What has to be passed on to daughter cells during cell division?
- DNA - exact copy of genetic material
- Organelles, Cytoplasm, Cell Membrane, Transcription Factors, Enzymes
What are growth factors and what do they do?
Often a protein or peptide.
Are released by body cells and bind to specific cell surface receptors to stimulate other nearby cells to divide (or differentiate - depending on the type of growth factor).
What is density-dependent inhibition?
When cell division and growth are stopped or slowed down when cells reach a certain density, often due to cell-to-cell contact (receptors on adjacent cells bind and send inhibition signals) or limited resources.
What happens if some cells are removed in a density-dependent inhibition scenario?
The gaps where the cells were removed are filled back in and then cell division stops again.
What is anchorage-dependent inhibition?
When cells require attachment to a surface (extracellular matrix) to survive and divide, and their growth is inhibited if they are not anchored.
What does the root “kine” mean?
Movement
To set things in Motion
What do “kinases” do?
Add phosphate groups to target enzymes
Activating or inhibiting the enzyme by changing its structure with the phosphate group.
Turn on/ off various cellular processes
What are cyclins and what is their role in the cell cycle?
Regulatory proteins that control the progression of cells through the cell cycle by binding to and activating cyclin-dependent kinases (CDKs), which then phosphorylate target proteins to drive the cell through different phases.
Cyclin levels fluctuate throughout the cell cycle, with different cyclins being produced and degraded at different stages.
What are Cyclin-Dependent Kinases (CDKs)? What do they do?
Enzymes that regulate the cell cycle by phosphorylating (adding phosphate groups to) specific proteins, which in turn activates or inactivates them, driving the cell cycle forward.
Are CDKs active on their own?
No - CDKs are inactive on their own and require binding to proteins called cyclins (forming CDK-Cyclin Complexes) to become active.
Why are CDK-Cyclin complexes important for the G1 to S transition in the cell cycle?
During the G1/S transition, the Rb protein, which normally inhibits cell cycle progression, is phosphorylated by a CDK-Cyclin complex leading to its inactivation.
The inactivation of Rb releases E2F transcription factors, which then activate genes involved in DNA replication and cell cycle progression, driving the cell into the S phase.
What does MFP stand for?
What is MFP?
What does MFP do?
Maturation-promoting factor
(AKA) mitosis-promoting factor or M-phase-promoting
factor
A cyclin-(cyclin dependent kinase or Cdk) complex
Triggers the cell cycle transition from G2 to M phase (mitosis) by phosphorylating proteins needed during mitosis
List 1 - 4 the correct order of events for cell cycle regulation.
- Cyclin/ cdk complexes form to activate cdk
- Growth Factors are released
- CDK phosphorylates target enzymes and triggers the next phase of the cell cycle
- Cyclin levels increase
2
4
1
3
Cancer is a failure of _______?
cell division control
How many chromosomes do human cells contain?
46
Common treatments for cancer?
Surgery - remove problem cells
Chemotherapy - disrupts cell division
Radiation - disrupts cell division
What is a Proto-Oncogene?
Normal cellular genes that regulate cell growth and differentiation, and when mutated or overexpressed, they can become oncogenes, which drive uncontrolled cell growth and potentially lead to cancer.
Think of proto-oncogenes as the “gas pedal” of cell growth, and oncogenes as a “stuck-down” gas pedal, causing uncontrolled acceleration.
What is a Tumor Suppressor Gene?
Normal genes that act as “brakes” on cell division, ensuring cells don’t grow out of control or become cancerous.
They regulate cell growth, promote apoptosis (programmed cell death), and repair DNA damage.
When tumor suppressor genes are mutated or inactivated, cells can grow and divide uncontrollably, potentially leading to cancer.
What is p53 and example of?
Tumor Suppressor Gene
Oncogenes and Suppressor Genes can cause cancer. Which is dominant and which is recessive?
Oncogenes - dominant - only one mutated gene is needed to drive the cycle to accelerate
Suppressor Genes - recessive - other suppressor genes can slow the cell cycle down when one is mutated.
Measurements of DNA per nucleus were taken on a large number of cells from a growing fungus. The DNA levels ranged from 3 to 6 picograms per nucleus. During which stage of the cell cycle would the DNA consistently have 6 picograms of DNA?
G0, G1, S, G2 or M
The DNA would consistently have 6 picograms per nucleus during the G2 phase of the cell cycle, as this is when the DNA is fully duplicated after replication in the S phase.
Why does cell division remain important to an adult organism even after it is fully developed?
After growth, division remains important in normal cell turnover, such as in our skin and gut, where cells are continuously renewed. Other cells have to divide to heal wounds like skin cuts or broken bones.
Cells divide, differentiate, or die. What is differentiation?
When cells stop dividing to specialize in structure and function. Once differentiated, some cells may divide again under certain conditions.
