Cell Reproduction
One difference between asexual and sexual reproduction
What is, asexual reproduction produces genetically identical offspring from one parent; sexual reproduction combines genes from two parents?
Give one reason cells can't survive if they become too large.
Example: The DNA would be overloaded and the cell could not exchange materials efficiently across the membrane.
Which phase of mitosis shows chromosomes lined up at the cell center: prophase, metaphase, anaphase, or telophase?
Metaphase
Name one external and one internal control of the cell cycle.
External: growth factors or signals from other cells. Internal: cyclins and Cdks.
What is a carcinogen? Give one example
A carcinogen is an agent that can cause mutations leading to cancer. Example: chemicals in tobacco smoke.
One advantage of sexual reproduction compared to asexual reproduction
Example: Sexual reproduction increases genetic variation, which can help populations adapt to changing environments
Explain why a large surface area to volume ratio is important for cells.
A larger surface area relative to volume allows efficient diffusion of nutrients and wastes across the membrane to meet interior needs
List the three parts of interphase and one major event in each.
G1: growth and organelle duplication; S: DNA (chromosome) replication; G2: growth and checking duplicated chromosomes.
What are cyclins and why are they important for the cell cycle?
Cyclins are regulatory proteins that rise and fall in concentration to activate Cdks and drive the cell past checkpoints.
When is a tumor classified as malignant?
When it spreads from its original location to other parts of the body (metastasizes).
Describe binary fission and state in which type of cells it occurs
Binary fission: circular DNA is copied, cell elongates, and the membrane pinches inward to split the cell; occurs in prokaryotes (bacteria).
If a cell's volume increases faster than its surface area, what problem occurs for exchange of materials? Explain briefly.
The cell cannot take in enough nutrients or remove wastes fast enough; diffusion distances become too great and concentration gradients fail.
List the phases of mitosis in order.
Prophase → Metaphase → Anaphase → Telophase.
Describe how cyclins and Cdks create checkpoints in the cell cycle.
Cyclins bind Cdks at specific times to form active complexes that phosphorylate target proteins, allowing progression; when cyclins degrade, the checkpoint halts progression.
List three common treatments for cancer.
Radiation therapy, chemotherapy, surgery.
Explain why chromosomes form from chromatin before mitosis.
Chromatin condenses into chromosomes to organize and compact DNA so it can be separated without tangling
Compare how surface area and volume scale as a cell grows (qualitative explanation).
Surface area scales with the square of linear dimensions, volume scales with the cube; volume grows faster than surface area as size increases
Explain why interphase is much longer than mitosis and give the approximate fraction of the cell cycle it occupies
Interphase includes growth, DNA replication, and checkpoints — processes that take time; it is about 90% of the cell cycle.
Give an example of how a signal from another cell (external cue) could affect the cell cycle (short scenario)
Example: A neighboring cell releases growth factors after injury, signaling nearby cells to divide to repair tissue.
What is a stem cell and where would you find totipotent stem cells?
A stem cell is an unspecialized cell that can divide indefinitely and become different cell types. Totipotent stem cells are found in early embryos.
Describe two cellular events that must occur so each daughter cell gets a full set of genes after cell division.
Chromosomes duplicate (S phase) so each sister chromatid can be pulled to opposite poles during mitosis; centromeres and spindle fibers help ensure proper segregation.
Describe two ways a cell can manage increases in size (list and briefly explain).
Cells can divide to remain small; cells can become flattened or develop membrane folds to increase surface area relative to volume.
Explain why chromosomes must be duplicated before mitosis and how that ensures each daughter cell receives the right genetic information.
DNA replication produces identical sister chromatids so that when mitosis separates them, each daughter cell gets a full set of chromosomes.
Explain how a mutation in cyclin production could allow abnormal cells to bypass checkpoints (brief molecular/functional explanation).
If cyclins are overproduced or mutated, Cdks may be continually active, allowing the cell to pass checkpoints without proper checks (e.g., damaged DNA), enabling uncontrolled division.
Describe one medical use of stem cells (regeneration or repair) and outline a basic benefit and an ethical consideration.
Example: Using stem cells to regenerate damaged heart tissue after a heart attack — benefit: can replace lost cells and restore function; ethical consideration: source of stem cells (embryonic stem cells raise ethical concerns), so consent and alternatives should be considered.