Cell Cycle and Regulation Quiz

review notes, virtual lab, mitosis lab

how are chromosomes formed?

DNA wraps around histones that coil into nucleosomes, which coil to form chromatin fibers that supercoil into chromosomes

chromatid

single “stick”, one of two in a chromosome

sister chromatids

two identical chromatids put together

centromere

central region of the chromosome that joins sister chromatids together

homologous chromsomes

same chromosome structure and gene loci, variation in alleles, one from dad and one from mom

p arm

shorter arm

q arm

longer arm

telomere

ends of chromosomes; maintains stability and prevents degradation of the chromosome

kinetochore

protein complex attached to the centromere; connects to spindle fibers to help in cell division

spindle fibers

microtubules that pull sister chromatids apart in cell division

centrioles

part of the cytoskeleton that makes spindle fibers

aster

guides centrioles around to line them up

haploid cell

single set of chromosomes; n amount of chromosomes

diploid cell

two sets of chromosomes; 2n amount of chromosomes

what are the 2 main phases of the cell cycle

interphase and M (mitosis) phase

phases of interphase

G₁, S, G₂

G₁ (gap) phase

cell grows and makes copies of proteins/organelles

S (synthesis) phase

DNA replication occurs, forming sister chromatids

G₂ (gap) phase

cell grows more and makes more copies of proteins/organelles

M (mitotic) phase

produces genetically identical daughter cells that are diploid, occurs in somatic cells

what processes occur during M phase?

mitosis (eukaryotic only), cytokinesis

phases of mitosis

prophase, prometaphase, metaphase, anaphase, telophase (PMAT)

prophase

chromatin fiber condenses into visible chromosomes, centrioles move to opposite ends of the cell, spindle fibers begin to form, nucleolus breaks down

prometaphase

nuclear envelope breaks down, kinetochores form, spindle fibers attach to kinetochores

metaphase

chromosomes align in the metaphase plate, spindle fibers attached to kinetochores initiate movement

anaphase

sister chromatids pulled apart to opposite poles of the cell by spindle fibers

telophase

daughter nuclei form around each set of separated chromatids, chromosomes begin to decondense back to chromatin fibers, spindle fibers disperse

cytokinesis

cytoplasm continues to divide to form 2 distinct daughter cells

cytokinesis in animal vs. plant cells

in animal cells, a cleavage furrow forms, and in plant cells, a cell plate forms

when are the centrosomes duplicated, and what would happen to a cell that failed to duplicate this structure?

S phase; cell would improperly divide into aneuploids

How do prokaryotic cells divide in comparison to eukaryotic cells?

prokaryotes undergo binary fission while eukaryotic cells undergo mitosis/meosis

cell cycle checkpoints

serve as control points to assess the cell, G₁, G₂, M

G₁ checkpoint

occurs during G₁ phase, checks for size, nutrients, gorwth factors, and DNA damage

what happens if the cell passes the G₁ checkpoint

moves into S phase

what happens if the cell fails the G₁ checkpoint

goes into G₀ (resting phase) or undergoes apoptosis

G₀ phase

state where the cell is nondividing, may enter this to repair any injury or damage/insufficient nutrients to move into replication, neurons are permanently in the G₀ phase

G₂ checkpoint

occurs at the end of the G₂ phase, checks DNA replication before the cell can move into mitosis

what happens if a cell passes the G₂ checkpoint?

enters M phase

what happens if a cell fails the G₂ checkpoint?

fixes errors or undergoes apoptosis

M checkpoint

occurs near the end of metaphase, checks that all chromosomes are properly attached to the spindle fibers and aligned

what happens if the cell passes the M checkpoint?

cell divides

what happens if the cell fails the M checkpoint?

apoptosis

internal cell cycle regulators

molecules inside the cell that control the progression of the cell cycle

cyclins

proteins whose levels fluctuate throughout the cell cycle

CDKs

cyclin-dependent kinases, enzymes that activate when bound to cyclins and phosphorylate other proteins, always present in the cell

what happens after a CDK activates/inactivates another protein?

cyclin degrades and CDK returns to its inactive state

external cell cycle regulators

molecules from outside the cell that influence division

growth factors

proteins released from other cells that stimulate cell division

density-dependent inhibition (aka contact inhibition)

cells stop dividing when they contact other cells; prevents overgrowth

anchorage dependence

to divide, cells must attach to something, ensuring they only grow in appropriate locations

cancer cells

cells that uncontrollably divide due to failures in cell cycle regulation

how do cancer cells develop

mutations in genes that regulate the cell cycle

tumor

areas of massive cell buildup and growth

benign tumor

stays in the same place, non-cancerous, usually harmless

malignant

cancerous growth that spreads to other parts of the body, harmful

proto-oncogene

when activated, they signal for cell division to start, gas pedal

oncogene

mutated form of proto-oncogene, gene always activated, so cell divides constantly, DOMINANT trait (only 1 mutated allelle neccessary), foot stuck on the gas pedal

tumor supressor genes

slows cell division, repairs mistakes, or causes apoptosis, brake pedal

examples of tumor suppressor genes

p53 and Rb

example of proto-oncogene

RAS

mutated tumor suppressor gene

cell doesn’t stop division even if mistakes are found, RECESSIVE trait (2 mutated alleles), taking your foot off of the brake pedal