Chapter 12 (Mitosis) Flashcards
Which type of cell division is responsible for asexual reproduction, growth, development and repair?
Mitosis
What type of cells do mitosis produce?
identical somatic cells (body cells)
Asexual reproduction (3)
- One parent2. Offsprings are identical3. No gametes
What are the 3 key events of mitosis?
- DNA replication➡️ 2 sister chromatids Per chromosoem➡️ Sister chromatids: 2 identical dna molecules attached by centromere2. Mitosis ➡️ chromosomes divided3. Cytokinesis
What are the 4 phases of the cell cycle and what happens in each one?
G0: quiescence➡️ “cell pause”G1: Gap phase 1➡️ Cell grows, checkpointS: synthesis➡️ DNA replication (chromosomes gains 2 sister chromatids) by DNA polymerase)➡️ duplication centrosomes/MTOC (poles of mitotic spindle)G2: Gap phase 2➡️ preparation for mitotic phase
What is the G1 checkpoint?
✅ monitors cell size✅ environmental conditions✅ if ready to divide
In the S phase how many chromosomes and chromatids do humans have?
46 chromosomes but 92 chromatids
Which phases make the interphase?
G1, S and G2
During interphase are individual chromosomes visible?
NO
What are the sub-phases of Mitosis?
P ➡️. ProphaseP ➡️ PrometaphaseM ➡️ MetaphaseA ➡️. AnaphaseT ➡️. Telophase (cytokinesis)
Prophase/prometaphase:
➡️ chromosomes condense into X shape➡️ Nucleolus dissapears➡️ Nuclear envelope disappears➡️ Centrosome are at opposite poles➡️ Mitotic spindle captures chromsomes
Metaphase: (3)
“M” ➡️. Middle➡️ Chromosomes align at the metaphase plate➡️ Kinetochore MT attach at the chromosomes centromere➡️ polar MT overlap [Image]
Anaphase:
”A” ➡️ Away➡️ Sister chromatids are pulled apart from each other to opposite poles by the reducing of polar Mt overlap (elongates spindle) and the kinetochore that becomes shorter pulls the sisters apart
Telophase:
”T” ➡️ Two✅ Nuclear envelope reforms ➡️. 2 nuclei appear ➡️ Nucleolus reappears✅ Chromosomes decondenses ➡️ spindle disappears
At which phase does cytokinesis occur?
Telophase!
Cytokinesis from animals and plants:
ANIMAL: cleavage furrow forms ➡️ Pinching CM by actomyosin ring (microfilaments)PLANT: cell plate froms [Image]
What is cell division called in bacteria?
binary fission
what are the 5steps of binary fission?
- Single circular chromosome is replicated at the origin of replication2. Cell elongates and two copies move to opposite ends3. Cell membrane grows inward4. Cell wall forms5. Cell splits [Image]
What are the 3 checkpoints that monitor the cell cycle?
1️⃣ G1 Checkpoint → Checks if the cell is big enough & has nutrients.2️⃣ G2 Checkpoint → Checks if DNA was copied correctly.3️⃣ M Checkpoint → Ensures chromosomes are attached to spindle fibers before division.
What happens at the G1 checkpoint, what stops division of cells (4)?
G1 stops the cell division if:➡️ cell too small, lacks nutrients➡️ isn’t attached to a surface (anchorage dependence)➡️ once the surface is covered with cells➡️ dna damage
What happens when DNA damage is beyond repair?
cells undergo apoptosis
What is apoptosis?
programmed cell death
Steps of Apoptosis:
1️⃣DNA fragmentation- chromatin condenses and nucleus fragmentsEnzyme: nucleases2️⃣ Formation of apoptotic bodies (blebs)- cellular fragmentationEnzyme: proteases3️⃣ Phagocytosis of apoptotic bodiesMacrophages: White blood cells [Image]
Does the cell lyse (burst) during apoptosis?
No!
Nucelase:
Break down nucleic acid (DNA)
Protease
Enzyme that breaks down proteins
What does the mitochondria activate after being triggered by a signal (apoptosis)
CASPASES✅ Caspases = Enzymes that control apoptosis✅ They act as proteases & nucleases‼️WITHOUT CASPASES APOPTOSIS WOULDN’T HAPPEN
What is the main difference between necrosis and apoptosis?
Necrosis is an accidental cell death ➡️ tissue damageApoptosis is a programmed cell death ➡️signals
What happens in necrosis?
Cell lysis (bursts) ➡️ Plasma membrane breaks ➡️ Organelles spills out [Image]
What does necrosis trigger?
inflammation
What happens in apoptosis?
DNA condenses and fragments ➡️ Cells break into apoptotic bodies ➡️ macrophages eats the bodies (phagocytosis)
Does apoptosis trigger inflammation?
NO
What are the internal (2) and external triggers (2) for apoptosis?
INTERNAL:1. DNA damage2. Protein misfolding in EREXTERNAL:1. Death signals from nearby cells2. Immune cells detect infected cells
What happens if G1 checkpoint fails to work?
uncontrolled growth and division of cells ➡️ Creation of cancer cells
True or False: Binary fission creates 2 identical daughter cells
t
Is G2 before or after S phase?
AFTER!
Which cell cycle phase has the least amount of DNA?
✅ G0 phase (or G1 phase)➡️ The cell has not duplicated its DNA yet.
