Week 1 Flashcards
(25 cards)
What happens during these phases: interphase
Preparation for division (most of the cell’s life)
Interphase has three main phases (plus G0):
What happens during:G0 (Gap 0)
Resting Phase
The cell is alive and functioning but not actively dividing. Some cells (like neurons) stay in G0 permanently. Others can re-enter the cycle when needed.
What happens during g1
Cell Growth. Cell grows in size. Makes proteins and organelles. Prepares for DNA replication. Checkpoint: Is the cell big enough? Is the environment okay?
What happens during S-phase
The entire genome is duplicated. Each chromosome becomes two sister chromatids. Centrioles (in animal cells) also duplicate.
What Happens during G2
Cell grows a bit more. Synthesizes proteins needed for mitosis. Checkpoint: Did DNA replicate correctly?
What happens during Cytokinesis
Cytokinesis is the process that physically separates the cytoplasm of one parent cell into two daughter cells, each with its own nucleus and organelles. It usually begins during telophase and finishes right after mitosis ends.
What is the role of centrosomes and microtubules during Mitosis
Centrosomes:Organize microtubules and form the mitotic spindle. Duplicate and move to opposite poles of the cell during prophase.
Microtubules:Form spindle fibers that move chromosomes.Kinetochore microtubules: Pull chromatids apart. Polar microtubules: Push cell poles apart. Astral microtubules: Anchor centrosomes to the membrane.
Differences between plants and animals cells that undergo cytokinesis differently
In animals:The cell membrane pinches inward, forming a cleavage furrow. A contractile ring made of actin and myosin helps pull the membrane tight. The cell eventually splits into two separate daughter cells.
In plants: A cell plate forms in the middle of the cell. Vesicles from the Golgi apparatus bring materials to build the new wall. The cell plate grows outward until it fuses with the existing cell wall, creating two separate cells.
When is checkpoint G1, G2, an S & what are they checking for
G1 Checkpoint (end of G1 phase)
Happens before the cell enters S phase.
Checks:
Is the cell big enough?
Is the environment favorable?
Is the DNA undamaged?
If it fails: the cell may enter G0 (resting phase).
S Phase Checkpoint (during S phase) Happens while DNA is being replicated.
Checks:
Is DNA being copied correctly?
Are there any replication errors or damage?
if errors are found, replication pauses for repair.
G2 Checkpoint (end of G2 phase) Happens before entering mitosis (M phase).
Checks:
Was all DNA copied correctly?
Is the DNA damage-free?
Is the cell ready to divide?
If problems are found, the cell waits or repairs the damage.
Know how cyclins and cyclin-dependent kinases help regulate the cell cycle
Cyclins and Cyclin-Dependent Kinases (CDKs):
Cyclins are proteins that rise and fall at specific times during the cell cycle. CDKs (Cyclin-Dependent Kinases) are enzymes that are always present, but only active when bound to a cyclin.
How They Work Together:
When a cyclin binds to a CDK, it forms a cyclin-CDK complex. This complex activates or inhibits other proteins to push the cell into the next phase (like from G1 to S, or G2 to M). Different cyclins are made for different phases (e.g., G1 cyclin, S cyclin, M cyclin).
Why They Matter:
They act like checkpoints—only letting the cell proceed if everything is ready. If cyclins/CDKs are faulty, the cell cycle can go out of control—this can lead to cancer.
What is meiosis?
Meiosis is a type of cell division that reduces the chromosome number by half, producing four haploid cells from one diploid cell.
How many phases are there in meiosis?
There are two main phases in meiosis: meiosis I and meiosis II.
True or False: Meiosis results in genetically identical cells.
False: Meiosis results in genetically diverse cells.
What is the purpose of meiosis?
The purpose of meiosis is to produce gametes (sperm and eggs) for sexual reproduction.
During which phase does crossing over occur?
Crossing over occurs during prophase I of meiosis.
Fill in the blank: Meiosis produces _____ cells.
haploid
What is the difference between mitosis and meiosis?
Mitosis results in two identical diploid cells, while meiosis results in four genetically diverse haploid cells.
Which phase of meiosis is responsible for separating homologous chromosomes?
Meiosis I is responsible for separating homologous chromosomes.
What are the two stages of meiosis II?
The two stages of meiosis II are prophase II and metaphase II.
True or False: Meiosis includes two rounds of cell division.
True: Meiosis includes two rounds of cell division.
What is the end result of meiosis II?
The end result of meiosis II is four haploid daughter cells.
Which process increases genetic variation during meiosis?
Crossing over and independent assortment increase genetic variation during meiosis.
Fill in the blank: The cells produced by meiosis are called _____ cells.
gamete
What occurs during anaphase I of meiosis?
During anaphase I, homologous chromosomes are pulled apart to opposite poles of the cell.
