cell cycle Flashcards
What happens during prophase in mitosis?
Chromosomes condense and become visible, the nuclear envelope breaks down, and spindle fibers form.
What is the role of spindle fibers during prometaphase in mitosis?
Spindle fibers attach to the kinetochores on the centromeres of chromosomes.
What happens during metaphase in mitosis?
Chromosomes align at the metaphase plate and spindle fibers attach to both sister chromatids of each chromosome.
What is the result of anaphase in mitosis?
Sister chromatids separate and are pulled towards opposite poles of the cell by spindle fibers.
What happens during telophase in mitosis?
Chromosomes reach opposite poles and begin to decondense, and nuclear envelopes start to reform.
What is cytokinesis in mitosis?
It is the division of the cytoplasm, usually beginning during telophase.
What is interphase in the cell cycle?
It is the period between mitotic divisions, where DNA replication occurs during the S phase.
What happens during the G1 phase of interphase?
The cell grows and carries out normal metabolic activities.
What happens during the S phase of interphase?
DNA replication occurs.
What happens during the G2 phase of interphase?
The cell prepares for mitosis by synthesizing proteins and organelles.
What is a checkpoint in the cell cycle?
A checkpoint is a control mechanism that ensures that a cell has completed necessary processes before progressing to the next stage of the cell cycle.
What is the purpose of the G1 checkpoint?
The G1 checkpoint ensures that the cell has enough resources and energy to begin DNA replication in the S phase.
What is the purpose of the G2 checkpoint?
The G2 checkpoint ensures that DNA replication was successful and that the cell is ready to enter mitosis.
What is the purpose of the spindle checkpoint?
The spindle checkpoint ensures that all chromosomes are properly attached to spindle fibers before the cell enters anaphase.
What happens if a cell fails the G1 checkpoint?
The cell enters a non-dividing state called G0, or undergoes apoptosis (programmed cell death).
What happens if a cell fails the G2 checkpoint?
The cell is prevented from entering mitosis, and DNA repair mechanisms are activated to fix any damage.
What happens if a cell fails the spindle checkpoint?
The cell is prevented from progressing to anaphase until all chromosomes are properly attached to spindle fibers.
How do checkpoint controls work?
Checkpoint controls involve specific proteins that detect DNA damage or incomplete processes, which then halt the cell cycle until the issues are resolved.
What is the significance of checkpoint controls in preventing cancer?
Checkpoint controls prevent damaged or mutated cells from proliferating, which can lead to the development of cancer.
What are some factors that can disrupt checkpoint controls?
Environmental toxins, radiation, and mutations in checkpoint control genes can all disrupt the normal functioning of checkpoints and increase the risk of cancer.
What are the gap phases in the cell cycle?
The gap phases are G1 and G2, which occur between DNA synthesis (S phase) and cell division (mitosis).
What happens during the G1 phase?
During G1, the cell grows and carries out normal metabolic activities, and checkpoint controls ensure that the cell has enough resources and energy to begin DNA replication in the S phase.
What is the duration of G1 phase?
The duration of G1 phase can vary depending on cell type, ranging from a few hours to several days.
What are some factors that can influence the duration of G1 phase?
Factors that can influence the duration of G1 phase include cell size, growth factors, and extracellular matrix signals.
What happens during the G2 phase?
During G2, the cell prepares for mitosis by synthesizing proteins and organelles, and checkpoint controls ensure that DNA replication was successful and that the cell is ready to enter mitosis.
What is the duration of G2 phase?
The duration of G2 phase is typically shorter than G1 phase, ranging from a few hours to a few days.
What are some factors that can influence the duration of G2 phase?
Factors that can influence the duration of G2 phase include the rate of DNA replication, the size of the cell, and the amount of damage in the DNA.
How is the transition from G2 to mitosis regulated?
The transition from G2 to mitosis is regulated by checkpoint controls that ensure that all chromosomes are properly attached to spindle fibers before the cell enters anaphase.
What happens if a cell fails the G1 checkpoint?
The cell enters a non-dividing state called G0, or undergoes apoptosis (programmed cell death).
What happens if a cell fails the G2 checkpoint?
The cell is prevented from entering mitosis, and DNA repair mechanisms are activated to fix any damage.
What is S phase?
S phase is the stage in the cell cycle where DNA replication occurs.
When does S phase occur in the cell cycle?
S phase occurs between the gap phases G1 and G2 and precedes mitosis.
What happens during S phase?
During S phase, DNA helicase unwinds and separates the two strands of DNA, and DNA polymerase synthesizes new complementary strands.
How is DNA replication initiated in S phase?
DNA replication is initiated at multiple sites on the chromosome called origins of replication.
What is the direction of DNA synthesis during S phase?
DNA synthesis occurs in a 5’ to 3’ direction, adding nucleotides to the 3’ end of the new strand.
How are the newly synthesized DNA strands separated during S phase?
The two newly synthesized DNA strands are separated by topoisomerases, which relieve tension in the double helix.
What is the outcome of DNA replication during S phase?
The outcome of DNA replication is two identical copies of the chromosome, called sister chromatids, which are separated during mitosis.
How is the accuracy of DNA replication ensured during S phase?
The accuracy of DNA replication is ensured by checkpoint controls, which detect and repair errors in DNA replication.
What are some factors that can disrupt DNA replication during S phase?
Environmental toxins, radiation, and mutations in genes involved in DNA replication can all disrupt the normal functioning of S phase and increase the risk of cancer.
What is the duration of S phase?
The duration of S phase varies depending on the cell type, but typically lasts for several hours to complete the replication of all chromosomes.
What are the key players in regulating the cell cycle?
The key players in regulating the cell cycle include cyclins, cyclin-dependent kinases (CDKs), tumor suppressor genes, and proto-oncogenes.
What are cyclins?
Cyclins are proteins that are produced and degraded in a cell cycle-dependent manner, and they regulate the activity of CDKs.
What are CDKs? cyclin-dependent kinases (CDKs)
CDKs are enzymes that phosphorylate target proteins to drive cell cycle progression.
How do cyclins and CDKs interact to regulate the cell cycle?
Cyclins bind to and activate CDKs, allowing them to phosphorylate target proteins and drive cell cycle progression.