Chapter 12 Cell cycle Flashcards
Cell cycle
Life cycle of a cell
What are the stages of the cell cycle in eukaryotic cells (cells with a nucleus)
Interphase and mitotic phase
What happens in interphase
The cell grows and makes a copy of its DNA
What happens in G1 phase
The cell grows physically larger,
Copies organelles
What happens in S phase
The cell synthesizes a complete copy of the DNA in its nucleus
Duplicates a microtubule-organizing structure called the centrosome which helps division during mitosis
What happens during G2 phase
The cell grows more,
Makes proteins and organelles
What are the 3 stages of interphase
G1, S, and G2 phase
What happens in the M phase and what are its processes
Cell divides its copied DNA and cytoplasm to make two new cells
Two parts processes are mitosis and cytokinesis
What happens in Cytokinesis and where does it take place
The cytoplasm of the cell is split in two making two new cells. w
Cytokinesis in animal cells
Contractile cytokinesis pinches the cell in two making the cleavage furrow
Cytokinesis in plant cells
Plant cells divide in two by the cell plate that forms in the middle
What is the G0 phase
Its where cells that do not divide that exit the G1 phase, enters a resting phase called G0 phase.
What is mitosis
Process where one mother cell produces 2 daughter cells that are identical to itself that each have a full pair of chromosomes
What is the process of cytokinesis and in what stage of mitosis does it start
process of dividing the cell contents to make two new cells
Starts in anaphase or telophase
Sister chromatids
two identical chromatids that are formed by replication of a chromosome during the S phase of the cell cycle, are joined by a centromere, and segregate into separate daughter cells during anaphase
What happens in early prophase
- Chromosomes start to condense
- Mitotic spindles form
- Centrosomes move towards opposite sides of the cell
What happens in prometaphase
- Nuclear envelope disappears
- Mitotic spindle grows more
Centromeres
Regions of DNA where the sister chromatids are most tightly connected
Kinetochore
Patch of protein found on the centromere of each sister chromatin that microtubules bind to at chromosomes
Aster
Cellular structure is shaped like a star, formed around each centrosome during mitosis in an animal cell
Kinetomicrotubules
A part of the mitotic spindle that is able to bind to the kinetochores
Metaphase
At this stage the spindle captured all the chromosomes and lined them up at the middle of the cell
- All chromosomes align at the metaphase plate
- The kinetochores are attached to the microtubules
Spinal checkpoint
Cell checks to make sure the chromosomes are at the metaphase plate with their kinetochores correctly attached to microtubules
Telophase
Chromosome decondense and return to stringy form
Mitotic spindle breaks down
Nuclear envelope redevelops
What happens in anaphase
Chromatids are split apart and pulled to the opposite ends of the cell by the kinetochore microtubules
Each chromatid is now their own molecule
What do motor proteins do in mitosis
Drives all the processes of mitosis
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Cleavage furrow
Divides the cytoplasm to create split a cell into two new ones using a pinch
Cell plate
Structure that forms down middle of the cell and splits it into two daughter cells separated by a new wall
DNA
genetic material of all organisms and found in cells
Every cell that divides passes a copy of its DNA to each of its daughter cells
Genes
Units in which DNA is organized and genes give instructions for making proteins
Nucleoid
Central region of the cell which has the most DNA. Functions like the nucleus but without a membrane
Genome
cell’s set of DNA
Histones
Specialized proteins that organize DNA and give it structure in eukaryotic cells.
Determines which genes are active
Chromatin
the combination of DNA and proteins that make up the genetic material of chromosomes.
Chromosomes
Threadlike structures made of protein and single molecule of DNA
Diploid (2n)
Has 46 chromosomes, has paired sets of chromosomes called homologous chromosomes
Haploid (1n)
Contains one homologous chromosome from each pair.
Has 23 chromosomes
Examples are sperm and eggs
Cohesins
Proteins that attach sister chromatids to each other
gametes
sex cells, sperm and eggs
Meiosis
Process where a single cell divides twice to produce four cells containing half the original amount of genetic information
sister chromatids
One-half of the duplicated chromosome that’s formed by DNA replication of a chromosome.
Homologous chromosomes
Similar but nonidentical chromosome pairs an organism receives from its two parents
Essentially same gene, loci (genetic position, centromere location and chromosomal length. They only differ in alleles.
Meiosis I
Homologoue pairs seperate during a first round of cell division
Meiosis II
Sister chromatids separate during a second round.
Prophase I
The chromosomes condense but each chromosomes also pairs up with its homologous partner
Crossing over occurs: Homologous chromosomes trade parts
Synaptonemal complex
Holds homologues together.
Metaphase I
Spindle captures chromosomes
homologue pairs line up at the metaphase plate for separation
Each chromosome attaches to the microtubules from just one pole of the spindle
Anaphase I
The spindle fibers shorten and pull each homologous chromosome to one side
Homologous are pulled apart and move to opposite ends of the cell
Telophase I
Chromosomes arrive at opposite poles of the cell.
The nuclear envelope develops again
Chromosomes decondense
Meiosis II
“Mitosis for haploid cells”
prophase II
chromosomes condense and nucleur envelope breaks down
When the centresomes move apart, the spindle forms between them
metaphase II
chromosomes line up individually along the metaphase plate
Anaphase II
Sister chromatids separate and are pulled towards the opposite poles of the cell
Telophase II
Nuclear membranes form around each set of chromosomes and the chromosomes decondense
Cytokinesis in meiosis 2
Splits the chromosome sets into new cells, forming the final products of meiosis which are four haploid cells in which each chromosome has just one chromatid. Also each cell has half the chromosomes and a fourth of DNA of the parent cell
Where does mitosis occur
Somatic cells
Where does meiosis occur
Germ cells
Difference between meiosis I and meiosis II
Pairs of homologous chromosomes are separated during meiosis I while sister chromatids are separated during meiosis II
How are mitosis and meiosis similar
Sister chromatids segregate during both mitosis and meiosis. This occurs in anaphase of mitosis and anaphase II of meiosis
Three importance checkpoints in the cell cycle
G1 checkpoint at G1/S transition
G2 checkpoint at G2/M transition
The spindle checkpoint, at the transition from metaphase to anaphase
G1 checkpoint
controls the commitment of eukaryotic cells to transition through the G1 phase to enter into the DNA synthesis S phase.
G2 checkpoint
prevents cells from entering mitosis when DNA is damaged
M checkpoint (spindle checkpoint)
Cell examines whether all sister chromatids are correctly attached to the spindle microtubules
Cyclin
regulatory subunits of CDK complexes that control the progression through cell cycle checkpoints by phosphorylating and inactivating target substrates
Cyclin-dependent kinases
Family of enzymes that can be activated if its binded with cyclin. After activation it modifies target proteins
kinases
enzymes that phosphorylate (attach phosphate group to specific target proteins
maturation-promoting factor (MPF)
G2 checkpoint regulates a cell from the G2 growth phase to the M phase
How does cyclin levels change throughout the cell cycle
Stays at low levels for much of the cell cycle and builds up as the cell approaches G2 and M transition
