Lecture 4a: Cell Cycle- Mitosis and Meiosis Flashcards
Cell Cycle (Cell-divison cycle)
The series of events that take place in a cell that causes it to divide into 2 daughter cells (4 processes)
The 4 Coordinated Processes of the cell-divison cycle:
Cell growth, DNA replication, distribution of the duplicated chromosomes to daughter cells, and cell divison
Binary Fission
A means of asexual reproduction in prokaryotes in which a cell divides to form 2 identical organisms
The bacterial cell cycle is divided into 3 stages:
B period: The period extends from the end of cell divison to the beginning of DNA replication
C Period: The period rquired for chromosome replication
D Period: The time between the completion of chromosome replication and the completion of cell cycle
Mitosis
The process in which a eukaryotic cell nucleus splits in 2 (evolved from an early form of binary fission)
The Origin of Replication
The place where DNA replication begins, enabling a plasmid to reproduce itself as it must to survive within cells (once the ori is duplicated, the 2 origins actively migrate to the 2 ends of the cell
The Eukaryotic cell cycle consists of 4 distinct phases:
G1 phase, S phase (synthesis), G2 phase (interphase) and M phase (mitosis and cytokinesis)
- interphase extends from the end of one mitosis to the beginning of the next mitosis. After interphase, mitosis proceeds in 5 stages
Chromosomes
Nuclear units of genetic information that are divided and distributed by mitotic cell divison
Chromatids:
Replication of DNA of each individual chromosome creates 2 identical molecules called sister chromatids
Chromatin
A complex of DNA and proteins that forms chromosomes within the nucleus of eukaryotic cells
Ploidy:
The # of chromosome sets in a cell or species
Diploid (2n)
Haploid (n)
3 phases of the interphase:
- G1 phase (Gap 1 phase, or Growth 1 phase): The cell carries out its function, and in some cases grows
- S phase (Synthesis phase): DNA replication and chromosome duplication occur
- G2 phase (Gap 2 phase, or Growth 2 phase): Brief gap in the cell cycle when cell growth continues and the cell prepares for mitosis and cytokinesis
G0 phase (quiescence) G0 is a resting phase where the cell has left the cycle and has stopped diividing
5 Stages of Mitosis:
- Prophase
- Prometaphase
- Metaphase
- Anaphase
- Telophase
Mitotic Cell Cycle- Chromosome segregation:
The equal distribution of daughter chromomsomes into each of the 2 daughter cells that results from cell divison
Mitotic Cell Cycle- Spindle:
The spindle apparatus is the cytoskeletal strutcure that forms durin cell division to separate sister chromatids between daughter cells. it is composed of hundreds of proteins and microtubules that comprise the most abundant components of the machinery
Mitotic Cell Cycle-Centromere:
The region pf a chromosome to which the microtubules of the spindle attach, via the kinetochore, during cell divison
Mitotic Cell Cycle-Centrosome:
The main microtubule organising center of the cell, which organises the microtubule cytoskeleton during interphase and positions many of the cytoplasmic organelles
Mitotic Cell Cycle-Kinetochore
Are large protein assemblies that connect chromosomes to microtubules of the mitotic and meiotic spindles in order to distribute the replicated gneome from a mother cell to its daughters
Mitotic Cell Cycle- Cleavage furrow
In cytokinesis, a groove that girdles the cell and gradually deepens unitl it cuts the cytoplasm into 2 parts
Mitotic Cell Cycle-Cell plate
New cell walls forms during cytokinesis in terrestial plants. this process entails the delivery of golgi-derived and endosomal vesicles carrying cell wall and cell membrane components to the plane of cell divison and the subsequent fusion of these vesibles within this plate
Prophase:
- Chromosomes condense into compact, rodlike structures
- Each chromosome is doubled as a result of replication
- The centrosome has divided into 2 parts, which are generating the spindle as they separate
- spindle forms in the cytoplasm
Prometaphase:
- Nuclear envelope breaks down
- Spindle enters former nuclear area
- Microtubules from opposite spindle poles attach to 2 kinetochores of each chromosome
Metaphase:
spindle connection and chromosome movement at prometaphase
1. spindle is fully formed and chromosomes align at spindle midpoint
2. Each sister chromatid pair is held in position by opposing forces: the kinetochore microtubules pulling to the poles and the cohesins binding the sister chromatids together
Anaphase:
- separase cleaves the cohesion ring holding sister chromatids together
- spindle separates sister chromatids and moves them to opposite spindle poles
- chromosome segregation is complete
Telophase:
- chromosomes decondense
- return to extended state typical of interphase
- new nuclear envelope forms around chromosomes
- the cytoplasm is beginning to divide by furrowing
Cytokenesis-
the physical process of cell divison, which divides the cytoplasm of a parental cell into 2 daughter cells
