Cell Division Flashcards
Chapter 4, Pt 1
What is the cell cycle?
The sequence of events by which a cell duplicates its genome, synthesizes the other constituents of the cell and divides into two daughter cells.
What is cell division?
Cell division is the process by which a single cell divides into two or more daughter cells.
What is Interphase?
The phase between two successive M phases
Consist of
-G0 phase
-G1 phase
-S phase
-G2 phase
What is the G1(Gap 1) phase?
The phase where the cell is metabolically active but does not replicate it DNA
What is the S (Synthesis) Phase
The period in which DNA synthesis/replication takes place.
What is the G2 (Gap 2) Phase
The phase in which proteins are synthesized in prep for mitosis.
What is the G0 (Quiescent) Phase
The phase in which cells that do not divide further exit G1phase to enter an inactive state.
M (Mitosis) Phase
The phase in which actual cell division occurs
-Starts with karyokinesis and ends with cytokinesis
Split into Prophase, Metaphase, Anaphase, and Telophase (PMAT).
What occurs during prophase?
The phase in which chromatin in the nucleus condenses into chromosomes, centrioles move towards opposite ends of the cell, and nuclear membrane come apart.
What is a homologous chromosome?
Homologous chromosomes are chromosome pairs that have the same genes but may carry different versions (alleles) of those genes.
What is metaphase?
The phase in spindle fibers attach to kinetochores and chromosomes are moved to the metaphase plate
What is the metaphase plate?
The plane of alignment the chromosomes.
What is a centromere?
The structure that holds sister chromatids together.
What is a kinetochore?
They are disc-shaped structures at the surface of centromeres that function in the attachment of spindle fibers.
What is Anaphase?
The phase in which centromeres split, and chromatids separate, moving to opposite poles.
What is Telophase?
The phase in which chromosomes decondense into chromatin, nuclear envelope reforms, and membrane-bound organelles reform
What is Cytokinesis?
The phase in which the cell itself is divide into two daughter cells
How does Cytokinesis occur in Animal Cells?
Cytokinesis occurs by the appearance of a furrow in the plasma membrane, the furrow deepens and ultimately joins in the center dividing the cytoplasm into two
How does Cytokinesis occur in Plant Cell?
Cytokinesis occurs by the formation of a wall in the center of the cell and grows outward to meet the existing lateral walls
What is a Cell-Plate?
A simple precursor that represents the middle lamella between the wall of two adjacent cells.
What is the Significance of Mitosis?
-Results in the production of diploid daughter cells
-Responsible for the growth of multicellular organisms
-Restores the nucleo-cytoplasmic ratio
-Important in cell repair
What happens when karyokineses is not followed by cytokinesis?
In some organisms this leads to the formation of syncytium
(e.g. liquid endosperm in coconut)
What is Meiosis?
A specialized kind of cell division that results in the production of haploid daughter cells
What are the special characteristics of Meiosis
-Involves two sequential cycles of nuclear division (Meiosis I & II)
-Involves the pairing of homologous chromosomes and recombination between them
-Four haploid cells are formed at the end of meiosis II
What occurs during Prophase 1
-Leptotene
-Zygotene
-Pachytene
-Diplotene
-Diakinesis
What is Leptotene?
The stage in which chromosomes become visible under a light microscope.
What is Zygotene?
The stage in which chromosomes start pairing together in a process of association called synapsis
What is the Synaptonemal Complex
The complex structure is formed that accompanies the chromosome synapsis.
What is a Bivalent (Tetrad)?
The complex formed by a pair of synapsed homologous chromosomes
What is Pachytene?
The stage in which recombination nodules appear and recombination occurs leaving the chromosomes linked at the sites if crossing over (chiasmata)
What enzyme is involved in crossing over
Recombinase
What is a recombination Nodule?
The sites at which crossing over occurs between non-sister chromatids of homologous chromosomes
What is Crossing Over?
The exchange of genetic material between homologous chromosomes
What is Diplotene?
The stage in which the synaptonemal complex dissolves and recombined homologous chromosomes of the bivalents separate except at the site of crossing over
What are Chiasmata?
Points where homologous chromosomes exchange genetic material during meiosis.
What is Diakinesis?
The stage in which the chiasmata are terminated, and chromosome fully condense.
What is Metaphase I?
The bivalent chromosomes align on the equatorial plate, and spindles attach the pair of homologous chromos es
What is Anaphase I?
The stage in which the homologous chromosome separate, while sister chromatids remain associated at their centromeres
What is Telophase I?
The stage in which nuclear membrane and nucleolus reappears, and cytokines follows forming a diad of cells
What is Interkinesis?
The short livid stag between the two meiotic divisions
What is Prophase II?
The phase in which chromatin in the nucleus condenses into chromosomes, centrioles move towards opposite end of the cell, and nuclear membrane breaks come.
What is Metaphase II?
The phase in spindle fibers attach to kinetochores and chromosomes are moved to the metaphase plate
What is Anaphase II?
The phase in which centromeres split, and chromatids separate, moving to opposite poles.
What is Telophase II?
The stage in which nuclear membrane and nucleolus reappear, and cytokines follow resulting in the formation of four haploid daughter cells
what are the significances of Meiosis?
-The method by which a specific number of chromosomes is conserved
-Increase the genetic variability in a population
