2.9 Cell Growth And Division Flashcards
Cell growth
The process by which cells grow in size
OR
The process by which cell reproduce to increase in number
Gamete
A type of sex cell that has half of the normal DNA found in a somatic cell
Somatic cell
Body cell
Fertilization
Combining of two gametes
Zygote
Result of fertilization, develops into an embryo
Sexual reproduction
Requires two parent organisms or cells. Offspring not identical to parent cells but shares characteristics with each.
Asexual reproduction
Does not require two parent organisms or cells. Offspring genetically identical to parent
Binary fission
Single parent cell double its existing DNA, replicates its internal structures, and divides into two cells. Common in bacteria.
Budding
Occurs when a small growth found on a parent organism splits off and continues growing on its own. Common in yeast.
Fragmentation
Occurs when an existing organism breaks into two or more fragments, which develop into new individuals. Common in plants and some marine animals such as coral, sponges, and sea stars
Parthenogenesis
Occurs when an embryo develops from an unfertilized cell. Common in fish, amphibians, and reptiles
Parent cell
The original cell that divides during cell division
Daughter cell
Two are produced by the parent cell during cell division
Cell cycle
Series of events that lead to the duplication of the DNA in the cell and subsequent division of the DNA and the cytoplasm to produce two daughter cells
Meiosis
Cell division that results in four genetically distinct cells each with half the number of chromosomes of the parent cell
Involved in sexual reproduction only
Mitosis
Cell division that results in two cells that are genetically identical and have the same number of chromosomes as the parent cell
Primarily involved in the growth and maintenance of organism systems and asexual reproduction
Chromosome
Consists of two identical chromatids called sister chromatids bound together by a centromere
Interphase (S) stage
The time when the cell isn’t dividing but may be growing and replicating DNA
Has three phases including
- G1 phase (first gap)
- S phase (synthesis of DNA)
- G2 phase (second gap)
Precedes mitotic (M) phase
Mitotic (M) phase
Relatively short phase that includes
- prophase
- metaphase
- anaphase
- telophase
Prophase
Step 1 of the Mitotic phase
The cell has no nuclear envelope and prepares to divide by tightly condensing its chromosomes which pair up
- spindle fibers emerge and chromosomes condense, becoming visible
- the nucleolus disappears
- the nuclear envelope breaks down
Metaphase
Step 2 of the mitotic phase
Cell begins to elongate and chromosomes line up along the center of the cell
- mitotic spindle fully developed and centrosomes form at opposite poles of the cell
- chromosomes line up at the metaphase plate
- sister chromatids attach to the spindle fiber
Anaphase
Step 3 of the mitotic phase
Cell continues to elongate and the chromosomes are pulled apart
- sister chromatids break down
- chromosomes (formerly sister chromatids) move toward poles of the cell
- a cleavage furrow starts to appear
Telophase
Step 4 of the mitotic phase
Cell develops a nuclear envelope and begins to pinch in the middle
- chromosomes start to form a normal, jumbled arrangement
- a nuclear envelope surrounds the chromosomes
- the mitotic spindle breaks down
G1 phase
Cell accumulates the building blocks necessary to duplicate the chromosomes
S phase
DNA replication occurs and sister chromatids are created. They are held together by two centrosomes to make a mitotic bundle that facilitates chromosome movement
G2 phase
Cell accumulates necessary materials for the movement of chromosomes, duplicating important organelles. In this phase the cell may grow.
Cytokinesis
Division of the cytoplasm of a parent cell to form two new cells. Starts in anaphase and ends shortly after telophase.
Diploid
Cell that has two sets of chromosomes
Haploid
Cell with a single set of chromosomes
Meiosis I
Number of chromosomes is halved
Consists of
- prophase I
- metaphase I
- anaphase I
- telophase I
Meiosis II
Generates two more haploid cells from duplicated sister chromatids present in the daughter cells of meiosis I
Interphase I
Occurs before Meiosis I
Very similar to interphase that precedes mitosis
Synapsis
Homologous counterparts line up next to each other along the full length of the chromatids
Crossing over
Exchange of genetic material between homologous chromosomes during synapsis
Synapse
Two homologous chromosomes joined together
Chiasma
The point at which chromosomes cross over
Recombinant DNA
DNA developed by crossing over
Prophase I
- sister chromatids are formed
- a synapse forms
- DNA crosses over during the chiasma
- recombinant DNA forms
Metaphase I
- homologous chromosomes arrange themselves at the metaphase plate randomly; this is another source of genetic variation
- spindle fibers attach to chromosomes
Anaphase I
Spindle fibers pull apart the homologous chromosome pairs
Telophase I
- the nuclear membrane reforms and chromosomes regain their jumbled arrangement
- a cleavage furrow forms
- two haploid daughter cells form with one chromosome set
Prophase II
- chromosomes condense to reform the x-shapes
- the nuclear envelope breaks down if it has reformed. Centrosomes move to poles of the cell
- spindle fibers emerge and attach to sister chromatids
Metaphase II
- sister chromatids line up at the metaphase plate
- spindle fibers prepare to pull apart sister chromatids
Anaphase II
- sister chromatids are separated
- a cleavage furrow begins to form
Telophase II
- nuclear membrane reforms
- chromosomes become more jumbled
- cleavage furrow forms and cytokinesis occurs
- four haploid cells that are genetically distinct are produced with a single chromatid
Checkpoints
One mechanism that cells use to minimize the risk of error during the cell cycle
G1 checkpoint
Determines if cell is capable of dividing based on the following factors
- size
- DNA integrity
- nutrient level
- molecular signaling (is the cell receiving positive external support, such as growth hormones)
G2 checkpoint
Ensures that none of the DNA is damaged and that it replicated properly during interphase
Cell cycle is halted to allow for repairs. If irreparable, the cell will undergo apoptosis
Apoptosis
Programmed cell death
M checkpoint
Aka spindle checkpoint
Cell assesses whether the spindle fibers are properly attached to the sister chromatids
Cell cycle regulators
Contribute to the signals that determine whether the cell should proceed past a checkpoint
Cyclins
Several types of proteins, each associated with a different phase or checkpoint within the cell cycle.
Cyclin-dependent kinases
Will signal that the cell is ready to move on to the next stage of the cell cycle after a cyclin binds to it..
Cancer
Cell division proceeds in an uncontrolled manner, often due to malfunction of a cell cycle regulator or a checkpoint being ignored
