Chapter 3.7: Cell Division Flashcards
Two types of cell division
Somatice and reproductive
A somatic cell
Any cell in the body other than a germ cell
A germ cell
a gamete (sperm or oocyte) or any precursor cell distined to become a gamete
This type of cell division, the cell undergoes a nuclear division called mitosis and a cytoplasmic division called cytokinesis
Produces two genetically identical cells
Somatic cell division
The cell divison that produces gametes,
Reproductive cell division
Special two step division that produces two cells, each with half the DNA of the original cell
Meiosis
Two chromosomes that make up a pair
Homologous chromosomes
What do we call the orderly sequence of events in which somatic cells duplicates its contents, and divides in two?
The cell cycle
What do diploid cells contain?
Two sets of chromosomes
The two major periods of the cell cycle
Interphase and mitotic phase
Interphase
When a somatic cell is not dividing
Mitotic Phase (M)
When a somatic cell is dividing
What phase is the time that cell does most of its growing?
Interphase
What are the 3 phases of interphase?
G1 (Gap phase)
S (synthesis of DNA)
G2 (Gap )
What happens during G1 phase of interphase of a somatic cell?
interval between mitotic phase and S phase.
Most organelles cystolic components are replicated
High metabolic activity
Very short in embryonic cells and cancer cells (rapid growing cells)
What is G0 phase?
Cells that remain in G1 for a long time and possibly may not replicate again
What is the S Phase of interphase?
Between G1 and G2
Lasts about 8 hours
DNA is replicated
What is the G2 phase?
The gap of interphase between S phase and the start of the mitotic phase
Approx 4-6 hours
Cell growth continues, enzymes and other proteins needed are synthesized for cell division, replication of centrosomes are completed
This phase of cell divison of somatic cells results in the formation of two identical cells and consists of two divisions - nuclear (mitosis) and cytoplasmic (cytokinesis)
Mitotic Phase
The distribution of two identical sets of chromosomes into two seperate nuclei
Process consists of 4 stages
Mitosis
The 4 stages of mitosis (nuclear division)
- Prophase
- Metaphase
- Anaphase
- Telophase
Prophase
- chromatin fibres condense and shorten
- Each chormosome consists of a pair of chromatidss
- chromatids held together by centromere
- pericentriolar material of centrosomes start to form mitotic spindle
- microtubules push centrosomes to poles of cell
- nucleolus disappears and envelope breaks down
Metaphse
the microtubules of the mitotic spindle align the centromeres of the chromatid pairs at the exact center of the mitotic spindle
The plane of alignment of the centromeres
metaphase plate
Anaphase
- centromeres splie, separating the halves of the chromatid pair which move towards opposite sides of cell
- ## chromatids now called chromosomes
Telophase
Final stage
-begins once movement of chromosomes stops
- chromosomes at opposite ends of cell are identical and uncoil and revent to the threadlike chromatin form
- new nuclear envelopes form around each mas
- mitotic spindle breaks up
Part of mitotic phase
Involves division of cytoplasm and organelles into two identical cells
Begins in late anaphase with formation of cleavage furrow
Cytokenesis
Three possible destinies of cells
- Remain alive and functioning without dividing
- To grow and divide
- to die
Contractile ring in cytokenesis
Actin microfilaments that pulls the plasema membrane progressively inwards; eventually pinches the cell into two
Normal type of cell death
apoptosis
pathalogical type of cell death
necrosis
Reproductive cell division of sex cells that produces gametes in the gonads and results in cells with half the chromosomes
Meiosis
What are the two stages of meiosis
Meiosis 1
Meiosis 2
What are the four stage of Meiosis I
- Prophase I
- Metaphase I
- Anaphase I
- Telophase I
Crossing over
exchanging of parts between non sister chromatids
synapsis
two sister chromatids of each pair of homologous chromosomes pair off
tetrad
the resulting four chromatid structure of synapsis
Formation of new combinations of geners unlike the starting cell that produced them?
Genetic recombination
Metaphase I
The tetrads line up on the metaphase plate
Anaphase I
each pair is split as pulled in opposite directions by the microtubules attached to the centromeres
Telephase I and cytokenesis of Meiois
similar to these phases in somatic cell division
Haploid cell
the resulting cell from Meiosis I becaue it contains only half the number of chromosomes as the original cell
Meiosis II phases
Prophase II
Metaphase II
Anaphase II
Telophase II
Result of Meiosis
4 haploid gametes that are genetically different
