CELL DIVISION Flashcards
Cell Theory
- All organisms are composed of one or more cells.
- The cell is the structural and functional unit of life.
- Cells can arise only by division from preexisting cells
The process by which a parent cell DIVIDES into two or more daughter cells.
Results in the FORMATION OF NEW CELL.
Cell Division
Cell division in non-sex cells or somatic cell is called
MITOSIS
cell division involving sex cells is called
meiosis
basic unit of hereditary; codes for a specific
trait
Gene
the total hereditary endowment of DNA of a cell or organism
Genome
all body cells except reproductive cells
Somatic cell
reproductive cells (sperm & eggs)
Gamete
elongated cellular structure composed of DNA and protein
Chromosome
cellular condition where each chromosome type is represented by TWO homologous chromosomes
Diploid (2n)
cellular condition where each chromosome type is represented by only ONE chromosome.
Haploid (n)
chromosome of the same size and shape which carry the SAME TYPE OF GENES
Homologous chromosome
● The FIRST PART of cell cycle
● It is longer than the M phase
● Considered a RESTING STAGE in cell division
Interphase (non-dividing stage)
● Cells continue to grow
● RNA and protein production
● Produces enough energy for the next steps of the cell cycle
G1 PHASE
● DNA replication
● This results in the formation of two identical copies of the chromosomes called sister chromatids.
● These sister chromatids are joined together by a single centromere.
● Centrosomes also get duplicated during this phase.
S PHASE
● Duplication of organelles
● Protein synthesis
● Preparation for cell division
G2 PHASE
● In this stage cell, ceases growth and protein
production instead, it is now focusing in cell division
● Can either be mitosis or meiosis
M PHASE
● is the process, in the cell cycle, by which a cell DUPLICATES into TWO GENETICALLY IDENTICAL daughter cells.
● it is the division of the SOMATIC (body) cells
● It is the process of forming identical daughter cells by replicating and dividing the original chromosomes.
Mitosis
Mitotic Phases
● Prophase
● Metaphase
● Anaphase
● Telophase
*Chromatic materials THICKEN AND SHORTEN into double stranded chromosomes with two chromatids joined by CENTROMERE.
*The centrioles divide and produce ASTERS (asters are formed only for animal cells)
Prophase
formed only for animal cells
asters
● The MITOTIC SPINDLE, composed of microtubules and proteins, forms in the cytoplasm.
prophase
*The double stranded chromosomes ALIGN themselves at the EQUATORIAL REGION.
Metaphase
*Centromere SEPERATES/SPLIT.
*Single stranded chromosomes migrate to the OPPOSITE POLES
Anaphase
- The chromosomes REACH THE POLES OF THEIR RESPECTIVE SPINDLES.
- Formation of TWO SMALLER CELLS each with exactly the SAME GENETIC INFORMATION. These cells may then develop into different adult forms via processes of development.
Telophase
the chromosomes are CORDONED OFF into distinct new nuclei in the emerging daughter cells
telophase
a groove on the cell membrane BETWEEN THE POLES usually observed in ANIMAL CELLS. It is produce when contractile ring, which is made up of protein, constricts the middle of the cell.
Cleavage furrow
the division of the ORIGINAL CELL’S CYTOPLASM, begins prior to the end of mitosis and completes shortly after telophase. At the end of _______, two genetically identical daughter cells are produced
Cytokinesis
Purposes of Mitosis
- Ensures that the number of chromosomes of the parent cell is identical to its two daughter cells.
- Ensures the growth of offspring.
- Replaces the damaged cells in wounds.
tumor-suppressing proteins that can trigger either cell cycle arrest or apoptosis
p53 protein
p53 protein
Chromosomes 17
cells that undergo continuous division without
stopping.
CANCER
● most important contribution in reproduction.
● also known as REDUCTIVE DIVISION – first division (meiosis I), the cell division involving gametes (sex cells) specifically the sperm and the egg. (The diploid cell is reduced to haploid)
● equational division – second division (meiosis II)
It is a special type of nuclear division which segregates one copy of each homologous chromosomes into each new “gamete”. Sister Chromatids separate, which is a process similar to mitosis
Meiosis
Prophase I
Five stages:
1.Leptotene
2.Zygotene
3.Pachytene
4.Diplotene
5.Diakinesis
chromatins condense and chromosomes appear
Leptotene stage
synapsis (close pairing of the homologous chromosomes) starts.
Zygotene stage
a highly organized protein structure that connects the two homologous chromosomes together.
Synaptonemal complex
● is the PAIRING OF TWO HOMOLOGOUS chromosomes that occurs during meiosis. It allows matching-up of homologous pairs prior to their segregation, and possible chromosomal crossover between them
● This is a CRUCIAL PHASE for meiosis.
● During this phase each pair of chromatids DON’T MOVE to the equator ALONE, they MATCH UP with their homologous pair and fasten together (synapsis) in a group of four called a TETRAD.
Synapsis
crossing over can take place
Pachytene stage
● It is a process in which homologous chromosomes EXCHANGE corresponding segments during prophase I. It gives rise to new combinations of parental alleles among offspring in sexual reproducers.
Crossing-Over
the synaptonemal complex starts to dissolve, and the homologous chromosomes start to process called TERMINALIZATION (separation from
the centromere toward the ends)
Diplotene stage
separation from the centromere toward the ends
TERMINALIZATION
● is the point where two homologous NON-SISTER chromatids exchange genetic material during chromosomal crossover
Chiasmata
the chromosomes become fully condensed and the nuclear membrane disintegrates.
Diakinesis stage
● The chromosomes LINE UP AT THE EQUATOR (metaphase plate) attached by their centromeres to spindle fibers from centrioles.
● Still in homologous pairs
Metaphase I
- The spindle apparatus pulled the chromosomes toward the poles.
- Sister chromatids REMAIN ATTACHED at their centromeres and move as a single unit toward the same pole
Anaphase I
completes the creation of the two haploid daughter cells
Cytokinesis
- BRIEF RESTING PERIOD between telophase I and prophase II
- NO DUPLICATION of chromosomes happen
INTERKINESIS
the SECOND PART of the meiotic process. Mechanically, the process is similar to mitosis, thoughits genetic results are fundamentally different. The end result is production of four haploid cells (23 chromosomes) from the two haploid cells (23 chromosomes, each of the chromosomes consisting of two sister chromatids) produced in meiosis I.
Meiosis II
The four main steps of Meiosis II are:
Prophase II, Metaphase II,
Anaphase II, and Telophase II.
● Chromosomes begin to condense again.
● The nuclear membrane and the nucleolus disappear.
● Spindle fibers begin to form.
Prophase II
● Chromosomes align at the equatorial plate.
● The kinetochores are then attached to the centromere of each sister chromatid.
● Sister chromatids prepare themselves to move at opposite poles.
Metaphase II
● The sister chromatids begin to separate.
● Each sister chromatid moves to the opposite poles.
Anaphase II
● The chromosomes uncoil.
● The nuclear membrane and the nucleolus reappear.
● Cytokinesis finally splits the cells, producing four
haploid cells.
Telophase II
products of meiosis
FOUR
HAPLOID DAUGHTER CELLS
products of mitosis
TWO DIPLOID
DAUGHTER CELLS
● The process of producing gametes, or sex cells.
Gametogenesis
2 types OF Gametogenesis
SPERMATOGENESIS
OOGENESIS
process of producing sperm cells
in males
SPERMATOGENESIS
process of producing egg cells in females
OOGENESIS
