3 - CELL CYCLE Flashcards
why do cells divide?
- reproduction
- tissue renewal
- growth and development
what structures divide during cell division?
- DNA
- chromosomes
- nucleus
4 stages of interphase
g1, s, g2, g0
- normal metabolic activity
- number of cell organelles increases to normal levels and the volume of cytoplasm increases too, eventually reaching mature size
- a cell can remain in this phase indefinitely
- doubling of number of cell organelles
- stage of the cycle where cells stay the longest
g1 phase
- Synthesis phase
- DNA and chromosomes replicate inside the nucleus (92 chromosomes / 46 pairs)
s phase
- Structures directly involved in mitosis develop
- Preparation phase for cell division
g2 phase
- Time-out phase
- Can last for years
- Cells may die, proceed to cell division, or remain specialized
g0 phase
When Do Chromosomes Duplicate?
- During the S phase, all the chromosomes duplicate
- When a chromosome duplicates, it produces a replica chromosome referred to as chromatid/sister chromatid
where are the sister chromatids joint?
centromere (specifically kinetochore)
- The mechanism by which somatic eukaryotic cells produce identical daughter cells
- Produces 2 identical diploid daughter cells
- Involved partition of both cytoplasmic
mitosis
four phases of mitosis
- prophase
- metaphase
- anaphase
- telophase
- Chromatin condenses into chromosomes by dehydrating and coiling
- 1 chromosome pair = 2 sister chromatids
- Pairing of chromatids happens in this phase
- Nucleolus and nuclear envelope begins to disappear
- Centrosomes divide into 2 centrioles pair, move apart, forms spindle fiber
prophase
- During ________, the chromosomes align near the center of the cell called equator
- The movement of chromosomes is regulated by the attached spindle fibers
- Motion similar to tug-of-war
- Longest stage of mitosis
metaphase
- The centromere dissolves and releases each chromatid to be pulled by the spindle fibers via the kinetochore
- At the end, each set of chromosomes has reached an opposite pole of the cell, and the cytoplasm begins to divide.
- Shortest stage of mitosis
anaphase
- Chromosomes in each of the daughter cells become organized to form two separate nuclei, one in each newly formed daughter cell
- Cleavage furrow forms preparing for complete division
telophase
After telophase, the mother cell splits into 2 and produces 2 daughter cells by undergoing?
cytokinesis
mitosis control checkpoints
- DNA damage checkpoints
- apoptosis checkpoint
- spindle assembly checkpoint
checkpoint that happens during s phase
DNA damage checkpoint
- Survivins ensure that mitosis continues instead of apoptosis
- As mitosis begins
apoptosis checkpoint
checkpoint that happens during metaphase
Spindle assembly checkpoint
uncontrollable cell / continuously dividing cells spread out throughout the body
Metastatic spurt
- Specialized type of cell division which reduces the chromosome number by half
- This process occurs in all sexually reproducing eukaryotes both single-celled and multicellular including animals, plants, and fungi
meiosis
end of meiosis 1
2 daughter cells with 46 chromosomes each and are no longer identical due to recombinant chromosomes
tetrad formation and crossing over
Prophase I
Each sister chromatid will link with their homologous chromosome
tetrad formation
Interchange of genetic material between homologous chromosomes occurring during Prophase I
crossing over
- Tetrads line up at the equator
- 1 sister chromatid is pulled to each polar end
metaphase I
- Tetrads line up at the equator
- 1 sister chromatid is pulled to each polar end
- Upon separation of each sister chromatid, 1 will result to a unique sister chromatid
anaphase I
- Nuclear envelopes partially assemble around chromosomes
- Spindle disappears
- Cytokinesis divides the cell into two
telophase I
Interchange of genetic material between homologous chromosomes occurring during Prophase I
crossing over
Same as prophase except:
Sister chromatids are now recombinant
prophase II
Each sister chromatid lines up at the equator (2)
Metaphase II
- Each individual chromosomes are pulled to opposite poles
- Each developing cell will only get 1 copy of each chromosome
Anaphase II & Telophase II
Haploid sperm cell and oocyte are derived from
diploid germ cells
process of developing haploid cells (N or 23 chromosomes)
meiosis
begins with double number of chromosomes and ends up with 2 diploid cells
first meiotic division
reduction of chromosome number since each of the cells from the first division divides again = 4 cells
second meiotic division
Substances that may produce physical or functional defects in the human embryo or fetus after the pregnant woman is exposed to the substance
teratogens
period where the pregnant woman is most vulnerable to teratogens
1st trimester
most common teratogens
Tobacco and cannabis
Arsenic and benzene
Caffeine and alcohol
