Chapter 11: Cell cycle and division Flashcards
Cell activities during interphase
- carry out DNA replication
- carry out their functions
- synthesize new organelles
- grow to its maximum size
Mitosis - Prophase
Chromosomes thicken and shorten and become visible under a microscope.
Nuclear membrane disintegrates.
Mitosis - Metaphase
Chromosomes move to the middle of the cell
Spindle fibres attach to the centromere of the chromosomes
Mitosis - Anaphase
Spindle fibres contract.
**Sister chromatids **move to the 2 opposite poles of the cells
Mitosis - Telophase
Chromosomes uncoil to form chromatin again
A new nuclear membrane is formed around each group of chromosomes
Meiosis I - Prophase I
Chromosomes thicken and shorten and become visible under a microscope.
Nuclear membrane disintegrates
Homologous chromosomes pair up.
Crossing over may occur.
Meiosis I - Metaphase I
Homologous chromosomes line up in the middle of the cell randomly (Independent assortment occurs)
Spindle fibres attach to the centromere of the chromosomes
Meiosis I - Anaphase I
Spindle fibres contract.
Homologous chromosomes move to the opposite poles of the cells
Meiosis I - Telophase I
A new nuclear membrane is formed around each group of chromosomes
Meiosis II - Prophase II
Chromosomes thicken and shorten and become visible under a microscope.
Nuclear membrane disintegrates.
Meiosis II - Metaphase II
Chromosomes move to the middle of the cell
Spindle fibres attach to the centromere of the chromosomes
Meiosis II - Anaphase II
Spindle fibres contract.
Sister chromatids move to the 2 opposite poles of the cells
Meiosis II - Telophase II
Chromosomes uncoil to form chromatin again
A new nuclear membrane is formed around each group of chromosomes
Crossing over (Meiosis)
Matching regions of chromosomes cross over each other to form X-shaped structures called chiasma
At the chiasma, chromosomes break, exchange corresponding parts and rejoin
Independent assortment (Meiosis)
Homologous chromosomes line up in the middle of the cell randomly
Each pair of homologous chromosomes sort paternal chromosome and maternal chromosomes into daughter cells independent of the other pairs of chromosomes
Mitotic cell division VS Meiotic cell division: Genetic composition of daughter cells
Mitotic: Daughter cells are genetically identical to the parent cell and to each other
Reason:
- Interphase before cell division) DNA replication occurs
- Metaphase) Chromosomes line up at the middle of the cell
Identical sister chromatids are separated and divided equally into 2 daughter cells
Meiotic: Daughter cells are genetically different due to crossing over and independent assortment in Meiosis I
Mitotic cell division VS Meiotic cell division: number of daughter cells and number of chromsomes of daughter cells
Number of daughter cells
Mitotic: 2 (1 division)
Meiotic: 4 (2 divisions)
Number of chromosomes of daughter cells (parent cell: 2n)
Mitotic: 2n // diploid // same as parent cell
(homologous chromosomes do not separate)
Meiotic n // haploid // half of parent cell
(homologous chromosomes separate)
Mitotic cell division VS Meiotic cell division: Significance
Mitosis:
For growth and repair, asexual reproduction
Meiosis:
* Form haploid gametes so that the diploid number of chromosomes can be restored after fertilization
* Result in (note: not increase) genetic variation to increase the chance of survival when environmental conditions change
Mitotic cell division VS Meiotic cell division: Site of occurence
Mitotic:
Most body cells (except gametes, RBCs and xylem)
Meiotic:
- Humans: testes, ovaries
- Plants: anthers, ovules
Cytokinesis: Animal cell
Cell membrane constricts inwards until the cell spilts into two
Cleavage furrow is formed
Cytokinesis: Plant cell
Cell plate
