Mitosis and meiosis. Flashcards
Describe mitosis.
Occurs throughout the body
DNA synthesis is followed by one cell division, so DNA content stays the same
Used for growth, differentiation, repair, etc.
Leads to two identical diploid cells
What are the stages of mitosis?
PMAT, Cytokinesis
Prophase
Metaphase
Anaphase
Telophase
Cyotokinesis
Describe interphase
90% of cell life span
Chromatin is loosely packed
Chromosomes not visible
Divided into G1, S and G2 phase.
What happens in G1 phase of the cell cycle?
Cell grows and gets ready for DNA synthesis.
What happens in the S phase of the cell cycle?
S-syntheis
DNA replication
What happens in the G2 phase of the cell cycle?
Cell prepares for mitosis
Describe prophase.
Chromatin condenses into visible chromosomes, each has two chromatids joined at the centromere.
Centrosomes migrate to poles, spindle fibres radiate from centrosome.
Mitotic spindle forms in the cytoplasm.
Nuclear envelope dissolves, spindles attach to centromeres via kinetochore.
The chromosomes begin to migrate to the cell centre.
Describe metaphase.
Chromosomes are fully condensed and line up on the equator of the cell at the ‘metaphase plate’
Describe Anaphase.
Centromeres divide and sister chromatids are pulled to opposite poles by shortening of kinetochore fibres.
Describe telophase.
Sister chromatids reach opposite poles and nuclear membrane reforms. The chromosomes decondense and the spindles dissasemble.
What happens in cytokinesis?
Division of the cell into two daughter cells
What is the difference between mitosis and meiosis?
Meiosis only occurs in reproductive cells.
DNA synthesis is followed by two sequential divisions, reducing the chromosome number by half.
Meiosis shuffles the genome.
Meiosis leads to four genetically unique haploid cells(gametes).
Meiosis 1 feature different from mitosis in prophase?
The chromosomes line up side by side in homologous pairs. Crossovers form between chromosomes and recombination takes place
The nuclear membrane disintegrates immediately before metaphase.
Meiosis 1 feature different from mitosis in metaphase?
The chromosomes align at the equatorial plane
Meiosis 1 feature different from mitosis in anaphase?
The homologous chromosomes separate and begin to migrate to the opposite poles of the cell, but the sister chromatids remain together.
