3.2.2 - all cells arise from other cells Flashcards
what do eukaryotic cells which retain the ability to divide do?
show a cell cycle
what are the two main stages of the cell cycle?
interphase and mitotic (M) phase
what happens during interphase?
DNA replication occurs (chromosomes become two sister chromatids joined by centromere), chromosomes can’t be seen but see chromatin instead
what are the stages of interphase?
- G1 - stage of cell growth focusing on synthesis of proteins and organelles
- S - DNA is replicated
- G2 - synthesis of proteins specific to mitosis
what happens during mitosis?
a eukaryotic cell divides to produce two daughter cells, each with the identical copies of DNA produced by the parent cell in DNA replication
what are the four stages of mitosis?
prophase, metaphase, anaphase, telophase
what happens during prophase?
chromosomes condense and become visible
pair of centrioles move to each pole of cell
nucleolus disappears and nuclear membrane breaks down
what happens during metaphase?
mitotic spindle forms and connects centrioles to chromosomes
chromosomes line up along equator of cell
what happens during anaphase?
centromeres split in two allowing chromatids to separate
spindle fibres shorten pulling chromatids towards opposite poles of cell
what happens during telophase?
chromatids reach poles of cell (now chromosomes)
spindle fibres break down
nuclear membranes form and nucleoli appear to create two new nuclei
what happens during cytokinesis in animal cells?
a ring of actin filaments form around the equator of the cell then tighten to form a cleavage furrow, splitting the cell in two
what happens during cytokinesis in plant cells?
vesicles move to the equator, line up and fuse to form two membranes called the cell plate - a new cell wall is laid down between the membranes which fuses with the existing cell wall
why do plant cells carry out cytokinesis differently to animal cells?
they have a cell wall which can’t be broken
