Cell Cycle Flashcards
What is the cell cycle?
A regulated cycle of division with intermediate growth periods
What are the phases?
Interphase, mitosis or meiosis (nuclear division), cytokinesis.
What happens during interphase?
G1: cell synthesises proteins for replication e.g. tubulin for spindle fibres and cell size doubles
S: DNA replicates = chromosomes consist of 2 sister chromatids joined at centromere
G2: Organelles divide
What is the purpose of mitosis?
It produces 2 genetically identical daughter cells for growth, cell replacement/tissue repair and asexual reproduction. It has 4 stages, prophase, metaphase, anaphase and telophase.
What happens during prophase?
Chromosomes condense becoming visible, centrioles move to opposite poles of cell (animal cells) and mitotic spindle fibres form. Nuclear envelope and nucleolus break down = chromosomes free in the cytoplasm
What happens during metaphase?
Sister chromatids line up at the cell equator, attached to the mitotic spindle by their centromeres.
What happens during anaphase?
Requires energy from ATP hydrolysis. Spindle fibres contract= centromeres divide. Sister chromatids separate into 2 distinct chromosomes and are pulled to opposite poles of cell. spindle fibres break down.
What happens during telophase?
Chromosomes decondense, becoming invisible again. New nuclear envelopes form around each set of chromosomes = 2 new nuclei, each with 1 copy of each chromosome
What happens during cytokinesis?
Cell membrane cleavage furrow forms. Contractile division of cytoplasm.
How is the cell cycle regulated?
By checkpoints which are regulated by cell-signalling proteins, ensure damaged cells do not progress to next stage of cycle.
What does the checkpoint between G1 and S check for?
For DNA damage
After restriction point cell enters.
What does the checkpoint between G2 and M check for?
Cell checks chromosomes replication
What does the metaphase checkpoint check?
That sister chromatids have attached to spindle correctly.
What is meiosis?
A form of cell division that produces four genetically different haploid cells (half number of chromosomes found in parent cell) - gamete’s.
What happens meiosis 1?
Homologous chromosomes pair to form bivalents. Crossing occurs at chiasmata. Cell divides into two. Homologous chromosomes separate randomly. Each cell contains either a maternal or paternal copy.
