Cell divison Flashcards
Mitosis
Division of genetic material and nucleus
Interphase
Growth stage. Cells grow, DNA is replicated and energy reserves are built
Cytokinesis
Division of the cytoplasm and organelles
Mitosis - Prophase
DNA strands shorten and thicken, chromatin becomes chromosomes, centrioles separate and move to opposite poles of the cell and the nuclear envelope disappears
Mitosis - Metaphase
Chromosomes move to centre of the cell, centromeres align on equator and spindle rivers attach to the centromeres.
Mitosis - Anaphase
Chromatids separate at centromeres and move to opposite poles of the cell. Same number of single copy chromosomes at each pole.
Mitosis - Telophase
Chromosomes at opposite ends of the cell, and they uncondense to form chromatin. Nuclear envelope reappears
Mitosis - cytokinesis
cell membrane pinches to form two distinct daughter cells.
plant cells- cell plate
animal cells - cleavage furrow
Somatic cells
Have DNA from maternal and paternal sides combined making a diploid =2n
humans have 23 different chromosomes, therefore 2(n)=2(23)=46
Gametes
sperm/eggs only hold half the DNA from somatic cells from which they came making haploids=n
humans have 23 different chromosomes,therefore n = 23
Meiosis
Reduces chromosomes number from 2n to n by dividing twice.
Meiosis 1
separates homologous chromosomes
Meiosis 2
Separates chromatids
Meiosis - Prophase 1
chromatin into chromosomes.
centrioles move to opposite poles and spindle fingers appear.
Non sister chromatids connect and trade sections (crossing over)
Meiosis - Metaphase 1
Homologous pairs move to center on either side of the equator. spindle attach to centromeres
Meiosis- Anaphase 1
homologous pairs separate (not sister chromatids)
chromosomes move to opposite poles
23 replicated at each pole
Meiosis - Telophase 1
Chromosomes at opposite ends and do not uncoil to form chromatin.
Meiosis 2- prophase 2
Centrioles move to opposite poles.
New spindle fibers form
Meiosis 2- Metaphase 2
cell moves directly to metaphase
no DNA replication and no formal nucleus.
chromosomes move to center and align on the equator.
Meiosis 2- Anaphase 2
spindle fibers shorten and chromatids pull apart at centromeres.
chromatids move to opposite ends
23 single stranded chromosomes at each pole
Meiosis 2-Telophase 2
Chromosomes at opposite ends.
uncondensed to form chromatin.
nuclear envelope reappears
Why do cells divide
Growth, repair and reproduction
Asexual reproduction
no new combination of cellular materials
