Cell Division & Reproduction Flashcards
two main phases of the cell cycle
growth and division
what happens in growth phases
interphase, cell makes new molecules, cell growth occurs, DNA replication
what happens in division phase
division of the cell’s nucleus (mitosis) and cell division (cytokinesis)
mitosis
the process by which nuclear material is divided during cell division
interphase
the phase when the cell grows and prepares for cell division by duplicating its genetic material (DNA in chromatin replicates)
stages of mitosis
prophase, metaphase, anaphase, telophase
prophase
double chromatin strands shorten and thicken to form chromosomes
nuclear membrane and nucleolus disappear/disassemble
centrioles move to opposite poles of the cell
spindle fibers attach to the centromere of each chromosome
metaphase
the tugging action of spindle fibres pulls the double stranded chromosomes into a line across the middle of the cell (equatorial or metaphase plate)
anaphase
spindle fibres begin to contract and shorten, causing the centromere to be pulled apart
each single stranded chromosome moves to an opposite pole of the cell
telophase
one complete set of chromosomes is now at each pole of the cell
spindle fibres begin to disappear
nuclear membranes begin to form around each set of chromosomes
nucleolus appears in each new nucleus
single stranded chromosomes start to uncoil to form chromatin
cytokinesis occurs forming two daughter cells
cytokinesis in animals vs. plants
animals - cell membrane pinches in from the edges forming a cleavage furrow
plants - a new cell wall forms between 2 daughter cells forming a cell plate
what is meiosis
a type of cell division that occurs in the reproductive organs, which produces sex cells called gametes (egg or sperm)
haploid
containing only one copy of each type of chromosome
diploid
cells containing two copies of each chromosome (one copy from each parent)
homologous chromosomes
chromosomes that contain the same gene sequences but may not be made up of the same alleles
allele
an alternate form of a gene
crossing over
non-sister chromatids in a homologous pair exchange genes
happens in prophase I
random assortment
the random alignment of homologous chromosomes along the equator during metaphase I
zygote
a cell formed by the fusion of two gametes
synapsis
the aligning of homologous chromosomes during prophase I
spermatogenesis
the process of producing male gametes (sperm) in mammals
oogenesis
the process of producing female gametes (eggs) in mammals
monosomy
the loss of a chromosome as a result of non-disjunction
trisomy
the gain of an extra chromosome as a result of non-disjunction
