cell division Flashcards
(31 cards)
what happens in interphase of mitosis?
G1 (growth, protein synthesis, organelle number increases rapidly)
S (synthesis and DNA replicates)
G2 (second growth phase, proteins synthesis)
why do cells need to divide?
for asexual reproduction
living things to produce more cells and grow
repair damaged tissues
replace worn out cells
what does a condensed chromosome contain?
chromatid
centromere
arms
(doubled, coiled, short)
what is a chromatin?
long, tread-like DNA in non-dividing cells
what is a chromosome?
double, coiled, short DNA in dividing cells
what does duplicated DNA look like?
2 identical sister chromatids attach in middle
how many chromosomes do humans have?
46
23 pairs
what happens in step 1 of mitosis (interphase)?
DNA replicates
organelles replicate
cells grow
(longest stage)
what happens in step 2 of mitosis?
division of 2 nuclei
each have same number of chromosomes
each new daughter cell has nucleus with complete set of chromosomes
why is mitosis significant?
allows production of cells which are genetically identical so gives genetic stability
leads to growth
repair of damaged tissues
replacement of dead cells
what happens in prophase of mitosis?
chromosomes coil/condense
nuclear envelop and nucleolus disappear
centrioles move to opposite sides of nucleus
spindle fibres form
what happens in metaphase of mitosis?
chromosomes arrange themselves on equator of spindle
microtubules attach to centromeres
what happens during anaphase of mitosis?
centromere divides in two
microtubules contract and pull chromatids to opposite poles of cell
chromatids are now called daughter chromosomes
what happens during telophase of mitosis?
daughter chromosomes reach poles and uncoil and lengthen
nuclear envelope and nucleolus reforms
2 new nuclei are formed
what happens during cytokinesis?
chromosomes are now chromatins
division of rest of the cell occurs (cytoplasm and organelles)
cell returns to interphase
what is the link between mitosis and cancer?
damage via radiation causes damage to cell cycle genes so cells cannot divide
mutation of cell cycle genes can form tumor
cancerous cells prevent normal cells from functioning
what is a homologous pair of chromosomes in meiosis?
one chromosome from mother and one from father
contain same genes but different alleles
what are gametes?
specialised cells containing half number of chromosomes needed to produce a zygote
contain haploid number of chromosomes
what does a diploid cell contain?
cell contains homologous chromosomes
what does a haploid cell contain?
cell contains one of each chromosomes
what are somatic cells?
cell which contains diploid number of chromosomes
what does meiosis produce?
4 haploid cells (contain one set of chromosomes )
what happens during prophase I?
chromatin condenses
chromosomes are now two chromatids
homologous pairs of chromosomes come together
crossing over takes place between sister chromatids in bivalent
at point of crossing over is called chiasma
what does crossing over do?
results in recombination of maternal and paternal genetic information
