Cell cyle and dvision Flashcards
what is disjunction
seperation of homologous pair of chromosome during the anaphase I of meisosis is called disjunction or segregation
what does recombinase do
it acts as a cutting and pasting/ligating of dna molecules enzyme
who proposed the term meiosis
Term Meiosis was proposed by Farmer and Moore.
what are meiocytes
the cells thatundergo meiosis to produce gametes.
Responsible for transmission of hereditary information from
generation to generation.
*Meiosis ensures the production of haploid phase in the life cycle of
sexually reproducing organisms whereas fertilization restores the
diploid phase.
what is the other name for reductional division and equatuonal division
heterotypic-> reductional
homotypic-equational
why is leptotene called as the ‘bouquet stage’
It is because the chromomes are thin and long and are arranged like a bouquet shape.
what is amitosis
It is a simple form of cell division without the formation of
spindle.
*Cell division by simple cleavage of the nucleus and division of the
cytoplasm without spindle formation or appearance of chromosomes.
*Majorly occurs in lower organism.
*Also called as direct cell division or binary fission.
what is astral and anastral division
in animals, centrioles are present and hence asters and astral rays are formed and so it is astral divsion.
However in higher plants, there are no centiroles and hence no asetrs or astral rays and so they exhibit anastral division. For them dictyosomes(golgi complex) function as centrioles/
what is kern plasm theory
mitosis occurs due to distrubance in the karyoplasmic index or nucleocytoplasmic ratio.
when karyoplasmic ration is small celll is high due to less cytoplasm and hence nucleus controls better, when cytoplasm area increases the cell needs to divide
how is surface-volume ratio important
when a cell grows, its size also increases. there will be a stage where its volume is greater than surface area and hence cannot absorb the necessary materials and needs to divide.
what are continuous and discontinuous spindle fibres
continouous ( non kinetochore) run from pole to pole
discontinuous/ kinetocore/ chromosomal fibre- run from pole to kinetochore
How does duration of cell division vary from cell to cell
The duration of cell division varies from organism to organism and also from cell type to cell type.
what is colchicine
it is mitotic poision and prevents formation of mitotic spindle.
prevents the splitting of centromere
stops mitosis at metaphase
what is a mitogen
A mitogen is a small bioactive protein or peptide that induces a cell to begin cell division, or enhances the rate of division (mitosis). Mitogenesis is the induction (triggering) of mitosis, typically via a mitogen.
phytohormones like cytokinin, auxin, and gibberellin, animal hormones like insulin and steroids.
