Cell division, cell diversity and cellular organisation Flashcards
mitosis occupies only a small percentage of the cell cycle and the remaining percentage includes the copying and checking of genetic information
mitosis occupies only a small percentage of the cell cycle and the remaining percentage includes the copying and checking of genetic information
interphase
the dna replicates
prophase
the chromosomes supercoil and become visible under the light microscope
nuclear envelope breaks down
the centriole divides in two and moves to opposite ends of the cell to form a spindle
metaphase
the chromosomes line up along the middle of the cell
they attach to the spindle thread at their centromere
anapahse
the replicated sister chromatids are separated when the centromere splits
the spindle fibres shorten, pulling the chromatids apart
telophase
as the separated sister chromatids reach the poles of the cells
a new nuclear envelope forms around each set
the spindle breaks down
the chromosomes uncoil so they are no longer visible under a light microscope
cytokinesis
the whole cell splits down to two new cells, each one identical to each other and to the parent cell
explain the meaning of homologous pair of chromosomes
chrosnomes that have the same genes at the same loci. members of a homologous pair of chromosomes pair up in meiosis. diploid organisms produced by sexual reproduction have homologous pairs of chromes- one member of each pair from the mother and one from the father
explain the significance of mitosis for growth, repair and asexual reproduction in plants and animals
growth- multicellular organisms produce new extra cells to grow - each new one being genetically identical to the parent cell-and so can perform the same function
repair- damaged cells need to be replaced by new ones that perform the same function
asexual reproduction- single celled organisms divide to produce two daughter cells that are separate organisms
some multicellular organisms produce offspring from parts of the parent.
outline budding process in yeast cells
yeast undergo cytokinesis- by producing a small bud at the cell membrane that pinches off.
define the term stem cell
undifferentiated cells that ARE capable of becoming differentiated into a number of different cell types
differentiation in plant cells - the production of xylem vessels and phloem sieve tubes from cambium.
xylem and phloem both come from meristem cells.
in xylem the meristem elongate- the walls becoming elongated and waterproofed by deposits of lignin, which kills the cell contents. the ends of the cells breakdown so they become long tubes with wide lumen. they are suited to transporting water and mineral up the plant
