Parent and Daughters.
-New daughter cells form from parent cells in a series of events called the CELL CYCLE.
-The daughter cells produced must be able to CARRY OUT the SAME FUNCTION as the parent cell.
Chromosomes- The instructions.
-Chromosomes are in the NUCLEUS of EUKARYOTIC cells.
-Each chromosomes witholds one molecule of DNA which includes specific lengths of DNA called GENES.
-Therefore, the chromosomes contain vital INSTRUCTIONS for making new cells.
-The daughter cell must contain an EXACT COPY of all these instructions (a full set of chromosomes).
-Human's have 46 chromosomes.
Copying and Separating.
-In EUKARYOTES the DNA that make up the chromosomes are WRAPPED around PROTEINS called HISTONES.
-The DNA + HISTONES= CHROMATIN.
-Before a cell can divide to produce two new daughter cells the DNA of each chromosome needs to be REPLICATED...TWO REPLICATES are produced.
-These replicates are the exact same as the original and are held together at a point called the CENTROMERE. = INTERPHASE
Copying and Separating part 2.
-At this stage you are UNABLE to see the chromosomes under a LIGHT MICROSCOPE.
-Now each chromosome consists of TWO DNA REPLICA STRANDS= SISTER CHROMATIDS.
-Next the sister chromatids must be SUPERCOILED to form VISIBLE chromosomes.
-Now they can take up stains and be seen under a light microscope.
-Before being supercoiled they are around 30nm thick and after they are around 500nm thick.
-They can't perform their normal functions in this state so the length of time they are in a supercoiled state needs to be as short as possible.
Checks and Balances.
-As the DNA is being replicated PROOF-READING ENZYMES move along the new DNA strands and check the copying has been done properly.
-If there is a fault in the copying= a mutation= the new cell may fail to function.
Cell Cycle- Length of time.
-The length of time taken for a parent cell to divide into two daughter cells, and for each to grow to full size, varies between species and cell type.
-It also is affected by the availability of nutrients for the cells.
-Mitosis occupies only a small proportion of the cell cycle and the remaining larger potion includes COPYING, CHECKING GENETIC INFORMATION of the DNA and PROCESSES ASSOCIATED with GROWTH.