Cell Cycle And Cell Division Flashcards
What are the three stages The cell cycle is split into?
Inter phase
nuclear division
Cell division
Three stages of interphase
G1 = cell increases in size and volume and new bio mass is made
S =. DNA replicate by semiconservative replication
G2 = cell prepares for division by synthesis and store of ATP a new organelle synthesis
Chromosome
DNA associated with his stones it looks like two identical sister chromatids joined by its centromere and it’s when DNA has been coiled and condensed in prophase
Homologous chromosomes
have the same genes in the same loci but may have different alleles. One chromosome is maternal and the other is paternal.
Three reasons for mitosis
Increasing cell numbers and growth of an organism
Repair of damaged tissue
Replacement of worn out or dead cells
Prophase (4)
nuclear membrane breaks down. Centrioles start to move to the poles of the cell and make spindle fibres. Chromosome supercoil condensed and become visible. Each chromosome appears to identical system chromatids joined at the centromere.
Metaphase(3)
central complete production of spindle fibres. Chromosomes are attached to the spindle fibres by their centromere. The chromosomes aligned down the equator of the cell.
Anaphase (3)
spindle fibres contract and shorten. Centromere splits. Identical sister chromatids are pulled apart to opposite poles making a V shape.
Telophase (2)
nuclear membrane starts to reform around each set of chromosomes. Chromosomes unwind and uncoil and become invisible
Allele
different versions of the same gene
Gene
Sequence
Haploid
cells that contain only a single copy of each chromosome
Diploid
cells which the nucleus contains two sets of homologous chromosome
Somatic cell=
normal body cell
Binary fission
Replication of circular DNA
Replication of plasmids
Division of cytoplasm producing 2 daughter cells
Meiosis 1
P1 and M1 = chromosome super coil and condense and become visible. Homologous prayer of chromosomes power up forming a bivalent and a line across the equator spindle fibres attached to the centromere and crossing over an independent segregation occur here
A1= spindle fibres contract and separate homologous pair of chromosomes pulling each pair to opposite poles of cell
T1= nuclear membrane reforms around separated homologous chromosome
Meiosis 2
P2= each daughter are now has one chromosome from each homologous pair
M2= each chromosome aligns across the equator
A2 = non-sister chromatids are split by the centre and pulled to opposite poles of cell
Nuclear membrane reforms
O
Crossing over
Happens during P1 and M1 of meiosis one
Homologous chromosomes associate forming a bivalent
Chiamata forms where they entangle
Equivalent of of chromatids are exchanged
Producing new combination of alleles
Independent segregation
During metaphase one the homologous chromosomes attached to the spinal fibres and they pair rope side by side and can be reused into any combination
Mitotic index
Number of cell visible / total number of cells
How to make sure mitotic index is accurate
Examine large number of cells / greater field of view = to ensure representative sample
Reapeat count to ensure figures are correct
Only count whole cells to standardise counting
Describe how you would determine a reliable mitotic index on tissue observed with an optical microscope?
Count whole cells in mitosis in field of view
Divide this total number of cells in field of view
Repeat at least 5 times
