4. cell cycle and mitosis Flashcards
why does DNA replication occur
All cells need DNA to be able to make proteins.
When a cell (the parent cell) divides into two daughter cells, each daughter cell must inherit the full set of DNA from the parent cell.
If this wasn’t the case, the daughter cells wouldn’t be able to make all the necessary proteins for their survival.
DNA helicase function
-unzips double helix
-breaks relatively weak H bonds between complementary base pairs
RNA primase function
adds an RNA primer to the 3’ end of the leading strand that allows DNA polymerase to begin to synthesize a new DNA strand complementary and specific to the template strand
DNA polymerase
begins to synthesise a new DNA strand that is complementary and specific to the template strand by joining free nucleotides via complementary base pairing
DNA ligase function
Joins Okazaki fragments by their sugar phosphate backbone on the lagging strand
Chromosome
Thread like structure composed of DNA and associated proteins (histones) containing many genes at specific loci
5 steps in binary fission
- DNA replication
2.Elongation - Septum formation
- Cytokinesis
what happens in elongation
cytoplasmic membrane elongates separating DNA molecules
what happens in septum formation
cross wall begins to form.
membrane invaginates.
what is an RNA primer and what is its function
An RNA Primer is a short sequence of RNA nucleotides (5~10 nucleotides long) that is complementary to the template strand.
It provides an attachment site for DNA polymerase.
what happens during G1
Cell growth, Production of enzymes involved in DNA replication, Normal cellular functions.
what happens in G2
Cell growth/ Normal cellular functions/ Preparation for mitosis (producing proteins involved in mitosis).
what happens in prophase
DNA condense into chromosomes and become visible.
Nuclear membrane disappears.
Centrosomes migrate to two opposite poles of the cell.
what happens in metaphase
Chromosomes align along the equator of the cell.
Spindle fibres attach to the centromeres of the chromosomes.
what happens in anaphase
Sister chromatids pulled apart to opposite poles of the cell by spindle fibres.