LECTURE SUMMARY 5 and 6
The cycle of cell growth
A complete set of genetic instructions
Produce required molecules• direct life processes
Genetic instructions are coded in the DNA of cells
The entire mechanism of prokaryotic cell division is called binary fission and
can be broken down into three periods.
B period- DNA Synthesis
C period- chromosomes are replicated and move to separate ends of the cell
D period- membrane pinches together between them and two daughter cells
Eukaryotic chromosomes contain a much greater length of DNA than
Interphase-cell grows and replicates DNA in anticipation of cell division
(g1 phase- cell makes various RNA’s proteins and other types of cellular
(s phase- the cell duplicates chromosomal proteins as well as DNA)
(g2 phase- cell continues to grow, cell continues to make RNA and proteins)
After interphase the cell begins the process of mitosis which can be broken
down into 4 stages:
Prophase-chromosomes condense into compact rodlike structures. Mitotic
spindles begin to form between two centrosomes as they start migrating
towards opposite ends of the cell to form Cell Poles.
(prometaphase- the nuclear envelope breaks down initiating prometaphase.
Spindles are sent from the centrosomes at opposite ends of the cell, some
spindle may attach to chromosomes.
Metaphase- spindle microtubles move the chromosomes into alignment at
the spindle midpoint, also called the metaphase plate.
Anaphase- the spindles separate the two sister chromatids of each
chromosome and move them to opposite ends of the cell.
Telophase- the spindles detach and chromosomes unfold and return to the
interphase state, and new nuclear envelopes form around the daughter
nuclei. The cytoplasm is beginning to divide at the cleavage point.
Cytokenesis is the process of splitting the daughter cells apart.
Regulation of the cell cycle is crucial in order to develop normal.
G1- restriction point- most important point, if the cell receives the go ahead
at this point it ill complete the cell cycle and divide but if it does not it will
enter a non dividing state called the G0 phase. This is when specialized cells
stop reproduction to perform specialized functions. Ex nerve cells. MEIOSIS
Haploid aka 1n is when cells have one complete set of chromosomes (ex
sperm cells or unfertilized eggs)