Name: Rosnitah bt Yacob

No.metric: D20091035118

REFlECTION: HOW CELL REPRODUCES.

All my body part are begin with cell division. In this topic, there are many interesting
topic that i can learn. Many organisms begin life as a single cell, a zygote, that is formed from
the fertilisation of an ovum by a sperm. Myself also is come from the fertilisation of my
fathers sperm and my mothers ovum. In multicellular organisms, countless division of the
original fertilised eggs will then take place to build up the organism to a higher level of
cellular organisation. As growth take place, many cells undergo fertilisation and modification
to enable them to perform specialised function. For examples, the red blood cell undergo cell
division for carried the oxygen gas for the respiration process. New cell originate only from
other living cells. The dividing cell is named mother cell and its descendants is called
daugther cell. The mother cell transmit identical copies of its genetic information or DNA to its
daughter cell, the next cell generation. For heredity information to be transmitted from
generation to the generation, DNA must be duplicated before the cell divides to provide each
daughter cell a complete copy of the hereditary instructions. This process of cell division is
complicated process and the events in it are divides into two stages which are karyokinesis
and cytokinesis. During karyokinesis, the nucleus and its contents divide to form two nuclei.
The cells cytoplasm and the new nuclei are then partitioned into separate daughter during
cytokinesis.
From my reading and also from lecture delivered by Dr. Shakinaz, most cells divide
one or more times during their lifetime. When they do, they undergo a sequences of stages
that collectively form the cell cycle. The lives of cells is vary, depending on their specific type
and their environments. For example, blood cell and epithelial cell are replaced frequently, so
the cells that produce them undergo frequent cell division. Other cells, such as most nerves
cells, undergoes cell division infrequently or not at all. A cell cycle is a series of events from

one cell division to the next. Its start when a new daughter cell forms by mitosis and
cytoplasmic division. There are many step involve in this cycle which are mitosis, cytoplasmic
division, and interphase. For most cells, interphase is the longest phase. This is because this
phase is the phase where the cells are growth.
For the first stages in cell division which is interphase, it consist of three stages which
are G1, S and G2 phase. I love to learn how the cell change from one cell to another from
this phases because G1, S and G2 phase have different patterns of biosynthesis. In this
subtopic, i learn a lot of things about intherphase where a time for growth and making new
cellular part, replicating DNA and centrioles, and producing the protein, RNA, and organelles
needed for cell division. This phases During the G1 phase, cells growth, poduce new
organelles, carry out specific metabolic activities, and produce protein required for cell
division. Protein are so important in order to do whatever activity in our body. If there are no
proteins or some mistakes happen when the protein are produce, the activities in our body
will not funtionally well. During this phase also, the chromosomes are in their extended form,
and their genes actively directs the synthesis of RNA. Near the end of G1 phase, the
centrioles begin to replicated in preparation for cell division. S phase or synthesis phase is
the next period of interphase for cell that will eventually be dividing. During this short phase,
replication of DNA occur. Can you imagine how the DNA are replicated? For me, it is one of
the miracle process that occur in my body part because the duplication process will copy all
the genetic material consist in the parent strand. The first step in replication is the separation
of the two strands of DNA in the parent molecule. Once separated, each parent strand
serves as a template to determine the order of bases in the new complimentary strand
according to the base pairing pattern. The last part of interphase is G2 phase. During this
phase, synthesis of RNA and protein continues while synthesis of DNA stops. The chromatin
condenses to form short, thick, rodlike structure by the end of G2 phase. Chromosomes
appears double stranded and each strand called chromatin. The DNA are joined together by
a structure know as centromere.

All the subtopic are so interesting for me to know but the most likely for me is the
mitosis process. This is because the mitosis process are the easier topic and easy for me to
remember their stages compare to the others topic in biology. This topic are also represented
by group 1 in showtime session. Based from the presentation and also from my reading, i
have learn that, the entire cell division stages, including both mitosis and cytokinesis is the
termed the mitotic phase. Mitosis is the process by which two daughter cell are produces that
are idntical to the original cell. Four consecutive phases take places during mitosis which are
prophase, metaphase, anaphase and telophase.
Cytokinesis usually begins before telophase ends. Prophase is the first stages in mitosis.
During prophase, the nucleolus breaks down and disappeard. Chromatin becomes
supercoiled into relatively short, dense chromosomes. A duplicated chromosomes consist of
two genetically identical structure called sister chromatids. Each sister chromatid is
composed of an identical DNA double helix, and the two sister chromatid are joined together
by protein called centomere. Elongated microtubules called spindle fibre begin to grow from
the centrioles and this pushes the two centrioles apart. Next is the metaphase phase. This is
the longest stages of mitosis. Prometaphase begins with the dissolution of the nuclear
envelope, which permits the chromosome to move freely into and through the cytoplasm.
Formation of the spindle is the complete and the centrioles move to the opposite pole of the
cell. The collection of spindle fibres extending from the centrioles from the centrioles to the
chromosomes form an oval-structure array termed the mitotic spindle. Metaphase occur
when the chromosomes line up along the metaphase plate. Next is the anaphase phase. It is
the shortest stages of mitosis. Anaphase begin as the spindle fibre pull sister chromatid apart
at the centromere. A pair of single stranded chromosomes is pull apart from the sister
chromatid, and each migrate to the opposite pole of the cell. As each single-stranded
chromosomes migrates toward the cell pole, its centromere leads the way, and the arms of
the chromosomes trail behind. Last but not least, is the telophase phase. Telophase begins
with the arrival of a group of single-stranded chromosomes at each pole of the cell. A nuclear

envelope forms around each set of chromosomes, and the chromosomes begin to uncoil and
return to the form of dispersed threads of chromatin. The mitotic spindle breaks up and
dissappears. Nucleoli reforms and reappears. Telophase signals the end of mitosis and it
may overlap with cytokinesis, the division of the cytoplasm.
Last subtopic in this topic is cytokinesis process. It is also called cleavage. It usually
begins before nuclear division is complete, at the later stages of telophase. In animal cell,
cytokinesis takes places by the formation of cleavage furrow. A contractile ring of
microfilaments at the periphery of the cell equator pinches the mother cell into two separated
cells. The resulting cleavage furrow that appears indicates where the cytoplasm is dividing.
Complete separation of the cytoplasm result in the formation of two daughter cells. For the
plant cell, their unique cell wall is far rigid to be squueezed in two by microfilaments.
Secretion of vesicles containing pectin are carried out by nearby Golgi apparatus. These
vesicles accumulates in the centre of the cell, and fuses together to form cell plate. The
released pectin forms the middle lamella between the new cell and the fused vesicle
membrane form the plasma membrane of each of the cell. This membrane partition, called
cell plate, begin to expand and continues to grow outward until it reach the interior surface of
the plasma membrane and fuses with it, effectively dividing the cell into two. Cellulose is then
laid down on the new membrane, creating two new cell walls.
After the presentation from group 1, we have to do short quiz prepared by Dr.
Shakinaz. This is the good way in order to know whether i really understand about the
mitosis process. Based from this quiz i have got 9 over 10 correct question. Honestly, im
dissapponted with marks that i get because mitosis is one of my favorite topic compare to the
other but for the next test or quiz, i will try to do my best. Inshaallah... Overall, i enjoyed to
learn mitosis because there are many fun activities prepared by lecture in order to make me
really understand about the concept of mitosis.