600314299-Cell-Cycle-1.pdf

NOTE: Practice Personal Hygiene Protocols at All Times 1
SHIRLEY ANNE H. LAXAMANA, SST-III
AGUSAN NATIONAL HIGH SCHOOL
SENIOR HIGH SCHOOL
Guide Question: 1. What are the phases of the cell cycle?
Republic of the Philippines
Department of Education
CARAGA ADMINISTRATIVE REGION
DIVISION OF BUTUAN CITY
SENIOR HIGH SCHOOL
GENERAL BIOLOGY 1
Quarter 1, Week 4
Name : _________________________________________________ Date: ________________________________
Teacher : _________________________________________________ Grade & Section: ____________________
Learning Activity Sheet No. 6
THE CELL CYCLE
LEARNING COMPETENCIES:
1. Characterize the phases of the cell cycle and their control points (STEM_BIO11/12-Id-f-6);
2. Describe the stages of mitosis/meiosis (STEM_BIO11/12-Id-f-7)
3. Explain the significance or applications of mitosis/meiosis (STEM_BIO11/12-Id-f-9)
4. Identify disorders and diseases that result from the malfunction of the cell during the cell
cycle (STEM_BIO11/12-Id-f-10)
INTRODUCTION
Living organisms have the ability to produce more of their own kind. Humans give
birth to babies and eventually will turn into a matured human being. A mango seed
which is nurtured with right and good environmental factors will gradually develop into a
tree and will bear mango fruits. Moreover, living organisms have the ability to repair
damaged tissues. That is why when we experience a cut on our skin, it eventually heals
as time goes by. All of these happen because of cell division, the reproduction of cells.
Cell division is a very essential part of the cell cycle, an orderly sequence of events that
takes place in a cell from the time it is first formed from a dividing parent cell to the time
that it will produce its own two daughter cells.
DISCUSSION/CONCEPTS
TWO PHASES OF CELL CYCLE: INTERPHASE and MITOSIS
INTERPHASE
• phase in which the cell prepares itself for
cell division
• divided into subphases:
➢ First Gap Phase (G1 Phase) – cells
undergo a period of growth at a very
fast rate
➢ Synthesis Phase (S Phase) – the DNA is
replicated; each chromosome has two
sister chromatids
➢ Second Gap Phase (G2 Phase) – cell
grows again and completes
preparations for cell division █ Figure 1. Cell Cycle

SENIOR HIGH SCHOOL
D. Telophase
➢ last phase of mitosis
➢ two daughter nuclei are
formed
➢ spindle fibers disappear
➢ nuclear membrane forms
around the
chromosomes
Guide Question:
2. Differentiate
karyokinesis and
cytokinesis.
MITOSIS (M Phase)
• a type of cell division in which a daughter cell has the same number of chromosomes
as the parent cell; also defined as the equational division
• a phase where nuclear division occurs known as karyokineses
• occurs in body cells, for growth and replace worn out cells
Stages of Mitosis
A. Prophase
➢ nucleolus disappears
➢ chromatin condenses to form chromosomes
➢ two identical copies of each chromosome
(sister chromatids)are attached to
centromere
➢ centrosome moves to opposite poles
➢ formation of mitotic spindle
B. Metaphase
➢ chromosomes lined up at the equatorial plate
➢ nuclear membrane completely dissolves
C. Anaphase
➢ replicated chromosomes separate
➢ daughter chromatids move to opposite
poles
➢ chromosomes are very condensed at the
late anaphase
Cytokinesis
➢ division of
cytoplasm
➢ divides the cell
into two daughter
cells which are
identical to the
parent cell
█ Figure 2.1 Prophase
█ Figure 2.2. Metaphase
█ Figure 2.3 Anaphase
█ Figure 2.4 Telophase
█ Figure 2.5 Cytokinesis

SENIOR HIGH SCHOOL
MEIOSIS
• a type of cell division in which a daughter cell has half the number of chromosomes of
the parent cell; also defined as the reductional division
• involved in the formation of sex cells or gametes (sperm and egg cell)
• the number of chromosomes in a gamete is called the haploid chromosome number, or
n; the number of chromosomes in all other cells having a
nucleus is twice the haploid number and is called the
diploid number, or 2n
• a human cell which consists of 46 chromosomes will
undergo meiosis and produce gametes that have 23
chromosomes
• human offspring (zygote which is diploid, 2n=46) is a
combination of genetic information from parents, 23
chromosomes (haploid, n=23) from the father (sperm cell)
and 23 chromosomes (haploid, n=23) from the mother
(egg cell)
• homologous chromosomes are paired chromosomes
which is similar in shape, size, and gene
arrangement
• has two nuclear divisions that produce four haploid cells
• for reproduction of species
STAGES OF MEIOSIS
MEIOSIS I First Division
• diploid chromosome (2n) is reduced to the haploid (n) chromosome number
PHASES
PROPHASE I -the longest subphase of meiosis; has five distinct substages
➢ Leptotene (Condensation) – chromosomes duplicate, condense and coil
➢ Zygotene (Pairing)- chromosomes start to pair up with other chromosomes that carry
the same set of genes in the process called synapsis; the thin space between the
two chromosomes is called
synaptonemal complex; paired
chromosomes are called as
homologous chromosomes and
the whole structure is called tetrad
or bivalent because each pair is
made up of four chromatids
➢ Pachytene (Recombination)- genetic information is exchanged between chromosome
pairs in the process of crossing over which results to the formation of chiasma
(plural: chiasmata) that serves as attachment of two non-sister chromatids
█ Figure 3.1 Homologous Chromosomes
█ Figure 3.2 Pairing of Homologous Chromosomes via Synapsis
█ Figure 3.3 Chiasma

SENIOR HIGH SCHOOL
Guide Questions:
3. Do homologous chromosomes have identical genes? Explain
4. Do homologous chromosomes have the same number of genes? Explain
5. How are haploid cells different from diploid cells?
➢ Diplotene (Coiling) – synapsis ends and the synaptonemal complex disappears;
homologous pairs of chromosomes remain attached at chiasmata
➢ Diakinesis (Recondensation)- chromosomes are fully condensed and nuclear
membrane disappears
METAPHASE I – homologous chromosomes are attached to the spindle fibers and line up
along the equatorial plate
ANAPHASE I – homologous chromosomes separate and move toward the opposite poles;
one member of the homologous pair will be distributed in each new cell
TELOPHASE I – nuclear membrane starts to form around each nucleus; chromosomes in the
two nuclei are not the same because each of the daughter cells contains one
member of the homologous chromosome pair and has half the number of
chromosomes of the parent cell
MEIOSIS II Second Division
• similar to mitosis but genetically unidentical; results in the formation of four haploid cells
from the two haploid cells produced in Meiosis I
• no replication of chromosomes
PHASES
PROPHASE II – signals the start of second meiotic division; nuclear membrane disappears
and spindle fibers gradually form
METAPHASE II – chromatids pinned together by
centromeres with two kinetochores are
attached to the spindle fibers from
centrosomes at opposite poles;
chromosomes aligned at the equatorial
plate.
ANAPHASE II – sister chromatids of each chromosome separate and move to opposite
poles; nuclear membrane starts to form around the chromatids
TELOPHASE II – final stage of meiosis; second division of cytoplasm; four haploid cells
are produced
REMEMBER:
Homologous chromosomes may be similar but they are not identical. They bring genes
for the same traits (e.g. hair color), however those genes differ in codes (e.g. black color
or brown color).
Terms:
centromere- holds two sister chromatids in a
chromosome
kinetochore – disc shaped protein complex found in
centromere region of the chromosome where
spindle fibers are attached
█ Figure 3.4 Centromere and Kinetochore of
Chromosome

SENIOR HIGH SCHOOL
Guide Question:
6. What are the differences of Meiosis I and Meiosis II?
THE CELL CYCLE CONTROL SYSTEM
• a cyclically operating set of molecules in the cell that both triggers and coordinate key
events in the cell cycle; regulated at certain checkpoints by both internal and external
signals
• checkpoints – control points of stop and go-ahead signals in the cell cycle
• three major checkpoints - G1, G2, and M
█ Figure 3.5 Meiotic Division

SENIOR HIGH SCHOOL
Guide Questions:
7. Describe the functions of each checkpoint
in the cell cycle.
8. What happens when an error occurs in the
cell cycle?
G1 Checkpoint
➢ “restriction point”, the most
important checkpoint
➢ if a cell receives go-ahead
signal, it will usually complete
the G1, S, G2 and the M phases
➢ checks for nutrients, growth
factors and DNA damage
➢ if a cell does not receive a go-
ahead signal at this point, it
will exit the cycle, switching
into a nondividing state called
the G0 Phase (e.g. mature
nerve cells and muscle cells
never divide so they stay in this
phase)
G2 Checkpoint
➢ occurs during synthesis phase
➢ assesses proper chromosome duplication; checks if the cell size is suitable for cell
division; if so, the cell continues on to Mitosis
M Checkpoint
➢ occurs during the mitosis phase
➢ checks if attachment of chromosome to spindle is correct
➢ checks whether mitosis is complete
➢ if so, the cell divides and the cycle repeats
MALFUNCTION OF THE CELL DURING CELL CYCLE
Despite of the cell cycle checkpoints; errors will still occur. One of the very critical
processes is the proper duplication of DNA in the synthesis phase. A small mistake will lead
to mutation (replication error). And this gene mutation will be passed to daughter cells which
will lead to uncontrolled growth of mutated genes. This will result to nonfunctional
checkpoints and normal cells will be outnumbered
by rapidly reproducing mutated genes which lead
to carcinogenesis or tumor development. An
example of this is the cancer of the blood,
leukemia, in which the body makes many
abnormal white blood cells. The blood can no
longer do its job.
█ Figure 4.1. Cell Cycle Checkpoints
█ Figure 4.2 G0 Phase
█ Figure 5. Leukemia

SENIOR HIGH SCHOOL
Guide Questions:
9. What are the importance of mitosis and
meiosis?
10. How is meiosis a basis for evolution?
MITOSIS: IMPORTANCE AND APPLICATIONS
• Growth and development of an organism by producing new cells
• Heals and repairs worn out cells and replaces the old and damaged cells with new cells
• Responsible for asexual reproduction where the offspring is a clone to its parent organism
➢ Binary Fission – single-celled organisms like amoeba reproduce by splitting into two
new cells (Figure 6.1)
➢ Budding – organism like yeast reproduce through the bud on a parent organism
which eventually develops into a new organism (Figure 6.2)
➢ Vegetative Reproduction – plants with stolon and rhizome produce new organism
like grasses, ferns, and strawberries (Figure 6.3)
• Hereditary traits are equally distributed to the daughter cells
• Genetic information from parent organism is preserved or remain unchanged from one
generation to another generation
MEIOSIS: IMPORTANCE AND APPLICATIONS
• Production of sex cells or gametes, sperm cell for male, and egg cell for female
➢ Gametogenesis – formation of gametes or sex cells in animals
➢ Spermatogenesis – production of sperm cells (Figure 6.4)
➢ Oogenesis – production of egg cell (Figure 6.4)
• Responsible for sexual reproduction of organisms which carries genetic information from
the father and mother
• Results in the variation of genetic traits among offsprings
• Maintain the number of chromosomes among organisms in each new generation
• Basis for evolution because of the variations produced
█ Figure 6.1
█ Figure 6.2. Budding of Yeast
█ Figure 6.3. Strawberry Reproduction
█ Figure 6.4. Oogenesis and Spermatogenesis

SENIOR HIGH SCHOOL
EXERCISES/ACTIVITIES
Activity 1: COMPARISON OF MITOSIS AND MEIOSIS
A. Direction: Copy the table below on your paper and fill up the columns under mitosis
and meiosis with the correct answer
COMPARISON MITOSIS MEIOSIS
Definition (What kind of division?)
Type of cell involved
Number of nuclear divisions
Number of daughter cells produced
Chromosome number of each daughter cell
(diploid or haploid)
Genetic Variations (Present or Absent)
Type of daughter cells (identical or unidentical)
Homologous chromosomes (Present or Absent)
Type of Reproduction
Crossing Over (Present or Absent)
Chiasmata (Present or Absent)
Function
B. Direction: Identify what phase of mitosis and meiosis does each of the following occurs.
Write your answer on your paper.
Example: Event: Replicated chromosomes (same genetic information) move to the
opposite poles Answer: Anaphase
1. Chromosomes condense with two chromatids attached on a centromere.
2. The last phase of mitosis.
3. Paired chromosomes form a structure with four chromatids.
4. This phase signals the start of the second meiotic division.
5. Chromatids with the same genetic information move to the opposite poles of the cell.
6. The second division of cytoplasm and four haploid cells are developed.
7. Chromosomes with exchanged genetic information line up along the equator.
8. Two daughter nuclei with the same genetic information are produced.
9. Chiasma that serves as attachment of two non-sister chromatids is formed.
10.Two daughter cells with different genetic information are produced.
11. Homologous chromosomes move to the opposite poles of the cell.
12. It is in this phase where crossing over occurs.
13. The final stage of meiosis.
14. Homologous chromosomes are attached to the spindle fibers and line up along the
equatorial plate.
15. The start of synapsis.

SENIOR HIGH SCHOOL
Activity 2: LABELING DIAGRAMS
Direction: Label each diagram below. Write your answer on your paper.
_________
_________________
________________ ____________________
2
5
1
3
4 6.
7.
8.
9.
12.
13.
14.
15.
17. 18. 19. 20.
21. 22.
23.
24.
16. 25.
10.
11
.

SENIOR HIGH SCHOOL
EVALUATION
Direction: Choose the best answer and write the letter of your choice on your paper.
1. The main function of mitosis is for ____________________________________
A. reproduction of species. C. formation of sex cells.
B. growth and development of body cells. D. gene variation.
2. What is the diploid number of human chromosomes?
A. 23 B. 48 C. 22 D. 46
3. Homologous chromosomes are ___________________________________________________
A. paired chromosomes which is similar in shape, size, and gene arrangement.
B. paired chromosomes which are similar and identical.
C. paired chromosomes having the same gene traits and gene codes.
D. paired chromosomes that are not similar and unidentical.
4. The following are the important things to be checked in G1 checkpoint EXCEPT
A. nutrients B. growth factors C. DNA duplication D. DNA damage
5. Which of the following does not describe meiosis?
A. equational division C. diploid parent cell
B. haploid daughter cells D. reductional division
6. What cell cycle control point made it sure that the chromosome is attached to spindle
correctly?
A. G1 checkpoint B. M checkpoint C. G2 checkpoint D. Both A and C
7. In what phase of the cell cycle does nondividing cells is put into place?
A. M phase B. G1 phase C. G0 phase D. G2 phase
8. Which substages of Prophase I does crossing over occur?
A. Pachytene B. Diplotene C. Zygotene D. Leptotene
9. What is the haploid number (n) of chromosomes if dogs have a diploid number (2n) of 78
chromosomes?
A. 156 chromosomes B. 78 chromosomes C. 39 chromosomes D. 19 chromosomes
10. This happens when genetic information is exhanged between homologous chromosomes
A. crossing over B. synapsis C. gametogenesis D. cytokinesis
11. Which of the following is the correct comparison of mitosis and meiosis?
A. Mitosis has two identical daughter cells produced while Meiosis has four identical
daughter cells.
B. Meiosis has one division while Mitosis has two divisions.
C. Mitiosis is a reductional divison while Meiosis is an equational division.
D. None of the above.
12. The thin space between homologouse chromosomes is called as ____________________
A. tetrad B. synaptonemal complex C. chiasma D. synapsis
13. What happens when there is a gene mutation in the cell?
A. rapid growth of cells with mutated gene
B. cannot stop uncontrolled growth of mutated genes
C. nonfunctional checkpoints in the cell cycle
D. all of the above
14. Which of the following undergoes sexual reproduction?
A. fertilization B. binary fission C. budding D. vegetative reproduction
15. Leukemia is a type of cancer which affects the _____________________
A. kidney B. heart C. blood D. brain

SENIOR HIGH SCHOOL
REFLECTION
Write what you have learned from this activity.
_______________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
__________________________________________________________________________________________
REFERENCES
Aven.amritalearning.com. (2013). Asexual Reproduction in Plants. [Digital Image]. aven.amritalearning
.com/index.php?sub=100&brch=293&sim=1485&cnt=3423
Biologydictionary.net. (n.d.). Phases of Meiosis. [Digital Image]. https://biologydictionary.net/meiosis/
Cornell, B. (2016). Pairing of Homologous Chromosomes. [Digital Images]. https://ib.bioninja.com.au/
higher-level/topic-10-genetics-and-evolu/101-meiosis/chiasmata.html
Cornell, B. (2016). Cell Checkpoints. [Digital Images]. https://ib.bioninja.com.au/higher-level/topic-10-
genetics-and-evolu/101-meiosis/chiasmata.html
Emedicalprep (2019). Cell Cycle and Cell Division. [Digital Images]. https://www.emedicalprep.com/
study-material/biology/cell-structure-functions/cell-cycle-cell-division/
Openstax College, (2013, November). Biology.Openstax CNX.https://cnx.org/contents/ GFyh8cu@
14.1:1tJ55Ot6@9/10-2-The-Cell-Cycle
Pearson Education (n.d.) Homologous Chromosomes. [Digital Image]. http://www.phschool.com/
science/biology place/labbench/lab3/homologs.html
Proprofs.com (n.d.). Cell Biology-The Cell and its Environment. [Digital Image]. https://www.proprofs.
com/quiz-school/story.php?title=cell-biology-the-its-environment
Reece, Jane B., et al. (2011). Campbell Biology (9th Edition). SanFrancisco, United States: Benjamin-
Cummings Publishing Co.
SaintLuke (n.d.). What is Leukemia?.[Digital Image} https://www.saintlukeskc.org/health-library/what-
leukemia
Sastry, (2018, September). Binary Fission in Amoeba. [Digital Image]. https://www.aplustopper.com/
different-types-asexual-reproduction/
Shutterstock.com. (n.d.). Strawberry Reproduction. [Digital Image]. https://www.shutterstock.com/
search/strawberry+reproduction
Steemit.com. (n.d.). Meiosis. [Digital Image]. https://steemit.com/meiosis-in/@marza/meiosis
Prepared by:
SHIRLEY ANNE H. LAXAMANA
SST-III

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