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MITOSIS

1.

Cell Cycle

Name and state the purpose of each of these sub phases

P1 : G 1 The cells builds up a large store of energy and synthesises cytoplasmic organelles such as mitochondria and ribosomes.

Q : S Replication of DNA P2 : G2 The cell accumulates energy and completes its final preparations R : Mitosis Process of nuclear division. S : Cytokinesis Process of division of the cytoplasm into two daughter cells.

2. State the definition of Mitosis.

P P

Q

R S

MITOSIS Process by which a nucleus divides to produce two daughter cells, each containing the same number of chromosomes as the parental cells.

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3. Rearrange the jumbled words . The importances of mitosis are:

a. W O T H G R Growth b. ELLC E C A L P N E T E R M Cell replacement c. G E T O I R E N E N A Regeneration d. X E S A A U L D U T C I N E R R O P Asexual reproduction

4. Label the diagram below.

5. Underline the correct words in the bracket.

Cytokinesis is occurs ( just prior to , after ) mitosis. Between divisions, cells are in ( dormant-phase , interphase ) , an active period during which chromosomal DNA is duplicated, the cell mass ( increases, decreases) and new organelles are produced. Nuclear DNA is replicated only during ( G1 , G2 , S ) phase. The process of mitosis occurs in the following order : prophase, ( anaphase , metaphase ) , ( anaphase , metaphase ) and telophase. The mitotic spindle is a complex of ( microtubules , microfilaments ) that ( prevents , assists ) chromosomes movement. The spindle is attached to each chromosome at a site called the ( connector , centromere ). Following nuclear division, the cytoplasm of the cells is divided. The soon-to-be daughter cells are

separated by the cleavage ( plane , furrow ) in animals cells and the cell ( plate , furrow ) in the plant cells.

i. Sister Chromatid

ii. Centromere

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6. How does mitosis in plant cells differ from mitosis in animal cells ?

Cell division in plant and animal cells differs in two ways : (1) animal cells have centrioles , whereas plants cells do not , and (2) animal cells have cleavage furrows , whereas plant cells have cell plates .

8. Complete the flow chart below

Tissue Culture Technique

Root of carrot

Transverse section of root

Cell ( 2 n )

Fragments cultured in nutrient medium

Cell division mitosis to form Callus

Cultured on agar medium and transferred to soil

Adult plant

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9. Explain briefly how Dolly the sheep was produced by cloning. Give your answer in the form of a flow chart which shows the successive steps with explanatory notes for each step.

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10. ADVANTAGES AND DISADVANTAGES OF CLONING

Advantage Disadvantage Cloned plant are uniform is size and shape Clones are susceptible to new diseases Plants can be produced all the year Clones are easily destroyed if there is a

change in the environment Plant maintain the same designed characteristics of the mother plants Tissue culture techniques are cost effective Clones can be produced in vast numbers in a short time

MEIOSIS

11.

MEIOSIS Process by which a nucleus divides to produce four daughter cells, each containing half the number of chromosomes of the parental cell.

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12. Fill in the blank using the words provided.

1. At metaphase II phase of meiosis are these two cells, each with sister chromatids aligned at the spindle equator.

2. The meiotic process by which homologues are paired during prophase I is called Synapsis .

3. Crossing occurs during Prophase I 4. Meiosis consists of two nuclear divisions, producing four haploid cells. 5. The function of meiosis I is to separate Homologous chromosomes . The

function of meiosis II is to separate Sister Chromatids . 6. Meiosis I produces two Haploid cells. 7. Meiosis II produces four Haploid cells.

13. By using two different colours show the result of crossing-over.

Synapsis Sister Chromatids Metaphase II four

Haploid Haploid Homologous chromosomes

Two Diploid Prophase I Diploid

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14. Complete the table below.

15. Name the stages in the diagrams above.

Name of Phase Description

1. Prophase I Homologous chromosomes pair up and form tetrad

2. Anaphase I Spindle fibers move homologous chromosomes to opposite sides

3. Telophase II Nuclear membrane reforms, cytoplasm divides, 4 daughter cells formed

4. Metaphase II Chromosomes line up along equator, not in homologous pairs

5. Prophase I Crossing-over occurs

6. Anaphase II Sister chromatids separate

7.Metaphase I Homologous chromosomes line up alone equator

8. Telophase I Cytoplasm divides, 2 daughter cells are formed

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Answers :

1. Anaphase I 2. Anaphase II 3. Prophase I 4. Metaphase I 5. Metaphase II 6. Telophase I 7. Metaphase II 8. Telophase II

16. If a diploid cell has two chromosomes ( 2n = 4 ) , Draw and describe the events that occur in each stage in mitosis and meiosis.

Mitosis Prophase

Meiosis I Prophase

Meiosis II Prophase

Chromosome behaviour

o Chromosomes in the condense and become tightly coiled.

o Pair of sister chromatids joined together at the centromere.

o The chromatin begins to condense

o Homologous chromosomes pair up by a process called synapsis

o Crossing-over occurs

o Each of the two haploid daughter cells from meiosis I undergoes chromatin coiling to form chromosomes, each of which is composed of 2 chromatin.

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Mitosis Metaphase

Meiosis I Metaphase

Meiosis II Metaphase

Chromosome behaviour

o Centromeres of all the chromosomes are lined up on the metaphase plate

o The bivalent arrange themselves at the equator of the spindle.

o Centromeres of chromosomes become attached to individual spindle fibres.

o Chromosomes attach to the spindle fibers at the centromeres

and move to the equator of the cell.

Mitosis Anaphase

Meiosis I Anaphase

Meiosis II Anaphase

Chromosome behaviour

o Two sister chromatids of each chromosomes separate at the centromere.

o The sister chromatids are pulled apart to the opposite poles.

o Homologous chromosomes separate. One of the pairs is pulled to one pole and the other to the opposite pole.

o Centromeres allowing the chromatids to separate toward the poles

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Mitosis Telophase

Meiosis I Telophase

Meiosis II Telophase

Chromosome behaviour

o Chromosomes reach opposite poles of spindle.

o The chromosomes start to uncoil and revert to their extended state.

o Chromosomes reach opposite poles of spindle.

o Four haploid cells are formed.

o The chromosomes unwind and change from chromosomes to chromatin

17. COMPARE AND CONTRAST

1. Complete the table below. Meiosis I Similarities Meiosis II

1. The chromosomes become condense and shorter during prophase. 2. The chromosomes are arranged at the metaphase plate.

MEIOSIS I Aspect compared MEIOSIS II Homologous chromosomes pair up and crossing over between non-sister chromatids occurs.

Prophase Synapsis of homologous chromosomes and crossing over between non- sister chromatids does not take place

Homologous chromosomes align at the metaphase plate of the cell

Metaphase Chromatids align at the metaphase plate ( equator) of the cell

Homologous chromosomes separate and move to opposite poles. Sister chromatids are still attached together and move as

Anaphase Sister chromatids separate becoming daughter chromosomes that move to opposite

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a unit. poles. Two haploid daughter cells are formed.

Telophase Four haploid daughters are formed.

Each daughter cell has only one of each type of chromosome : either the paternal or the maternal chromosome.

Each daughter cell has the same number of chromosome as the haploid cell produced in meiosis I but each cell has only one if the sister chromatids.

18. Complete the table below.

Mitosis Similarities Meiosis 1. A nuclear division process 2. Nuclear division occur

MITOSIS Aspect compared MEIOSIS Somatic cells Place occur Gonadic cells Produce cells for growth and tissue repair

Role Produce gametes

Once Number of sitokinesis Twice Does not occur Synapsis of

homologous chromosomes

Occurs during prophase I

Two Number of daughter cells

Four

Diploid ( 2n ) Set of chromosomes Haploid ( n) Identical to the parent cell Genetic composition of

daughter cells Non_identical to the parent cell and to each other

No variation produced Variation Produces genetic variation

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EXERCISES

1. Diagram 1.1 shows phases M and N during meiosis I.

M phase : Anaphase I N phase : Metaphase I Description : The homologous chromosomes are pulled apart to the opposite poles

Description : The homologous chromosomes arrange themselves at the equator of the spindle.

a. In the space provided,

i. State the both stages in M and N

ii. Describe the behaviour of both chromosomes in above stages.

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b. Diagram 1.2 shows the chromosome behaviour during Prophase I in meiosis.

i. State the M process Crossing-over

ii. State the part of chromatids where the M process occurs. Chiasmata

c. Based on diagram 1.2, draw the chromosome behaviour during Prophase II.

M

OR

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d. Based on the above statement, explain how the situation happens.

F1 : Parents have different of gametes . F2 : Meiosis produced different of genetic mass in the gametes.

F3 : It occur when homologous chromosomes randomly arrange in Meiosis I / Crossing-over in Meiosis I

F4 : Fertilization / combination of gametes in randomly

e. Diagram 1.3 shows the formation of cancer cell in epithelium.

Based on diagram 1.3 , explain how the cancer happens.

F1 : Normal cells absorbed UV rays F2 : Uncontrolled mitosis // Increasing of cell rate greatly // change of cell form

Statement :

Meiosis is a process to produce gametes that take place in sex organ.

Case :

In a family, there are variability occurs in offspring.

Epithelium cells Cancerous cells

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2. Meiosis is involved in the production of gametes for sexual reproduction. Offspring produced by sexual reproduction differ genetically from one another and from the parents. Draw a diagram and explain briefly how meiosis makes genetic variation possible.

3. Diagram shows the differences that occur in a family member.

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Based on diagram 8, identify the differences among the family members. Discuss how the differences are inherited.

Example : Father has curly hair. Mother has straight hair Daughter has curly hair.

Ei : Gametogenesis is the production of gametes in the gonads Eii : o Crossing-over/exchange of genetic material during meiosis I between

pairs of homologous chromosomes. o Arrangement of homologous chromosomes during metaphase I occurs

randomly o Total number of haploid chromosomes Eiii : o Fertilisation between gametes occurs randomly o The number of combination between the ovum and any one sperm is very

great Eiv : Recombinations of chromosomes resulting in the production of an offspring with various characteristics Ev : Offsprings display phenotypes based on dominant alleles.

4. Diagram 2.1 shows phase X and phase Y in the cell cycle of an organism. Phase X consists of three sub-phases, P, Q and R. Phase Y involves two processes, U and Y.

Diagram 2.1

(a) (i) Name process U. Mitosis

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(ii) State two roles of process U in an organism.

Replacing dead cells Damaged tissues to be repaired Increase the number of cells/ Growth development Asexually reproduction

[ any two ]

(b) Diagram 2.2 shows the various stages in process U.

Diagram 2.2

(i) Based on Diagram 2.2 complete the correct sequence of stages in process U.

Stage Stage Stage Stage IV II III I

(ii) Name the stages in process U.

Stage

Name of stage

I Telophase

II Metaphase

III Anaphase

IV Prophase

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(c) (i) Name phase X in Diagram 2.1. Interphase

(ii) Describe what happens in the cell during phase X. Chromatin undergoes replication Enzyme and protein are synthesised Cytoplasm and number of organelles increase

(d) A technique which involves the cell cycle shown in Diagram 2.1 could used in cattle farming. A researcher use the technique to increase the number of beef cattle. Describe the technique.

Cell from the cattle is chose. Nucleus is transferred from a somatic cell. To an ovum / embryonic cell with the nucleus removed The somatic nucleus transferred to ovum The cells divides repeatedly, forming an embryo The embryo is then implanted into a surrogate mother.

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