Cell Division:

 

1. Cytokinesis is the division of:

(a) Cell

(b) Cytoplasm

(c) Cell wall

(d) Nucleus

 

2. Karyokinesis is the division of:

(a) Cytoplasm

(b) Nucleus

(c) Celiwall

(d) Pollen grains

 

3. Cell division occurring in somatic cells is:

(a) Mitosis

(b) Meiosis

(c) Diplotene

(d) Diakinesis

 

4. In meiotic cell division four daughter cells are produced by two successive divisions in

which:

(a) First division is equational and second is reductional

(b) First division is reductional and second is equational

(c) Both divisions are reductional

(d) Both divisions are equational.

 

5. Duplication of DNA occurs in:

(a) G1-phase

(b) G2-phase

(c) S-phase

(d) M-phase

 

6. The nuclear membrane disappears in:

(a) Prophase

(b) Anaphase

(c) Zygotene

(d) Pachytene

 

7. How many chromosomes are found in a cell of human?

(a) 20 Pairs

(b) 46

(c) 23

(d) 46 Pairs

 

 

 

8. The nuclear membrane and nucleolus become indistinguishable during:

(a) Telophase

(b) Metaphase

(c) Prophase

(d) Interphase

 

9. The disappearance of spindle and uncoiling of chromosomes takes place in:

(a) Anaphase

(b) Telophase

(c) Pachytene

(d) Meiosis

 

10. The regions where crossing-over takes place are called:

(a) Chiasmata

(b) Cell plate

(c) Spindle fibres

(d) Chromosomes

 

11. Duplicated chromosomes are joined at a point termed:

(a) Centrosome

(b) Centromere

(c) Centriole

(d) Chromatid

 

12. The œntromeredivides into two in:

(a) Prophase

(b) Metaphase

(c) Anaphase

(d) Telophase

 

13. After mitotic cell division, a female human cell will have:

(a) yy + xx chromosome

(b) yy + xy chromosome

(c) 22 + x chromosome

(d) 22 + y chromosome

 

14. The period between two successive mitotic divisions is:

(a) Diakinesis

(b) Interphase

(c) Anaphase

(d) Mitosis

 

15. The term meiosis was coined by:

(a) Farmer and Moore

(b) Winiwarter

(c) Flemming

(d) Strasburger

16. Meiosis is also known as:

(a) Equational division

(b) Reductional division

(c) Direct cell division

(d) All of the above

 

17. Meiosis occurs in:

(a) Vegetative cells

(b) Reproductive cells

(c) Meristematic cells

(d) None of the above

 

18. The process of meiosis takes place to produce:

(a) Cells of the body

(b) Cells of the brain

(c) Sperms and ova

(d) Testis and ovary

 

19. Leptotene, Zygotene and Diplotene phases are found in:

(a) Mitosis

(b) Prophase of Meiosis-I

(c) Interphase

(d) Prophase of Meiosis-U

 

Genetics

 

1. Genetics is a branch of biology dealing with:

(a) Heredity in living beings

(b) Variation in living beings

(c) Both heredity and variation

(d) None of these

 

2. Who among the following is called father of genetics?

(a) Mendel

(b) Darwin

(c) Watson and Crick

(d) Lamarck

 

3. When an individual has both tle genes of a contrasting character, it is said to be:

(a) Homozygous

(b) Heterozygous

(c) Phenotype

 (d) Genotype

 

 

 

4. When two individuals differing in at least one character are crossed, the process is

known as:

(a) Hybridization

 (b) Selection

(c) Pedigree

(d) None of these

 

5. A cross was made between tall and dwarf plants. In F1 generation all plants were tall,

when the F1 plants were selfed, the tall and dwarf plants appeared in 3: 1 ratio in F2

generation. This phenomenon is known as:

(a) Dominance

(b) Segregation

(c) Hybridization

 (d) Crossing over

 

6. What is the effect of sexual reproduction?

(a) Offspring is weak

(b) Offspring is like the parents

(c) Offspring is more vigorous

(d) Offspring is diseased

 

7. DNA structure was discovered by:

(a) Lamarck

(b) Mendel

(c) Watson and Crick

 (d) H. G. Khurana

 

8. Chromosomal aberrations are caused by:

(a) Change in the structure of gene.

(b) Change in the number of chromosome.

(c) Change in the arrangement or position of genes.

(d) Change in the number or arrangement of genes in the chromosome.

 

IMPORTANT QUESTIONS:

 

What type of cell division does occur in somatic cells of the body ?

Answer: The mitotic cell division occurs in somatic cells of the body.

 

Where does the meiosis occur in our body ?

Answer: In our body meiosis occurs in germ cells i.e. in gonads.

 

Name the structure which initiates cell division ?

Answer: Centriole (Centrosome).

 

Mention three significant changes that occur in a cell during interphase.

Answer: The three significant changes that occur in a cell during interphase are:

(i) The cell grows in size.

(ii) New DNA is synthesized as per the old DNA templet.

(iii) Synthesis of RNA and protein takes place.

 

What is cytokinesis ?

Answer: During cell division karyokinesis (division of nucleus) is followed by the division of

cytoplasm. It is called cytokinesis. Or in other words cytokinesis is the division of

cytoplasm.

 

Explain the significance of mitosis.

Answer:

(i) It helps to maintain linear heredity of an organism by keeping the chromosome number

constant in daughter cells.

(ii) It helps in development of organism from zygotic stage to adult stage.

(iii) It is the means of repair and regeneration of cells.

(iv) Asexual reproduction is accomplished only through mitosis.

(v) Details of mitosis are similar in all organisms which emphasizes the unity of life.

 

How will you differentiate between mitosis and meiosis on the basis of the

chromosome number in the daughter cells?

Mitosis: Same diploid number of chromosomes are present in the daughter cell.

Meiosis: Haploid number of chromosomes are present in the daughter cells.

 

Why is meiosis referred to as reduction division ?

Answer: The meiosis is referred to as reduction division because the number of

chromosomes in the daughter cells is half than that of the mother cell.

 

What is the importance of meiosis?

Answer: The meiosis is important to maintain the constant number of chromosomes in a

species. It also brings about variations which result in the evolution or origin of new

species.

 

The mitosis is called equational division. Why

Answer: Mitosis is called equational division because during mitosis the cell divides equally

into two identical daughter cells.

 

Chromosomes are the carriers of heredity. why

Answer: The chromosomes contain gene which carry specific features to the offsprings.

 

Cell division: Process by which a cell divides into two new daughter cells.

Chromatids: Two identical parts of a chromosome called “sister” chromatids.

Centromeres: Part of a chromosome. Located near the middle of the chromatids.

(Some lie at the ends)

Centrioles: Two tiny structures located in the cytoplasm near the nuclear envelope

(membrane that surrounds the nucleus).

Chromatin: Material in the nucleus that condenses during cell division to form

chromosomes.

Crossing-over: The process responsible for variation.

 

What is a gene?

Answer: Genes are hereditary units located on a chromosomal thread. A gene can be

defined as “ultimate unit of recombination, mutation and self-reproduction”. They are

responsible for various characteristics externally shown by the plants and animals.

 

What is crossing-over ?

Answer: Crossing-over is the interchange of the parts of the chromatid of a pair of

chromosomes.

 

Why did Mendel selected pea plants for his experiment ?

Answer: Mendel selected pea plants for his experiment because of the following reasons :

1. A pea plant has many contrasting characters.

2. Self-fertilization takes place in pea plants and so it is possible to get a pure line of

traits.

3. Flowers are bisexual and hermaphrodite. Therefore, cross pollination is achieved

easily.

 

Define Mendel’s law of segregation.

Answer: Law of Segregation or the law of purity of gametes : The two members of a pair

of factors separate during the formation of gametes. They do not blend but segregate or

separate into different gametes. The gametes combine together by random fusion at the

time of zygote formation.

 

The Law of Dominance: Mendel’s law of dominance states that when parents with pure contrasting traits are crossed together, only the dominant trait will appear as the phenotype of the next generation. The recessive trait will be concealed.

 

The Law of Independent Assortment: According to the law of independent assortment, the alleles of two or more different genes are sorted into gametes (sperm and egg cells), independently of one another. It can be simplified stating that the allele a gamete receives from one gene does not influence another allele received for another gene.

 

What is monohybrid cross ?

Answer: Monohybrid cross : It is a cross where two forms of a single trait are crossed or

hybridized.

 

Why X-linked recessive diseases are more common among males than

females.

Answer: Because females have two copies of the X-Chromosome and males have only one

X- chromosome.

 

Haemophilia shows criss-cross inheritance. Why

Answer: The gene that causes haemophilia is recessive and lies in the X-chromosomes.

 

What is dihybrid cross ?

Answer: Dihybrid Cross: A cross between two parents taking into consideration alternative

traits of two different characters.

 

Dominance: The character expressed in first generation when any two individuals of

contrasting characters breed is dominant and the phenomenon is called dominance.

Mutation: Any change brought about into the genetic composition through external or

internal factors.

Heredity: The process of transmission of parental characters to the progeny

through the generations.

Recessive character: The character which remains hidden in F1 generation and

expressed in the second-generation in the ratio of 1:2:1.

The type of gene, which in the presence of a contrasting allele is not expressed.

Alleles: Alleles are the alternative forms of the same gene. For example, tallness and

dwarfness are the two alternative forms of a gene for height and are called alleles.

The ratio of offspring on F2 generation in a dihybrid cross. 9 : 3 : 3 : 1

Name a genetic disease in which a person cannot distinguish red and green colour. Colour blindness.

 

Exact Location:

Gene:present on chromosome

Centrioles: found only in animal cells

Aster: around the centrioles of animal cells.

 

Four nitrogenous bases: TAGC

Thymine,adenine,guanine,cytosine

 

Full name of DNA: Deoxyribonucleic acid

Autosomes: chromosomes other than sex chromosomes. 22 pairs i.e. 44 chromosomes

Sex chromosomes: xx in females and xy in males i.e. one pair

 

FIGURE BASED QUESTION

Analysis:

·         It is plant cell, because centrosome is absent and spindle apparatus not connected to it

·         It is Prophase. Chromosomes become visible as fine, long threads.  The nuclear membrane disappears.

·         The largest phase of a normal cell cycle.

Analysis: (Metaphase)

·         In this stage the chromosome lie in one plane at equator and gets attached to a spindle fibre by its centromere.

·         The stage when chromosomes arrange at the equator.

Analysis: (Anaphase)

·         The centromeres divide, the spindle fibres contract and move towards opposite poles, pulling the daughter chromosomes apart.

·         chromosomes are thickest and shortest in anaphase.

·         Separation of sister chromatids takes place.

Analysis: (Telophase)

·         Daughter nuclei.

·         The disappearance of spindle and uncoiling of chromosomes takes place.

·         Chromosomes lose their distinctiveness and gradually become transformed into chromatin network.

·         stage during which nuclear membrane and nucleoide reappear.

 

Name	Location
Asters	Around the centriole at each pole
Cell plate	In the centre of the cell.
Chromosomes	In nucleus, mitochondria and chloroplast

 

Name	Function
Chromosome	Heredity, i.e., transmission of characters from parents to offsprings.
Spindle fibres	Support chromosomes at the time of cell division.
Chiasmata	Crossing-over, in which genes are transferred from one part to another.

 

Read diffrence between mitosis, meiosis, cytokinesis, karyokinesis, PMAT, monohybrid, dihybrid, genetype, phenotype, Y-linked inheritance, X-linked inheritance, Homozygous, Heterozygous, Centrosome, Centromere, Cytokinesis in plant cell and Cytokinesis in animal cell.