Select the correct option: I II ( a ) Synapsis aligns homologous chromosomes ( i ) Anaphase – II ( b ) Synthesis of RNA and protein ( i i ) Zygotene ( c ) Action of enzyme recombinase ( i i i ) G 2 – phase ( d ) Centromeres do not separate but chromatids move towards opposite poles ( i v ) Anaphase – I ( v ) Pachytene

( a ) ( i i ) ( b ) ( i i i ) ( c ) ( v ) ( d ) ( i v )

( a ) ( i i ) ( b ) ( i ) ( c ) ( i i i ) ( d ) ( i v )

( a ) ( i ) ( b ) ( i i ) ( c ) ( v ) ( d ) ( i v )

( a ) ( i i ) ( b ) ( i i i ) ( c ) ( i v ) ( d ) ( v )

Match the following with respect to meiosis (a) Zygotene (i) Terminalization (b) Pachytene (ii) Chiasmata (c) Diplotene (iii) Crossing over (d) Diakinesis (iv) Synapsis Select the correct option from the following

(a)-(iv), (b)-(iii), (c)-(ii), (d)-(i)

(a)-(i), (b)-(ii), (c)-(iv), (d)-(iii)

(a)-(ii), (b)-(iv), (c)-(iii), (d)-(i)

(a)-(iii), (b)-(iv), (c)-(i), (d)-(ii)

Chiasma formation occurs in

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Select the correct option:

	I		II
( $a$ )	Synapsis aligns homologous chromosomes	( $i$ )	Anaphase – II
( $b$ )	Synthesis of RNA and protein	( $i i$ )	Zygotene
( $c$ )	Action of enzyme recombinase	( $i i i$ )	$G_{2}$ – phase
( $d$ )	Centromeres do not separate but chromatids move towards opposite poles	( $i v$ )	Anaphase – I
		( $v$ )	Pachytene

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

The stage during which separation of the paired homologous chromosomes begins is

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Arrange the following events of meiosis in the correct sequence:

i. Crossing over

ii. Synapsis

iii. Terminalisation of chiasmata

iv. Disappearance of the nucleolus

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Meiosis I and Meiosis II are characterised by the separation of:

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Number of bivalents, chromatid tetrads, DNA strands, telomers present in pachytene phase of meiocyte of Maize

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Match the stages of meiosis of Column-I to their characteristic features in Column-II and select the correct option using the codes given below:

Column-I		Column–II
a.	Pachytene	(i)	The pairing of homologous chromosomes
b.	Metaphase I	(ii)	Terminalization of chiasmata
c.	Diakinesis	(iii)	Crossing-over takes place
d.	Zygotene	(iv)	Chromosomes align at the equatorial plate

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

In meiosis, crossing over is initiated at _________.

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Match the changes which occur in the chromosomes during meiosis, with the different phases of prophase-I.

	List - I		List - II
(a)	Pachytene	(i)	Compaction of chromosomes
(b)	Zygotene	(ii)	Terminalisation of chiasmata
(c)	Diplotene	(iii)	Pairing of chromosomes
(d)	Leptotene	(iv)	Dissolution of synaptonemal complex
		(v)	Recombination nodule

The correct answer is

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Choose the correct statements among the following.
(A) The stage between two meiotic divisions is called interphase
(B) During zygotene, the pairing of homologous chromosomes and synapsis takes place.
(C) Initiation of mitotic spindle takes place during metaphase
(D) In animals, mitotic cell division takes place in diploid somatic cells and not in haploid cells

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Explain the mechanism of crossing over.

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

The enzyme recombinase is required at which stage of meiosis:

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Identify the event in meiosis mediated by the enzyme recombinase.

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Dissolution of the synaptonemal complex occurs during

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

After meiosis-II, daughter cells differ from the parent cells and each other in their genotypes. This can occur because of which one of the following mechanism (s)?

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

During meiosis

I,

in which stage synapsis takes place?

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

In prophase I of meiosis, synaptonemal complex is formed between

I)

Pair of homologous chromosomes

I I)

Tetrad of chromatids

I I I)

Bivalent chromosomes

I V)

Recombination modules of non sister chromatids

EASY

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Assertion $(A) :$ In crossing over, the exchange of genetic material between two homologous chromosomes occur during both mitotic and meiotic cell divisions.

Reason $(R) :$ The process of crossing over is only possible and is mediated by recombinase.

The correct answer is:

HARD

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Define crossing over. Explain crossing over with a diagram.

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Arrange the following statements on meiosis in a correct sequence.
A) Terminalisation of chiasmata.
B) Dissolution of synaptonemal complex.
C) Homologous chromosome separation.
D) Appearance of recombination nodules.
E) Pairing of homologous chromosomes.
F) Disappearance of nuclear envelope.

MEDIUM

Life Sciences>From Molecules to Organisms: Structures and Processes>Use a model to illustrate the role of cellular division (mitosis) and differentiation in producing and maintaining complex organisms.>Growth and Development of Organisms - In multicellular organisms individual cells grow and then divide via a process called mitosis, thereby allowing the organism to grow. The organism begins as a single cell (fertilized egg) that divides successively to produce many cells, with each parent cell passing identical genetic material (two variants of each chromosome pair) to both daughter cells. Cellular division and differentiation produce and maintain a complex organism, composed of systems of tissues and organs that work together to meet the needs of the whole organism.

Match the following with respect to meiosis

(a)	Zygotene	(i)	Terminalization
(b)	Pachytene	(ii)	Chiasmata
(c)	Diplotene	(iii)	Crossing over
(d)	Diakinesis	(iv)	Synapsis

Select the correct option from the following

Chiasma formation occurs in

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