A reduction step during meiosis is important because:

  • It returns the chromosome number to normal before fertilization

  • There is a mechanism for this

  • Only one copy of each chromosome is necessary

  • Otherwise chromosome copies would double each fertilization

Which of the following statements about meiosis is false?

  • Haploid cells cannot divide meiotically

  • DNA replication does not occur during interkinesis

  • Assortment of homologous chromosomes on the equatorial plate during metaphase I is independent

  • Of the four cells produced by meiosis, none are genetically identical to the parent cells but two are identical to each other

Number of chromosomes in onion root tip cell at G1 phase will be

 

  •       16

  •       12

  •       8

  •      6

D, E, F and G are the four daughter cells resulting when cell A undergoes meiosis as shown in the following diagram. If no crossing over has occurred which cells listed below, if any, are genetically identical?

  • Cells B and C                               

  • No two cells

  • Cells D and E, cells F and G         

  • Cells D, and F, Cell E and G

The DNA content of individual cells and the number of cells in each phase of a "cell cycle" can be determined, using flow cytometry. Which of the following combinations of "phase of a cell cycle and its corresponding DNA content" can be considered normal?
A. Diploid cells found in the Go or G1 phase.
B. Cells with twice the normal DNA content in the early M phase.
C. Cells with intermediate amounts of DNA in the S Phase.
D. Cells with twice the normal DNA content in the G2 phase.

  • A and B               

  • B and C             

  • C and D             

  • All are correct

Let a cell's generation time is 1 minute. In 20 minutes a culture tube (culture medium) is 1/8th filled with cells. When the tube will be fullfilled?

  • 21 minutes     

  • 23 minutes     

  • 60 minutes     

  • 160 minutes

The following diagram refers to a typical cell cycle.

Identify the parts marked as X, Y and Z.

  • X - G1; Y - S; Z - G2                     

  • X - G2; Y - S; Z - G1

  • X - G0; Y - S; Z - G2                     

  • X - G1; Y - G2; Z - G0

Identify the meiotic stage in which the homologous chromosomes separate while the sister chromatids remain associated at their centromeres:

  • Metaphase I    

  • Metaphase II  

  • Anaphase I     

  • Anaphase II

At which stage of meiosis does the genetic constitution of gametes is finally decided:

  • Metaphase I    

    (2) Anaphase II    

    (3) Metaphase II   

    (4) Anaphase I

  • 2
  • 3
  • 4

Select the correct statement about G1 phase:

  • Cell is metabolically inactive

  • DNA in the cell does not replicate

  • It is not a phase of synthesis of macromolecules

  • Cell stops growing

A. Most dramatic period of cell cycle
involving a major reorganization of virtually all components of the cell
B. It represents the phase when the actual cell division occurs
These statements (A & B) are concerned with

  • S-phase                               
  • G1 phase
  • M-phase                             
  • G2 phase

Select the correct statement

  • Chromosoms decondense and lose their individuality during anaphase

  • Spindle fibres attach to kinetochores of chromosomes during early prophase

  • Centriole begins to move towards opposite poles of the cell during metaphase

  • DNA is replicated during S-phase of cell cycle

Interkinesis stage of cell cycle

  • Is generally short lived 

  • Shows DNA duplication

  • Is generally long lived

  • Is followed by prophase-I

Cells that do not divide further exit G1 phase to enter an inactive stage called

  • G2 phase                 

  • G0 stage

  • S-phase                  

  • M-phase

Select the odd one out with respect to mitosis

  • It helps the organisms in both sexual and asexual reproduction

  • It is called equational division

  • It takes place only in diploid cells of plants

  • It helps in cell repair

Select the mis-matched pair

  • Leptotene – Compaction of chromosomes  continued

  • Zygotene – Appearance of recombination nodules

  • Diplotene – beginning of dissolution of synaptonemal complex

  • Diakinesis – Completgeterminalisation of chiasmata

Microtubules from opposite poles of the spindle attach to the pairs of homologous chromosomes during

  • Pachytene               

  • Metaphase – I

  • Metaphase – II         

  • Early prophase

Exchange of genetic material between two homologous chromosomes occurs in

  • Leptotene                

  • Diakinesis

  • Pachytene               

  • Diplotene

How many meiotic divisions are required to produce 50 wheat grains?

 

  • 100                         

  • 200

  • 25                           

  • 63

A typical eukaryotic cell cycle is illustrated by human cells in culture. These cells divide once in approximately every

  • 24 hours                  

  • 90 minutes

  • 20 minutes               

  • 9 hours

Choose incorrect statement with respect to cell cycle

  • Duration of cell cycle can vary from organism to organism

  • Duration of cell cycle is uniform in different cell types of an organism

  • Events of cell cycle are under genetic control

  • It is divided into two basic phases

Choose the correct sequence with respect to  different phases of cell cycle

  • G1 S, G2, M             

  • G1, G2, S, M

  • M, G2, G1, S             

  • S, M, G2, G1

Human nerve cells do not divide after birth and they remain throughout their life in which phase of cell cycle?

  • M-phase                  

  • G1 phase

  • G0 phase                 

  • Invisible phase

Various phases of cell cycle are controlled by

  • Cyclin proteins

  • Cyclin dependent protein kinases

  • Phosphorylation of cyclin dependent protein kinases

  • More than one option is correct

Amount of DNA and Number of chromosomes in G2 phase of cell cycle would be

  • Double and equal to that of in G1 phase respectively

  • Half and equal to that of in G1 phase respectively

  • Equal and half to that of in G1 phase respectively

  • Double and double to that of in G1 phase respectively

Exchange of genetic material between non-sister chromatids of homologous chromosomes in pachytene stage is facilitated by

 

  • Dynein                    

  • Recombinase

  • chiasmata                

  • Calmodulin

Plant cells do not divided their cytoplasm by forming a furrow in cell membrane like animal cells rather they divide by cell plate because

 

  • Plant cell do not have centrioles

  • Cell wall formation beings with formation of cell plate

  • Cell plate represents middle lamella between the walls of two adjacent cells

  • Plant cells are enclosed by a relatively inextensible wall

Which of the following number of cells can be expected from the human cell culture after 70hrs

  • 4

  • 8

  • Both 1 and 2

  • 2

Which of the following is a continuous process?
  •  Cell growth (in terms of cytoplasmic increase)
  •  Cell differentiation
  •  DNA duplication
  •  Cell division

Cell growth is a continuous process in terms of

 

  •       Increase in protein content

  •       Increase in DNA content

  •       Increase in cytoplasmic content

  •      Increase in RNA content

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