Question

Hola Neet Aspirants...

the number of meiotic and mitotic cell divisions required to form 40 male gametes and 60 female gametes in a plant with 48 chromosomes in its meiocyte...

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Answer 1

Heya !!

Here's the answer !!

Lemme explain the Gametogenesis briefly...

$\pink{ \underline{Male \: Gametogenesis : }}$


➡The sporogenous tissue(microspore mother cells) of pollen sacs undergo meiosis to form a microspore tetrad in which each tetrad constitute a microspore i.e. pollen grain.(This is called Microsporogenesis)

➡All microspores of microspore tetrad are functional.

➡The nucleus of pollen grain undergo mitosis to form two cells : a generative cell and a vegetative cell.

➡The generative cell undergo again mitosis to two male gametes.
Therefore, for meiosis -8 male gametes are formed (2 from each microspore of microspore tetrad).

Hence, Formation of 8 male gametes needs 1 meiosis and 8 mitosis.


$\purple{ \underline{Female \: Gametogenesis : }}$



➡The megaspore mother cells of carpel undergo meiosis to form a megaspore tetrad.(This is called Megasporogenesis).

➡Of the four , only one is functional and remaining three degenerate.

➡The nucleus of this Megasporagium (megaspore) undergoes mitosis (free nuclear division- karyokinesis without cytokinesis) to form two nuclei which in turn undergo mitosis and form four nuclei which in turn undergo mitosis to form 8 nuclei.(Total mitosis = 7 )

➡Three of these 8 move towards chalazal end and form antipodals and three of remaining 5 move towards micropylar end and constitute the Egg apparatus (two synergids and one egg cell) and remaining two constitute the polar nuclei of central cell.
This is now called embryosac (the female gamete)

Therefore , The formation of single female gamete requires 1 meiosis and 7 mitosis .

$\blue{ \bf{Now \: lemme \: come \: to \: your \: question : }}$


Number of meiosis for formation of 40 male gametes : 

1 meiosis= 8 male gametes

y meiosis = 40 male gametes

y × 8 = 40

y = 40/8=5 meiosis

Number of meiosis for formation of 60 female gametes : 

1 Meiosis = 1 female gamete

z Meiosis = 60 female gametes 

z = 60 meiosis

Total number of Meiosis required according to above mentioned question = 60+5= 65 Meiosis

Number of mitosis for the formation of 40 male gametes : 

1 mitosis = 1 male gamete(since 8 male gamets need 8 mitosis) 

y mitosis = 40 male gametes.

y = 40 mitosis

Number of mitosis for formation of 60 female gametes : 

7 mitosis = 1 Female gamete

z mitosis = 60 female gametes 

z = 60×7 = 420 mitosis.

The total number of Mitosis required according to the above mentioned question is 40 +420 = 460 Mitosis.

Hence , the correct option is (2) 65 and 460
The plant with 48 chromosomes in it's meiocyte is Solanum tuberosum (potato)

$\red{Hope \: This \: Helps \: You :) }$

$\green{ \boxed{ \large{ \bf{Be \: Brainly}}}}$