If the number of chromosomes in the leaf of mango is 20. What would be the number of chromosomes in its endosperm, generative cell and nucellus respectively.
A )10, 20, 30
B )30, 10, 20
С )20, 30, 10
D )30, 20, 20
Answers
Option b) 30, 10, 20
- The endosperm is the result of double fertilization. An endosperm has three sets of chromosomes instead of one or two sets. Therefore it is 3n.
- The generative cell gives rise to the male gametes that travel via the pollen tube. It is haploid, n.
- The nucellus contains the female gametophyte. Sometimes the megaspore undergoes meiosis inside the nucellus. It is diploid, 2n.
- The mango leaf is made of somatic cells and is diploid, 2n.
- Therefore the endosperm is 3n = 30 chromosomes.
- The generative cell is n = 10 chromosomes.
- The nucellus is 2n = 20 chromosomes.
Given: number of chromosomes in the leaf of mango = 20
this represents 2n = 20 as mango leaf consists of somatic cells . which are diploid.
To Find: number of chromosomes in the endosperm, generative cell, and nucleus.
Solution:
- Generative cell or Reproductive cell is the gamete that is formed by reduction division or meiosis in order to maintain the ploidy of chromosomes of a particular species.
- Hence ploidy of generative cells is n.
- 2n = 20 (given)
. n = 20/2
n = 10 chromosomes in generative cells
2. Endosperm - also called triple fusion nucleus as it is formed by the fusion of second sperm nucleus with the two female polar nuclei. It has a role in storage for germination.
- Hence ploidy of Endosperm = 3n
= 3 × 10 = 30 chromosomes in . endosperm nucleus.
3. Nucellus - also called Megasporangium, carries the embryo sacs . in the ovule. It also consists of somatic cells.
- Somatic Cells are those that undergo Equational division or mitosis since it is just normal cellular division of body cells to wear off old, non - functional, and dead cells, meiosis is not required.
- Hence ploidy = 2n = 20 chromosomes in Nucellus