Discussion
Arabidopsis plants have 10 chromosomes (5 pairs) in their somatic cells. How many chromosomes are present in each of the following ?
(i) egg cell nucleus in the female gametophyte
(ii) generative cell nucleus in a pollen grain
(iii) endosperm nucleus
(iv) fertilized egg nucleus
Answer: A
The counts are 5, 5, 15, 10.
The somatic number is 2n = 10, so n = 5.
- The egg cell of the female gametophyte is haploid: 5.
- The generative cell of the pollen grain is haploid: 5.
- The endosperm nucleus forms when a sperm fuses with the two polar nuclei, so it is triploid: 15.
- The fertilised egg (zygote) is diploid: 10.
The option 5, 5, 10, 15 swaps the endosperm and the zygote, and the other two treat the gametophyte cells as diploid or triploid, which they are not.
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