Question

Choose the correct optionfrom a-d after reading the two statements below:

The triploid (3n) condition of endosperm is achieved by

i. Fusion of egg with the nucleus of a male gamete.

ii. Fusion of two polar nuclei and one nucleus of a male gamete.

iii. Fusion of egg with generative cell

iv. Fusion of egg with tube nucleus.

If the endosperm of an angiosperm has 24 chromosomes. The number of chromosomes in the

gametes would be

I. 8

II. 16

III. 24

IV. 48

Choose the correct option

a. ii) and I)

b. iii) and I)

c. i) and II)

d. ii) and II)​

Answer 1

Answer:

• 1. (ii) Fusion of two polar nuclei and one nucleus of a male gamete
• 2. (ii)16

So, finally option (d) is correct.

Answer 2

Answer:

The correct option will be a. ii) and I)

Explanation:

• In angiosperm the ovule develops from the placenta of the ovary which is the site of megaspore formation and from the megaspores embryo sac is developed.
• The eight nucleated cells are organized into the seven-celled embryo sac. The three cells which constitute the egg apparatus are situated at the micropylar end and it is composed of an egg and two synergids. The three antipodal cells are situated at the opposite end of the embryo sac ( which are formed from the haploid megaspore by mitosis). Two polar nuclei are present between these groups of cells, that eventually come together and fuse to form a diploid secondary nucleus. So, the mature embryo sac is a seven-celled structure.
• The pollen grains fall on the stigma and the pollen tube releases two male gametes at one of the synergids. One male gamete fertilizes the egg to form the diploid zygote, later it develops into an embryo and another one combines with the secondary nucleus to form the primary endosperm.

Hence, the triploid condition of endosperm is achieved by the fusion of two polar nuclei and one nucleus of a male gamete.

If the endosperm of an angiosperm has 24 chromosomes. then the number of chromosomes in the gametes will be 8 because endosperm contains 3n and if 3n = 24, then n = 8.

So, the correct option will be a. ii) and I)