Question

What would be the number of chromosomes of aleurone cells of a plant with 42 chromosomes in its root tip cells?
A.42
B.63
C.84
D.21

Answer 1

Hint: Aleurone layer is a single layer of cells that forms the outermost layer of the endosperm which is triploid and the cells on the root tip are diploid.

Complete answer:
The Aleurone layer is the outer layer of endosperm that plays an important role in the breakdown of starch present in the endosperm to maltose and glucose by synthesizing alpha-amylase enzyme during germination.
The apical meristematic cells at the tip of the roots are vigorously dividing cells that are attached to the root cap.
The entire endosperm is triploid, that is they have three sets of the chromosome, and the root tip cells have two sets of a chromosome that are they are diploid
Now to know the number of chromosomes in one set (haploid) will be half of the diploid cell.
The number of chromosomes in the diploid cell of the root tip as given is 42, which means one set is of 21 chromosomes.

Now the aleurone layer is triploid, if one set is of 21 chromosomes, three sets will have 21 × 3=63 chromosomes
So the cells of the aleurone layer of the given plant will have 63 chromosomes.

Option B: The aleurone cells of the plant having 42 chromosomes in the root tip cells will have 63 chromosomes. Therefore, this is the correct option.

All other options are irrelevant.

Hence, the correct answer is option (B)

Note: The chromosome number in one set (haploid) varies in different plants and animals. Examples: There are 23 chromosomes in a haploid set of chromosomes in a human being whereas for rats, there are 19 chromosomes and for Ophioglossum that is a type of fern, the haploid set contains 639 chromosomes and onion have only 8 chromosomes in a haploid set.