Question

In plant-A, 2n= 12 and in plant B, 2n= 16, then what will be the ploidy number of cross breeding plants?
A) 14
B) 28
C) 12
D) 16

Answer 1

Hint:Chromosomes are thread-like structures located inside the nucleus of animal and plant cells. Each chromosome is made of protein and a single molecule of deoxyribonucleic acid (DNA)The number of complete sets of chromosomes in a cell is called ploidy.

Complete answer:
Chromosome number, precise number of chromosomes typical for a given species. In any given asexually reproducing species, the chromosome number is always the same. In sexually reproducing organisms, the number of chromosomes in the body (somatic) cells typically is diploid (2n; a pair of each chromosome), twice the haploid (1n) number found in the sex cells, or gametes.

In plant- A, 2n= 12, n= gametic chromosome number.
This means the number of chromosomes in a gamete of plant A is 6 and gametes will fuse to form a diploid organism having 12 chromosomes in each cell.
Similarly, gametic chromosome number for plant B is 8.
When plant A is cross bred with plant B –
Gamete from plant A with 6 chromosomes will fuse with gamete from plant B with 8 chromosomes to form a zygote with 14 chromosomes.
$\rightarrow$ Plant A: 2n=12, n=6
$\rightarrow$ Plant B: 2n=16, n=8
$Plant\, A\,\times\, Plant B: 6+8= 14$
So, the ploidy of the cross bred progeny will be 14 chromosomes.

Hence the correct answer is option A, i.e. 14.

Note:Polyploidy occurs when there are more than 2 sets of chromosomes in a cell of an organism. Polyploidy may occur due to abnormal cell division, either during mitosis, or commonly during metaphase 1 in meiosis.