Question

Monosomic and trisomic conditions are
(a) $2n-1,2n+1$
(b) $2n-1,2n-2$
(c) $2n+1,2n+8$
(d) $n,n+1$

Answer 1

Hint: ‘Mono’ refers to single whereas ‘tri’ means three. Numerical abnormalities or aneuploidy of the chromosome where one or more homologous chromosome copies are present. The trisomic condition in humans is seen in Down syndrome and monosomic is seen in Turner syndrome.

Complete answer:
Trisomy is a type of polysomy condition in which there is a presence of a particular chromosome instead of the normal two from each parent. Whereas in monosomy the diploid organism which lacks one chromosome of a single homologous pair is called monosomic.
- Nullisomy is a condition when the diploid organism which has lost a pair of homologous chromosomes is called nullisomic.
- Tetrasomy is a condition when a particular chromosome is represented four times that is four homologous.
- Methods of production of monosomic in plants:
  a) From haploids
  b) Backcrosses of interspecific hybrids
  c) From the partially asynaptic plants
  d) Irradiation treatment
  e) Spontaneous production
- Example of monosomic in diploids where the abnormality was not transmitted to progeny:
  a) Chromosome 4- drosophila
  b) Chromosome X- human
  c) Datura stramonium
  d) Nicotiana alata
- Examples of trisomic conditions in human:
  a) Chromosome 21- Down syndrome
  b) Chromosome 18- Edwards syndrome
  c) Chromosome 13- Patau syndrome
  d) Chromosome 8- Warkant syndrome 2
  e) Chromosome 22- Mosaic trisomy
So, the correct answer is, ‘${}^{\prime }2n-1,2n+1^{\prime }$ .’

Note:
- Allopolyploidy is a condition where multiples of haploid set chromosomes are derived from different related species. Such plants are derived by hybridization.
- Autoploidy in which similar sets of the chromosome of the same genome is present.
- A trisomy is a type of both polysomy in which there are three copies of a particular chromosome, instead of two is present as well as aneuploidy that is the presence of an abnormal number of chromosomes.