Explanation: In aneuploidy the change is in one or two chromosomes and not an increase or decrease of an entire set. This makes it different from euploidy.

Explanation: Nullisomy results in (2n-2) set of chromosome, here n=7, so it will result in 12 chromosome over all.

Explanation: In Turner’s syndrome one set of sex chromosmome is lost resulting in 44+XO females who have masculine condition. This is a result of monosomy.

Explanation: In case of aneuploidy there is loss or gain in single chromosome which results in dis-balance of the genes and their products. This is a reason that aneuploids are usually lethal.

Explanation: Klinefelter syndrome results from trisomy in sex chromosome producing 44+ XXY. Turner is due to monosomy, endosperm is triploid i.e. the complete set of chromosome is increased and XP is due to mutation or deletion in gene not entire chromosome.

Explanation: In case of sex chromosome due to dosage compensation in female one of X chromosome is inactivated. This is similar to the absence of a sex chromosome, which makes sex chromosome aneuploidy less lethal.

Explanation: Non-disjunction of chromosome 13 will result in a trisomy and monosomy if the gamete is fertilized. This results in Pataeu syndrome. It is an autosomal aneuploidy.

Explanation: The chromosomes with age tend to lose the proper pairings that existed when they were in dictyotene stage as this is prolonged over decades. This leads to improper segregation causing trisomy.

Explanation: Nullysomy in chromosome is a loss of 2 chromosomes i.e. loss of a chromosomal pair. This can result from passing of both homologous chromosomes to the same pole during meiosis 1- this pole will produce trisomic gametes while the counterpart will produce nullisomic gametes.

Explanation: After the age of 35 the probability of non-disjunction in gamete leading to Down’s syndrome increases to 1/290. With increasing age it increases still further.

Explanation: Chromosome 18 trisomy will lead to Edward’s syndrome. Trisomy in chromosome 13 and 21 leads to Patau and Down’s syndrome respectively.

Explanation: In case of sexual mosaics there is loss in one of the sex chromosomes in some cells. In case of male there will thus be a mosaic of male and female parts corresponding to XY and XO depending on which part has which combination.

Explanation: In extreme klinefelter the chromosomal constitution is 44+XXXY, there are two extra X chromosomes which leads to more severe Klinefelter condition. Thus, it is tetrasomy.

Explanation: Disomy is nothing other than the normal chromosome numbers; this is having no harmful effect. The option a, b and d are however true.