(i) It is a genetic condition in which there is an extra copy of chromosome 21 (Trisomy 21).
(ii) Mental retardation, delayed development, behavioural problems, weak muscle tone, vision and hearing disability are some of the conditions seen in these children.

Law of independent assortment states: "In case of inheritance of two or more pairs of characters simultaneously, the factors or genes of one pair assort out independently of the other pair

(i) Addition or deletion in the number of chromosomes in a cell. This is called ploidy. It is of two types Euploidy and Aneuploidy.
(ii) Euploidy is the condition in which the individual bears more than the usual number of diploid (2n) chromosomes. If an individual has three haploid sets of chromosomes, the condition is called triploidy (3n). Triploid plants and animals are typically sterile. If it has four haploid sets of chromosomes, the condition is called tetraploidy (4n). Tetraploid plants are advantageous as they often result in addition or deletion in the number of chromosomes in a cell. This is called ploidy. It is of two types Euploidy and Aneuploidy. Euploidy is the condition in which the individual bears more than the usual number of diploid (2n) chromosomes. If an individual has three haploid sets of chromosomes, the condition is called triploidy (3n). Triploid plants and animals are typically sterile. If it has four haploid sets of chromosomes, the condition is called tetraploidy (4n). Tetraploid plants are advantageous as they often result in increased fruit and flower size reased fruit and flower size.

During Replication of DNA:
(i) In one strand, the daughter strand is synthesized as a continuous strand which is called leading strand.
(ii) In the other strand, short segments of DNA are synthesized. This strand is called lagging strand. The short segment of DNA are called Okazaki fragments.

The law of segregation states that "When a pair of contrasting factors or genes or allelomorphs are brought together in a heterozygote or hybrid, the two members of the allelic pair remain together without mixing and when gametes are formed, the two separate out, so that only one enters each gamete".

Hydrogen bond which binds the nucleotides in a DNA.

The name of the segment of DNA is gene.

The dominant character or trait is axial white flower.

The both alleles are identical in homozygous condition.

Human females. have two similar sex chromosomes (XX). Hence, during meiosis at the time of gamete formation, one X - chromosome enters each gamete. Hence, all the gametes possess an X - chromosome. Therefore human females are said to be homogenetic.