what is the major constituent of a chromosome
Centromere The centromere is the specialized DNA sequence of a chromosome that links a pair of sister chromatids (a dyad).[1] During mitosis, spindle fibers attach to the centromere via the kinetochore.[2] Centromeres were first thought to be genetic loci that direct the behavior of chromosomes.
Genotype The genotype of an organism is the inherited map it carries within its genetic code. Not all organisms with the same genotype look or act the same way because appearance and behavior are modified by environmental and developmental conditions. Likewise, not all organisms that look alike necessarily have the same genotype. One's genotype differs subtly from one's genomic sequence. A sequence is an absolute measure of base composition of an individual, or a representative of a species or group; a genotype typically implies a measurement of how an individual differs or is specialized within a group of individuals or a species. So, typically, one refers to an individual's genotype with regard to a particular gene of interest and, in polyploid individuals, it refers to what combination of alleles the individual carries (see homozygous, heterozygous). The genetic constitution of an organism is referred to as its genotype, such as the letters Bb (B – dominant genotype and b – recessive genotype).