To go further in Cytogenetics, we need to know more about the chromosome. Chromosomes play an important role in our body.

• Transmit the genetic information from cell to cell and from generation to generation.
• Control cellular function and development.

How human chromosomes look like in Cytogenetics?

Figure 1: Normal Chromosome Set (2n)

In the study of Cytogenetics, recognition of different types of chromosomes is very important. Human contains 22 pairs of autosomal chromosomes and a pair of sex chromosomes. Total are 46 chromosomes. Sex chromosomes include chromosome X and chromosome Y. Normal male has 46, XY chromosomes and normal female has 46, XX chromosomes which is shown in the Figure 1.

As we can see, there are different lengths between the chromosomes. The structure of chromosome can be divided to four parts: p arm, q arm, centromere and telomere. Figure 2 is the example of the structurally distinct between the chromosomes.

Figure 2: Structure of Chromosome

From figure 2, the chromosomes can be categorized into 3 types according to the position of the centromere on that chromosome: metacentric chromosome, submetacentric chromosome, and acrocentric chromosome.

Only sex chromosomes differentiate us from male to female. The rest are same for both sexes. It is important to maintain this number of chromosome for us to be a normal human. If anyone deviates from 46, XX or 46, XY, he can be considered as abnormal. Most probably it will cause that person to death. Human cannot have extra chromosome or less chromosome even small part of it.

However, the chromosomal abnormality still occurred among us. The chromosomal abnormality can be either inherited from the parents or occurred spontaneously (de novo) during the zygote is formed. There are many famous chromosomal abnormalities: Down Syndrome, Patau Syndrome, Prader-willi Syndrome, Edward Syndrome, Turner Syndrome and so on. I will talk more about these genetic disorders in coming posts. We will look through deeply on the study of human Cytogenetics and Cancer Research.