What is chromosome?

The human body has 46 chromosomes (23 pairs), 22 pairs of autosomes and one pair of sex chromosomes. Males have XY combinations and females have XX combinations of sex chromosomes.

When cells divide, they divide as shown below, and the number of chromosomes in the two divided cells is the same as the number of chromosomes in the cells before division.

However, there is an exception to this rule. When chromosomes enter a germ cell, the two pairs are separated and only one chromosome from each pair enters. This is because when a sperm and an egg are fertilized, the number of chromosomes in the fertilized egg is made up of 23 chromosomes from each parent, for a total of 46 chromosomes.

What is DNA？

Let's take a look at something even smaller. DNA (deoxyribonucleic acid), which contains genetic information, is found in the chromosomes. As shown in the figure below, the structure of DNA consists of two strands connected by hydrogen bonds of four types of bases: A (adenine), T (thymine), G (guanine), and C (cytosine).

The base is linked to a sugar called deoxyribose by a phosphate. The end of the phosphate is called the 5' end, and the end of the deoxyribose is called the 3' end.

• Chromosomes are a collection of DNA that carry genetic information.
• A person has 46 chromosomes (23 pairs).
• Males have an X chromosome and females have a Y chromosome.
• When a cell divides, the chromosomes also divide and increase.
• When a chromosome enters a germ cell, the chromosome does not increase. (meiosis)
• DNA has genetic information.
• DNA is made up of bases, deoxyribose, and phosphate.