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Life Science: Session 3

Body Cell Reproduction

What is a body cell?

One characteristic that is shared by all animals is that they are multicellular. Each cell that composes an animal is called a somatic or body cell — skin, muscle, and nerve cells are some examples. Each animal is composed of many different types of body cells that display amazing variation in form and function. However, despite this diversity, every body cell of an animal is identical when it comes to the organization of the hereditary material DNA. In the nucleus of each body cell, DNA is organized into chromosomes, which exist as chromosome pairs — with each member of a pair carrying the same set of genes.

This organization of chromosomes represents the animal’s genome and it carries all of the information necessary for reproducing another animal of that type. In terms of chromosome pairs, all animals of the same type are alike – that is, their body cells contain the same number and arrangement of chromosomes. The human genome, for example, consists of 46 chromosomes arranged in 23 pairs. The genome of a fruit fly consists of eight chromosomes arranged in four pairs.

What surprises many people is that every body cell of an animal — indeed, of any multicellular organism — carries its entire genome. Cells end up being different from one another because different genes within the genome direct their development.

How do body cells reproduce?

The cell theory states that all cells arise from pre-existing cells. Body cells are formed when existing body cells divide. When this happens, it is necessary to pass the entire genome to the resulting two daughter cells in order to ensure that each gets a complete set of chromosomes. How does this happen? Prior to cell division, all of the chromosomes of the parent cell duplicate. Then, each chromosome is passed to each daughter cell. It is critical that this orderly and precise process happens every time a body cell divides. If it doesn’t, daughter cells won’t form properly (or at all) and this may have a negative impact on the entire organism. The scientific name for this process, which is illustrated in the animation below, is mitosis.

mitosis animation

START mitosis animation

What is the role of body cell reproduction in an animal life cycle?

All animals lives begin when the sex cells of two parents unite to form the first body cell of the offspring — the fertilized egg. As important as this is in an animal life cycle, that single cell represents the only goal of sex cell production. After that first body cell forms, body cell reproduction is the process by which animals grow and develop, and by which new cells are produced and worn out cells replaced. Body cell reproduction thus occurs throughout an animal’s life span and is the dominant form of cell reproduction during a life cycle.

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