Useful Science Basics for Understanding Genetics
An Introduction to Atoms, Molecules, Cells, Nuclei and Mitochondria
Oct 19, 2008
Genes instruct organisms to grow and function. More specifically, they instruct proteins, and are part of long molecules called DNA. These DNA are packed into chromosomes, which in turn reside in the organism’s cell. This definition will baffle someone unfamiliar with terms such as “molecule”, “organism” and “cell”. What do these terms mean?
Understanding Elements, Particles, Atoms, Molecules and Compounds
Genetics deals with very small units, which may be better understood by getting the gist of the following basic physics/chemistry concepts:
- A chemical element is a substance that cannot be made into simpler substances, for example, oxygen.
- A particle is a very small piece of matter, such as an atom.
- An atom is the smallest particle of an element (that is, the smallest an element can get whilst still retaining its chemical attributes).
- A molecule is a group of atoms bonded together, for example, water. Water is made up of two hydrogen atoms and one oxygen atom (more specifically, in a covalent bond).
- A compound is two or more bonded elements. A molecule isn’t always a compound because molecules can contain more than one atom from the same element.
(Definitions adapted from dictionary.com).
Introducing Cells, Tissues, Organs and Systems
A cell is an essential working unit of an organism (an individual life form). The human body is a relatable example to look at in more detail, but it’s important to remember that other organisms, such as plants and fish, also have cells. Some human cells are visible to the naked eye but most require magnification.
In Anatomy and Physiology (9th edition), published by Ross and Wilson in 2001, authors Anne Waugh and Alison Grant use a simple hierarchy for understanding the importance of cells:
- Tissues are a combination of cells. They have a specific function, such as muscle tissue or blood.
- Organs are a combination of tissues, also with their own functions, such as the kidneys.
- Systems are a combination of organs functioning together. The urinary system, for example, is an excretory system made up of the kidneys, ureters, urinary bladder and urethra.
The next logical step in this hierarchy would be the human body as whole – several systems working together.
Inside the Human Cell – Nuclei and Mitochondria
What is inside a cell? The simple answer is that cells contain several tiny important functioning structures (organelles) in a fluid called cytosol. Most cells have a large organelle called a nucleus (some cells have several nuclei). The nucleus holds instructions that tell the cell what to do, such as grow or divide. These are instructions are called genetic material.
Mitochondria are also important organelles, responsible for giving the cell energy, which they source from the body’s food intake. Waugh and Grant therefore refer to mitochondria as the “powerhouses of the cell”. Mitochondria also contain some genetic material, however, it is separate from that of nuclei.
Read What Is a Eukaryotic Cell? for more information on the cells that make up the human body. For a look into the next level of genetics, including the basics on genes, DNA, chromosomes and proteins, visit the University of Utah’s Genetic Science Learning Center site.
Sources
What is a cell?, Genetics Home Reference website, accessed 19th October 2008, no author specified.
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