The name already gives away what inhertance is, doesn’t it? To get to the point… inherited characteristics are controlled by genes. These genes may have different forms. Different forms of the same gene are called alleles. Allelles can be either dominant or recessive. If we’re going to focus on the characteristics then here is an example for you. For eye colour, Brown is dominant and blue is recessive. This means that in a brown/blue pair the brown is dominant.

Where can we find genes? Well, taking a journey through the sex cells (also known as gametes) if we just look at a sex cell from a bird’s-eye vew you can already see what it looks like but not with a naked eye but with a microscope. If we focus on an egg cell (female) in the nucleus you would find tiny strands of chemicals called chromosomes which are made up of DNA molecules and in those chromosomes you would find genetic information (known as genes) from the mother and in those genes you would find a  substance called the DNA. Interesting. And what about a male gamete?

A male gamete as you may know is called a sperm. A sperm also holds the DNA in the gene from the chromosomes and from the nucleus. Mouthful, isn’t it? But once the sperm mates with the egg cell, genetic information is mixed (information from the father, and information from the mother) creating a fetus throughout time. But depending on the information that the mother or father carries has a huge effect on the child.

Genetic diagrams are used to represent what’s happening. The rule is to use a Capital letter for Brown, and a lower case letter for blue.


Inherited diseases. That is a mean word. Inherited diseases are caused by genes. Just having one faulty gene has a huge impact on ourselves, which can be passed on for generations. Common diseases like Huntington’s Disorder and Cystic Fibrosis.

Huntington’s disorder…

  • …affects the nervous system.
  • …is caused by a dominant allele. This means by just having one of these alleles will give you the disease.

Cystic Fibrosis…

  • …affects the cell membranes causing certain cells to produce so much mucus that it affects breathing and digestion.
  • …is carried by a recessive allele.

Two recessive alleles is the combination of the disease.


As I have mentioned before, sex chromosomes are found in the nucleus. Sex chromosomes determine wether you are male or female. There are two types of sex chromosomes and they are ‘X’ and ‘Y’.

Girl:                  Boy:
XX                    XY



  • …occur in long strings calles chromosomes.
  • …are located inside the nucleus of a gamete.

Chromosomes are made up of DNA molecules. DNA molecules are…

  • …made up of two strands
  • …coiled to form a double helix

DNA molecules form a complete set of instructions for…

  • …how the organism should be constructed.
  • …how each cell should function

2 Responses to Inheritance

  1. *-crazy-* says:

    what about uninherited or environmental dieseases?

  2. *-crazy-* says:

    sorry not that, environmental inheritance

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