Genetics – Species, Heredity & Genes

There is a huge range of diversity or variation between organisms. This diversity is mainly due to differences in the DNA of organisms but can also be due to the effect of the environment on organisms.

What is variation? Variation : refers to the differences between members of species or population.

The members display different characteristics or traits. (E.g. height, colour etc.)

Species : A species is a group of similar organisms that are capable of naturally interbreeding with each other, to produce fertile offspring. Examples of species: humans, cats, dogs, oak tree, ash tree

Inherited Variations: are variations individuals receive from their parents and are controlled by genes (e.g. eye colour, ability to roll tongue, ear shape)

Acquired Variations: are variations individuals possess as a result of their interaction with the environment (e.g. ability to read, sun tan, dyed hair)

Heredity : Heredity is the passing on of features from parents to offspring by means of genes. Examples of heredity: passing on of eye colour from parent to offspring, passing on of hair colour, height, ability to roll tongue

Chromosomes : are coiled threads of DNA and protein that become visible in the cell during cell division.(Note: when the cell is not dividing this DNA and protein is known as chromatin)

Gene : A gene is a section of DNA that codes for a particular protein. Genes are found on chromosomes.Roles of a Gene: It contains the instructions (code) to make a particular protein. Many genes encode enzymes, which control the activities of the cell.

Genes are the units of heredity and allow characteristics (traits) to be passed on from

parents to offspring.

(Note: chromosomes are actually made up of DNA and proteins)

Gene Expression: is the way in which genetic information in a gene is decoded in the cell to make a protein. Example: Expressing a gene for hair colour or eye colour, expressing a gene to cause to production of the enzyme amylase (a protein) in a cell

By the end of this section, you should be able to: understand the range of diversity that exists among organisms define the term ‘species’ define ‘heredity’ and give an example of heredity define the term 'chromosome' and be familiar with the structure of a

chromosome define the term ‘gene’ and give a role of a gene define ‘gene expression’ and give an example of gene expression