What is Genetics?
Genetics is the branch of biology that studies how characteristics are passed from parents to their offspring. These inherited characteristics, such as eye colour, blood group and the ability to roll your tongue, are controlled by units of information called genes.
Inside almost every cell of your body is a control centre, the nucleus. It holds thread-like structures called chromosomes, which are made of a coiled molecule known as DNA (deoxyribonucleic acid). A short section of DNA that codes for a particular characteristic is a gene. Human body cells contain 46 chromosomes arranged in 23 pairs.
Key idea
DNA is packaged into chromosomes; a length of DNA that carries the instruction for one trait is a gene. The order is: cell → nucleus → chromosome → DNA → gene.
Alleles
Because chromosomes come in pairs, genes also come in pairs. The different forms of the same gene are called alleles. For example, the gene for earlobe shape has an allele for "free" earlobes and an allele for "attached" earlobes. One allele is inherited from the mother and one from the father.
- An organism with two identical alleles (e.g. TT or tt) is homozygous for that trait.
- An organism with two different alleles (e.g. Tt) is heterozygous.
Why Genetics Matters
Understanding genetics helps doctors trace inherited diseases such as thalassaemia, which is common in Malaysia. It also allows plant breeders to develop better crops such as high-yielding oil palm and disease-resistant rice. The full set of genetic material in an organism is called its genome.
Example
A durian tree passes genes for fruit flavour and thorn shape to its seeds. A grower who understands genetics can select and breed trees that reliably produce sweet, thick-fleshed fruit.
Remember
Gene = a segment of DNA. Allele = one version of a gene. Do not confuse the two: a gene is the "topic", an allele is one "answer" to that topic.