The Key Contents from this Module are:

A genotype is an organism's set of heritable genes that can be passed down from parents to offspring.

A phenotype is an individual's observable traits, such as height, eye colour, and blood type.

A gene is the basic physical and functional unit of heredity. Genes are made up of DNA, and some act as instructions to make molecules called proteins.

An allele is one of two, or more, forms of a given gene, inherited from both parents.

Mendel's law of Segregation states that alleles segregate randomly into gametes. When gametes are formed, each allele of one parent segregates randomly into the gametes, such that half of the parent’s gametes carry each allele.

According to the law of dominance or Mendel's first law of inheritance, hybrid offsprings will only inherit the dominant trait in the phenotype. The alleles that are suppressed are called as the recessive traits while the alleles that determine the trait are known as the dormant traits.

Mendel’s second law of inheritance, the law of independent assortment states that a pair of trait segregates independently of another pair during gamete formation.

Complete dominance occurs when the phenotype of the heterozygote and the dominant homozygotes are identical.

Incomplete dominance occurs when the phenotype of F1 hybrids is somewhere between the phenotypes of the two parental varieties.

Co-dominance occurs when two dominant alleles affect the phenotype separately.

There are four different types of blood groups namely:

Blood group A
Blood group B
Blood group AB
Blood group O

The laws of probability govern Mendelian Inheritance. The multiplication and addition rules can be applied to solve complex genetics problems.