IB Biology D3.2 Notes

This page contains our IB Biology notes for D3.2. By reading each one of these notes, you will fully cover the content for IB Biology 'Monogenic inheritance'.

All Topic 3 Sub-topics

A3.1: Diversity Of Organisms

(HL)A3.1: Further diversity

(HL)A3.2: Classification & cladistics

B3.1: Gas Exchanges

(HL)B3.1: Further gas exchange

B3.2: Transport

(HL)B3.2: Further transport

(HL)B3.3: Muscle & motility

C3.1: Body Systems

(HL)C3.1: Plant systems

C3.2: Defence Against Infectious Disease

D3.1: Reproduction

(HL)D3.1: Further reproduction

D3.2: Monogenic Inheritance

(HL)D3.2: Polygenic inheritance

D3.3: Homeostasis

(HL)D3.3: Further homeostasis

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Genes & Loci

Topic D3.2 focuses on inheritance of genes by offspring. Genes are defined as a heritable factor consisting of a length of DNA that influences a specific characteristic. Such an example of a characteristic is hair.

Different versions of this gene are called alleles, which each code for a different version of that characteristics. An example would be that three alleles would code for blonde, brown, or black hair, respectively. However, only one allele can occupy a position on a chromosome, called a locus.

Loci have a specific notation:

This starts with the number of the chromosome.
Then, p stands for short arm and q stands for the long arm.
Lastly, the position of the gene is listed.

For example, the human gene for the hemoglobin β-polypeptide is gene 15.4 on the short arm of chromosome 11. Its notation is thus 11p15.4.

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