3.4 Inheritance

This page covers fundamental concepts of inheritance in IB biology, including blood types, genetic terminology, and inheritance patterns.

The ABO blood group system classifies blood into four types based on the presence of antigens on red blood cells. This system is crucial for understanding blood type antigens and antibodies, as well as determining compatible blood donors and recipients.

Vocabulary:

• Genotype: The combination of alleles of a gene
• Phenotype: The physical trait expressed by a genotype
• Allele: Different versions of a gene resulting in characteristic variation
• Homozygous: Two of the same alleles (e.g., DD or dd)
• Heterozygous: Two different alleles (e.g., Dd)
• Hemizygous: Only one allele present
• Codominant: Two dominant alleles are expressed
• Incomplete dominance: Partial expression of the recessive allele

The page also introduces the concept of sexual reproduction, which involves the fusion of gametes from each parent. Gametes segregate during meiosis to prevent indefinite chromosome duplication.

Highlight: The ABO blood type classification system uses the presence of antigens on red blood cells and antibodies in plasma to determine blood types.

A detailed chart is provided, showing the antigens, antibodies, and donor/recipient compatibility for each blood type (A, B, AB, and O). This information is essential for understanding blood groups and their characteristics.

Example: Type O blood is the universal donor as it has no A or B antigens, while type AB is the universal recipient as it has no antibodies against A or B antigens.

The page also covers genetic inheritance concepts such as Punnett squares, monohybrid and dihybrid crosses, and pedigree charts. These tools are used to predict and analyze inheritance patterns in IB biology inheritance patterns examples.

Definition: A test cross is a method used to determine unknown genotypes by crossing an individual with a recessive homozygote.

Lastly, the page introduces sex-linked inheritance and mutations:

Highlight: Sex-linked traits are carried on the X chromosome in the non-homologous region and are always expressed in males. Examples include hemophilia and color blindness.

Definition: A mutation is a change in the nucleotide sequence of a section of DNA for a particular feature, often caused by mutagens.

This comprehensive overview provides a solid foundation for understanding inheritance patterns, blood types, and genetic concepts in IB Biology syllabus topic 3.4.