Genes

Summary and Exam Tips for Genes

Genes is a subtopic of Genetics, which falls under the subject Biology in the IB DP curriculum. A gene is a heritable factor consisting of a length of DNA that influences a specific characteristic. Each gene occupies a specific position on a chromosome, known as the locus. The different forms of a gene are called alleles, which differ by only a few bases. Mutations can lead to the formation of new alleles, often through base substitution, which can be neutral, harmful, or lethal. The genome encompasses all genetic information of an organism, including DNA in chromosomes and organelles like mitochondria and chloroplasts. The Human Genome Project successfully sequenced the entire human genome, revealing insights into gene mapping, screening for genetic diseases, and understanding human ancestry. Sickle cell anemia is a genetic disease caused by a base substitution mutation in the hemoglobin gene, leading to altered red blood cells. Comparisons of gene numbers across species show that complexity isn't solely determined by gene count. Databases like GenBank can be used to compare gene sequences across species, aiding in evolutionary studies.

Exam Tips

• Understand Key Concepts: Focus on understanding what a gene is, its location (locus), and the concept of alleles. This foundational knowledge is crucial for answering questions on genetics.

• Mutations and Their Effects: Be familiar with how mutations, particularly base substitutions, can lead to new alleles and genetic diseases like sickle cell anemia. Know examples and implications.

• Human Genome Project: Remember the key outcomes of the Human Genome Project, such as gene mapping and its impact on medicine and ancestry studies.

• Use of Databases: Practice using databases like GenBank to compare gene sequences. This skill is useful for questions related to evolutionary biology and genetic comparisons.

• Comparative Analysis: Be prepared to compare the number of genes in humans with other species, understanding that gene count does not directly correlate with complexity.