Genes

Study Notes

Genes are heritable factors consisting of DNA that influence specific characteristics and occupy specific positions on chromosomes. Alleles are different forms of a gene that differ by a few bases and are formed by mutations. The genome is the entire genetic information of an organism, and the Human Genome Project sequenced the entire human genome, revealing insights into gene mapping and genetic diseases.

• Gene — a heritable factor consisting of DNA that influences a specific characteristic.
  Example: The gene for eye color.
• Locus — the specific position of a gene on a chromosome.
  Example: The locus of the gene for hemoglobin on chromosome 11.
• Allele — a specific form of a gene differing by a few bases.
  Example: HbA and HbS alleles in sickle cell anemia.
• Mutation — a random change in the DNA sequence forming new alleles.
  Example: Base substitution mutation in sickle cell anemia.
• Genome — the entire genetic information of an organism.
  Example: Human genome consists of 46 chromosomes.
• Human Genome Project — an international project that sequenced the entire human genome.
  Example: Mapping of approximately 21,000 genes in humans.

Exam Tips

Key Definitions to Remember

• Gene: A heritable factor consisting of DNA that influences a specific characteristic.
• Allele: A specific form of a gene differing by a few bases.
• Mutation: A random change in the DNA sequence forming new alleles.
• Genome: The entire genetic information of an organism.

Common Confusions

• Confusing genes with alleles, which are specific forms of genes.
• Misunderstanding the role of mutations in forming new alleles.

Typical Exam Questions

• What is a gene? A heritable factor consisting of DNA that influences a specific characteristic.
• How do alleles differ from each other? By one or a few bases.
• What was the purpose of the Human Genome Project? To sequence the entire human genome and map human genes.

What Examiners Usually Test

• Understanding the difference between genes and alleles.
• The role of mutations in genetic variation.
• The significance of the Human Genome Project in genetics.