Genome mapping and applications Notes

What Does It Mean to Map a Genome?

1. A genome map shows where genes and important DNA features sit along chromosomes.
2. This helps explain traits, diseases, and evolutionary relationships.

What Types of Genome Maps Do Scientists Use?

1. There are two main types of genome maps:
   1. Genetic linkage maps show how genes co‑inherit (relative positions).
   2. Physical maps show exact base positions on DNA.

Genetic linkage maps

1. Think of linkage maps as relationship maps.
2. They show the relative positions of genes by tracking how often traits are inherited together.
3. If two genes are close together, they tend to travel as a group during inheritance.

Physical maps

1. Physical maps answer “where exactly?”
2. They pinpoint the actual physical location, the exact base positions, of genes on DNA.
3. To build them, scientists cut DNA into fragments, sequence those pieces, and assemble them back into order.
4. This is the approach the Human Genome Project used to lay out the positions of human genes across our chromosomes.

How Do Scientists Sequence an Entire Genome?

1. There are three main steps to the process:
   1. DNA fragmentation: Break the genome into smaller, manageable pieces.
   2. Sequencing: Machines read the base order of each fragment.
   3. Assembly: Computers align overlapping fragments to rebuild the complete genome.

How Do Genomes Reveal Evolution and Ancestry?

1. Comparative genomics
   1. Comparing genomes of different species shows how closely related they are.
   2. Humans and chimpanzees share about ~98% of their DNA, supporting a close evolutionary relationship.
2. Tracing human ancestry
   1. Two useful, lineage‑tracing DNA types:
      1. Mitochondrial DNA (mtDNA): passed from mothers to all children
      2. Y chromosome: passed from fathers to sons
3. These change slowly over time, revealing migration patterns and ancestral lineages.

How Does Genome Mapping Support Medicine?

1. Identifying disease‑linked genes: researchers compare genomes of healthy vs affected individuals to find mutations associated with disease.
2. Personalized medicine: genomic information helps choose treatments tailored to a patient’s genetic profile, such as:
   1. Targeted cancer therapies
   2. Predicting drug metabolism rates
   3. Choosing effective drug dosages
3. Predicting disease risk
   1. Genome‑wide association studies (GWAS) link common DNA variants to diseases (e.g., diabetes, Alzheimer’s, heart disease).

How Does Genome Mapping Help Understand Populations?

1. Population genetics uses genome data to study:
   1. Migration routes
   2. Interbreeding events
   3. Population bottlenecks
   4. Genetic diversity

What Are the Challenges of Genome Mapping?

1. Data analysis and storage
   1. Sequencing generates massive datasets
   2. Handling, storing, and interpreting them requires powerful computing and bioinformatics.
2. Ethical considerations
   1. Who owns your genetic data?
   2. How should it be used?
   3. How do we prevent misuse (e.g., by insurers or employers)?
3. Genetic complexity
   1. Most traits are polygenic and influenced by environment.

Why Is Genome Mapping Important for the Future?

1. Healthcare transformation
   1. New drug development
   2. Personalized therapies
   3. Early disease predictions
   4. Cancer immunotherapies
2. Evolutionary biology: Genome comparison explains how species adapt and diverge, informing conservation and biodiversity efforts.
3. Agriculture and food security
   1. Genome mapping helps breeders develop crops and livestock with:
      1. Higher yields
      2. Disease resistance
      3. Better nutrition