5. Week 6 Mitochondrial DNA and Y-chromosome summary

Mitochondrial DNA and Y-chromosome Overview

• Nuclear DNA vs Mitochondrial DNA

  • 46 chromosomes in cell nucleus.

  • Mitochondrial DNA (mtDNA) found outside nucleus, powering cellular functions.

• Mitochondrial DNA Characteristics

  • Circular DNA, ~16,500 bp, with 37 genes mainly for protein synthesis.

  • High abundance per cell, with hundreds to thousands of copies in multiple mitochondria.

• Mitochondrial Inheritance

  • Maternal inheritance: mtDNA exclusively passed from mother.

  • All maternal offspring share identical mtDNA, daughters pass it on.

  • Indicates origin traceable to "Mitochondrial Eve" (190-200,000 years ago, Africa).

• Mitochondrial Mutations

  • Mutations in control region can lead to diseases characterized by fatigue and muscle weakness.

  • Hypervariable regions (HV1, HV2, HV3) are significant for identification.

• Y Chromosome Overview

  • Second smallest chromosome, passed from fathers to sons, essential for paternal lineage tracing.

  • Consists of pseudoautosomal and male-specific regions; SRY gene determines male traits.

• Y Chromosome Testing

  • Relies on STRs (more variable, useful for personal identification) and SNPs (stable, useful for ancestry).

  • 400+ Y-STRs exist; minimal haplotype includes only 9.

• Advantages and Limitations of Y-chromosome Studies

  • Useful for identifying male-specific DNA in mixed samples (e.g., rape cases).

  • Limits: cannot exclude closely related males in paternity situations.

• Evolution and Distribution

  • Traceability of haplogroups reveals historical human migration.

  • Mitochondrial and Y-chromosome both reflect ancestral lines back to "Eve" and "Adam".

• Summary

  • mtDNA: inherited from mother, 16,500 bp, used for ancestry and forensics.

  • Y-chromosome: inherited from father, direct ancestry tracing.

  • Both can trace back thousands of years, informing historical movements and relationships.