Lecture 40 Molecular Evolution

Identify the 4 ways in which new genes are created in the genome?

1. Whole genome duplication - through polyploidy

2. Gene Duplication

3. Horizontal Gene Transfer

4. Exon Shuffling

What is the molecular clock? Why is it inaccurate? How can it be made more accurate?

The molecular clock is the HYPOTHESIS that mutation should be occurring more or less CONSTANTLY

Rate of allele fixation by drift should be more or less constant

It is inaccurate as it relies on many assumptions

made more accurate by PICKING THE RIGHT GENE

Why isn’t the rate of mutation constant across all genes?

The rate of mutation is not constant across all genes as MUTATION RATES ARE HIGHER IN INTRONS THAN EXONS

MUTATION RATE IS HIGHER AT THE 3rd POSITION OF A CODON

What are the 2 methods by which molecular phylogenies are constructed? How do they differ?

1. Distance Method - looks at OVERALL SIMILARITIES BETWEEN ORGANISMS

2. Parsimony Method - look at minimum number of changes to the CHARACTER STATE from the common ancestor

What are homologous genes? What is the difference between paralogs and orthologs?

Homologous genes are genes that are evolutionarily related, and share a common gene ancestor

• Orthologs

  • Homologous genes found in different organisms

  • RESULT FROM SPECIATION EVENTS

• Paralogs

  • Homologous genes found in THE SAME ORGANISM

  • RESULT OF GENE DUPLICATION

What is the difference between Cladogenesis and Anagenesis?

Cladogenesis is splitting WITHIN A LINEAGE

Anagenesis is EVOLUTION TAKING PLACE WITHIN A LINEAGE