Human Molecular Genetics - Lecture Twenty Three : What does the Genome tell us about being human ?

4 important questions on Human Molecular Genetics - Lecture Twenty Three : What does the Genome tell us about being human ?

What are Aligning Genes ?

Method of comparing two different organisms genetic sequences
  • We can observe common points and points of differences
  • Usually coding regions (exons) are aligned (and not non-coding regions introns), as these are the sequence of bases that actually translate to proteins
CONSERVED GENES :
  • Genes that are common between two species
  • Due to identical/closely similar gene sequences

How to compare genes between species ?

  • Comparing the conserved genes can identify evolutionary relationships between species that have diverged
  • Comparing the differences can identify DNA encoding differences in our biologies.
  • DIVERGENCE : When two or more populations of the same ancestral species accumulate independent genetic changes over time, eventually becoming genetically distinct species
  • CHALLENGES :
- Species may have many genetic differences
- Many genes are shared with other animals
- Function of most genes is unknown

What is a Hominid Phylogenetic Tree ?

  • Neanderthals and Homo sapiens are different species from the hominid family
  • They had a common ancestor at one point, before two populations (from this common ancestor) separated and diverged from one another
Why does this happen?
  • Different selection pressures experienced by each group resulted in different genes being selected for by nature
  • Over time, this results in the accumulation of enough genetic difference that the two groups are now distinct species
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Comparing Genes between Hominids

  • Homo Sapiens and Neanderthals : Europeans/Asians carry some Neanderthal alleles
  • 2-4% of the genome of non-Africans consists of Neanderthal allele variants
  • Whereas some Africans have none of these Neanderthal alleles
Homo Sapiens and Denisovans :
  • Denisovans were a group of primitive hominid species or homo sapien subspecies (debate over whether they were an entirely different species)
  • Melanesians (indigenous people of New Guinea, Fiji, Vanuatu) share 4-6% of Denisovan alleles

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