Evidence for Evolution and Common Ancestry: Genomics, Molecular, and Cellular Features

Genomics and the Human Genome Project

What is Genomics?

Genomics is the study of the complete set of DNA (the genome) in an organism, including all of its genes and their functions. Genomics involves sequencing, analyzing, and comparing genomes to understand genetic structure, function, evolution, and mapping of genes.

• Genome: The entire genetic material of an organism.

• Genomics vs. Genetics: Genetics focuses on individual genes and their roles in inheritance, while genomics studies all genes and their interrelationships.

What was learned through the Human Genome Project?

• The Human Genome Project (HGP) was an international scientific effort to sequence and map all the genes in the human genome.

• Key discoveries include:

  • Humans have approximately 20,000-25,000 protein-coding genes.

  • Most human DNA does not code for proteins (non-coding DNA).

  • Genomic similarities among humans are very high, with only small variations accounting for individual differences.

  • Comparative genomics revealed evolutionary relationships between humans and other organisms.

Evidence for Evolution: Morphological, Biochemical, and Geological Data

How do morphological, biochemical, and geological data provide evidence that organisms have changed over time?

• Morphological evidence: Study of physical structures (e.g., bones, organs) shows patterns of similarity and modification, indicating descent with modification.

• Biochemical evidence: Comparison of molecules such as proteins and DNA sequences reveals similarities and differences that reflect evolutionary relationships.

• Geological evidence: Fossil records and rock layers show the progression of life forms over time and document transitions between major groups.

What can DNA sequences and/or protein amino acid sequences tell us about common ancestry?

• Closely related species have more similar DNA and protein sequences.

• Comparing sequences allows scientists to construct phylogenetic trees that illustrate evolutionary relationships.

• Conserved genes and proteins (those that change little over time) indicate essential functions and shared ancestry.

Fundamental Molecular and Cellular Features Shared Across All Domains of Life

What are some of the processes that all living organisms share?

• Genetic code: All living organisms use DNA as the genetic material and share a nearly universal genetic code.

• Cellular processes: Processes such as DNA replication, transcription, and translation are conserved across all domains of life.

• Metabolic pathways: Core pathways like glycolysis and cellular respiration are found in all living organisms.

What is the structural and functional evidence for how species are related?

• All cells have a plasma membrane and use ribosomes to synthesize proteins.

• Similarities in cell structure (e.g., presence of organelles in eukaryotes) and function (e.g., ATP production) support common ancestry.

• Homologous structures (e.g., forelimbs of vertebrates) indicate descent from a common ancestor.

Table: Examples of Shared Molecular and Cellular Features

Feature	Description	Shared By
Genetic Code	Triplet codons specify amino acids	All domains of life
Ribosomes	Site of protein synthesis	All cells
ATP	Universal energy currency	All cells
Cell Membrane	Phospholipid bilayer structure	All cells

Example: The presence of cytochrome c, a protein involved in cellular respiration, in both plants and animals demonstrates a shared evolutionary origin.

Additional info: These shared features are considered evidence for the theory of evolution, supporting the idea that all life descended from a common ancestor.