Comparative genomics- Introduction

Question 1

Briefly explain life on Earth 3.5 billion years ago

Answer 1

Life originated on Earth about 3.5 billion years ago. The 1st cellular life forms were prokaryotes and eukaryotes appeared about 2 billion years later. There are enough residual similarities among living things to suggest a common ancestor among us all. The great diversity of living forms is therefore the result of divergence.

Question 2

Explain how sequence analysis gives the most unambiguous evidence for relationships among species

Answer 2

For higher organisms, sequence analysis and the classical tools of comparative anatomy, paleontology, and embryology usually give a consistent picture. Classification of microorganisms is more difficult because it is less obvious how to select features on which to identify them and a large amount of lateral gene transfer threatens to overturn the picture of the evolutionary tree entirely.