A2.1.7 Evidence for a last universal common ancestor

What is one reason the genetic code is consistent across organisms?

It suggests that all life on Earth shares a common origin from a single ancestral organism.

What are some advantageous traits that may have helped LUCA's descendants succeed?

More efficient metabolic pathways and better replication mechanisms.

What is the significance of shared genes across all domains of life?

Shared genes suggest they were inherited from LUCA and indicate a common ancestry.

What conditions may have contributed to the extinction of other life forms on early Earth?

Environmental conditions that caused a bottleneck event, wiping out most forms of life.

What type of environment did LUCA likely inhabit?

An anaerobic habitat rich in hydrogen, carbon dioxide, and iron, similar to hydrothermal vents.

What is the genetic code?

The genetic code is a system that translates DNA instructions into proteins, the essential building blocks of life.

What are codons?

Codons are groups of three nucleotide bases that are read together to specify an amino acid or a start/stop signal during protein synthesis.

Give an example of a codon and its function.

The codon AUG codes for methionine and serves as a start signal for protein assembly.

Why is the genetic code considered universal?

The genetic code is consistent across almost all organisms, suggesting that all life on Earth shares a common origin.

What would we expect if life had arisen independently in different lineages?

We might expect each lineage to use entirely different genetic codes, similar to how human languages vary.

What is LUCA?

LUCA stands for the Last Universal Common Ancestor, which is the most recent common ancestor from which all current life descended.

Is LUCA the first living organism?

No, LUCA is not the first living organism, but rather the most recent common ancestor of all current life.

What evidence supports the existence of LUCA?

The near-universality of the genetic code and the identification of hundreds of conserved genes across all domains of life.

What types of genes have been found to be conserved across all life?

Genes coding for essential cellular functions, such as DNA replication, protein synthesis, and energy metabolism.

When did LUCA likely live?

LUCA likely lived more than 3.5 billion years ago.

What kind of organism was LUCA likely to be?

A simple, single-celled organism adapted to extreme environments, such as hydrothermal vents.

What was LUCA's likely habitat?

An anaerobic (oxygen-free) environment rich in hydrogen, carbon dioxide, and iron, similar to conditions near hydrothermal vents.

What role did natural selection play in LUCA's success?

Natural selection may have favored LUCA's descendants with advantageous traits, enabling them to outcompete other life forms.

What is the bottleneck effect in relation to LUCA?

The bottleneck effect refers to environmental conditions that may have wiped out most forms of life, leaving only LUCA's lineage to survive.

Why does understanding the universal genetic code and LUCA matter?

It helps answer profound questions about life's origins and evolution, with practical applications in medicine and biotechnology.

Can alternative forms of life exist?

Yes, scientists speculate about the possibility of life with different biochemistries, such as silicon-based life, on other planets or moons.

How does the universality of the genetic code benefit research?

It allows researchers to use model organisms like bacteria to study human genes and develop treatments for diseases.

What are the four nucleotide bases in DNA?

Adenine (A), thymine (T), cytosine (C), and guanine (G).

In what form are nucleotide bases read during protein synthesis?

In groups of three, called codons.

What does a codon specify?

A codon specifies a particular amino acid or a start/stop signal during protein synthesis.