Astronomy190 - Topics in Astronomy

Astronomy and Astrobiology

Lecture 7 : Biology I

Ty Robinson

Questions of the Day

• What does it mean for something to be alive?

• What is the ‘Central Dogma’ of biology?

• How has evolution led to the incredible biodiversity we see on Earth today?

The result of 4 billion years of evolution: Life’s

tremendous biodiversity

How to define life?

Order Reproduction

Growth and development

Energy utilization Response to the environment

Evolutionary adaptation

What is life made of?

Oxygen

Carbon

Hydrogen

Nitrogen

Calcium, Phosphorus, Potassium, Sulfur,Sodium, Chlorine, Magnesium

Trace elements (B, Cr, Co, Cu, F, I, Fe,Mn, Mo, Se, Si, Sn, V, Zn)

Chemical composition of the human body

(by weight)

DNA: the information molecule

Gene: a discrete unit of information represented in a DNA sequence

RNA: the multitasking

molecule

Proteins: the workhorse of the cell

• structure

• catalysts (enzymes)

• signaling

• delivery of nutrients

• transportation

• etc.

hemoglobin (blood)

p53 (spellchecker)

keratin (hair, nails)

Central Dogma of Biology

DNA

RNA

protein

transcription

translation

National Institutes of Health

Translation: RNA to proteinTranslation: RNA to protein

Transcription: DNA to RNATranscription: DNA to RNA

DNA as a “language:” 4 letter alphabet in 3 letter words

DNA as a “language:” 4 letter alphabet in 3 letter words

AUG CGA AGU GGG UGA

The Genetic

Code

Met - Arg - Ser - Gly - Stop

Mutation: a change in the base sequence of the DNA

Example:

ATA GTC TGA CTG ATG

Sickle cell anemia

Tyr - Gln - Thr - Asp - Tyr

ATA GTC AGA CTG ATG Tyr - Gln - Ser - Asp - Tyr

Darwin’s Big Idea: Evolution

Charles Darwin

HMS Beagle

Darwin’s Big Idea

Four Postulates:

1. Individuals within populations are variable.2. Variation is inherited from your parents.

3. Some individuals are more successful at surviving and reproducing than others.

4. Individuals with the most favorable variations are naturally selected.Fitness: the capability of an individual to reproduce and pass on genes to the next generation

Evolution is not goal-oriented

Natural selection in action

The peppered moth and the Industrial Revolution

Evolution operates by means of changes in trait frequencies in populations, as well as through speciation events

American Museum of Natural History

Evolution is not goal-oriented: something may ultimately be useful, but that may not be WHY it was selected at the time.

Feathers: originally selected for thermoregulation or sexual selection

Archaeopteryx

Unexpected results in evolution

Birds of paradise: sexual selection rules

Questions of the Day

• What does it mean for something to be alive?

• What is the ‘Central Dogma’ of biology?

• How has evolution led to the incredible biodiversity we see on Earth today?

Biology, viewed through an astrobiological lens:

1. The blueprints for making every aspect of life is contained within its informational molecule. On Earth, this is DNA.

3. Life diversifies into its tremendous biodiversity through the process of evolution.

4. Evolution is not goal-oriented!

2. Life on Earth is carbon-based.

Some molecules are chiral: they are non-superposable with their mirror image.

The chirality of life

On Earth, all of life’s amino acids are left-handed, and its sugars are right-handed!

Central Dogma of Biology

DNA

RNA

protein

transcription

translation

“master copy”

“working copy”