•Homework #1 is posted and due 9/17

•Bonus #1 is posted and due 10/24

•Discussions start M 9/10

Fig 7.5 +8.2

This subtle difference in structure has profound effects.

Fig 7.8

Connect nucleotides by covalent bond = strand(notice 5’-3’ bond)

Fig 8.11

DNA stores information, but does not do anything. The information must be expressed to be useful.

Fig 8.11

Where did this system come from?

Was RNA the first biological molecule?

The RNA Worldpg 312

Living organisms must fit all of the following criteria: (modified from Campbell “Biology”)

1. They must have organization.

2. They must have metabolism.

3. They must respond to the environment.

4. They must be able to reproduce themselves.

C

G

A

U*

RNA structure

Fig 8.2

RNA can form base pairs within single stranded molecule

Fig 8.10+9.12

RNA can form complex 3-D structures

Ribosomes (rRNA) have enzymatic activity:Enzymatic RNA=ribozyme

Fig 9.12

pg 223

Some RNA molecules have catalytic activities

Living organisms must fit all of the following criteria: (modified from Campbell “Biology”)

1. They must have organization.

2. They must have metabolism.

3. They must respond to the environment.

4. They must be able to reproduce themselves.

RNA can (theoretically) be replicated using complementary bases

Experimental determination of RNA’s ability to self-ligate…A step towards self-replication

from Freeman’s “Biological Science” (2002) chapter 3

Q: Can RNA self-ligate?

Hypos:Yes.No.

from Freeman’s “Biological Science” (2002) chapter 3

RNA’s added in aqueous solution

Without tag, flow thru

Some, with tag, bind to column

Column Chromatography

Overall RNA self-ligation improves by selection

Theoretical evolution of self-replicating RNA

Hypothetical Origin of Life

pg 214

Protein

DNA is used to produce RNA and/or proteins, but not all genes are expressed at the same time or in the same cells.How do cells control which genes are expressed?

Is thereanybodyout there?

Cells and organisms must monitor and respond to the environment.

Stimulus

Signal Transduction

Stimulus

Perception(by receptor)

EffectorResponse

Effector…

EffectorEffector

External

Internal