21st Century Biology

Experimental Biology for Pre-College Students: An Introduction to Modern Research Techniques and Scientific Writing

www.21bio.org

Alcohol is one of the world’s oldest drugs. Ethyl alcohol is the common alcohol found in beverages, it is abundant because it is a byproduct of yeast’s cellular respiration. When people consume large amounts of alcohol it affects the brain and can cause varied reactions: “First comes a "high," then, with larger amounts, sedation, unconsciousness,

and, in quantities large enough to be toxic, death”. Understanding how alcohol creates this eclectic spectrum of effects in people has always been difficult for scientists. Alcohol is a great solvent (it can dissolve things easily): fats dissolve particularly well. Because cell membranes in the brain are made of lipids (Fatty compounds), alcohol can seep into brain cells. However alcohol just being in the cells does not create its effects. Most recreational drugs effect people by binding to nerve receptors, and preventing the normal function of nerve transmitters

and the nervous system as a whole. Alcohol however, does not have its own nerve receptor to bind to, as do drugs like heroine and cocaine. Scientists now believe that alcohol can bind to a wide variety of nerve receptors. Because alcohol can affect different kinds of nerve receptors, it can create many different reactions. Alcohol is an addictive substance. Addicted people are said to have “alcoholism”. Scientists continue to try to understand alcohol on the molecular level to try to create a drug to treat people with alcoholism. Resources: www.dana.org/articles/dbk_0298.cfm - 18k - 25 Sep 2002

Alcohol: All Kinds of Bad

Brainstorm

Sidwell Friends School

Volume 2-Issue 1

September-October 2002

Thigmomorphogenesis2Brain Awareness Week2Zebrafish3Telemicroscopy3Chesapeake Bay Foundation4Wordfind4

Inside this issue:

Try to find your way through this fun maze!

Editors:Annie LagomarcinoAddie Leader-ZavosReid Ravin

Brain Awareness Week

A BrainA Basic Neuron

The Neurophysiology, Behavior, and Bioacoustics of Insects

Immunocytochemistry in Conjunction with the NIH

Weakly Electric Fish (WEF)

The picture on the right shows a graph of the field of an electric fish. Note that the field is strongest near the tail and rapidly weakens as the distance from the fish increases. This gives a fairly accurate sense of distance, if not an exact shape impression.

The sound that you are hearing is a “clicker” that is eating

WEF ApplicationsMilitary Sensory Applications

Electric Fish as Biosensors

Medical Applications

Non-Contact Human-Computer Interfaces

Thigmomorphogenesis

RNA Extraction

Arabidopsis

Monocots vs. Dicots

Thigmomorphogenesis Setup

Zebrafish The Zebrafish Project was Started at Sidwell Friends by Biology I StudentsGoals

Start a Zebrafish ColonyInvestigate Developmental Mutations of NotochordsWrite LiCl Treatment Protocols

Focus on Spadetail, Floating Head, and Hedgehog Mutations

Genome Duplication Events in Zebrafish Evolution

Urochordata

Cephalochordata

Ancestral chordate

Vertebrata

Chondrichthyes

Agnatha

Osteichthyes Teleosts

Zebrafish

Pufferfish

Genome duplication event

http://www.ittiofauna.org/webmuseum/agnati/

http://www.ucmp.berkeley.edu/vertebrates/basalfish/chondrolh.html

http://www.cosmiverse.com/science10260102.html

Fig. 2

Wnt

Wnt

GSK3ß

Frizzled

β-catenin

Tcf3

Hox genesNucleus

1. A neighboring cell secretes Wnt to the target cell.

2. Wnt binds to the target cell’s receptor, frizzled.

3. Frizzled blocks the GSK3ß complex, which normally phosphorylates ß-catenin.

4. Unphosphorylated ß-catenin binds to the Tcf3 complex, a transcription repressor in the nucleus.

5. Inhibiting the Tcf3 complex permits the transcription of Hox genes that regulate AP axis development.

GSK3ß

β-catenin

RNA transcriptase

Tcf3

Transcription of Hox genes

No Wnt signal

With Wnt signal

Keyinhibition

The Wnt signaling pathway

P

Ubiquitin-proteosome system

The Hox expression gradient and establishment of the AP axis

anterior posterior

The Hox expression gradient acts like a continuous spectrum of different colors. For example, the embryo’s head is determined by 100% red (the first Hox gene) and 0% other (the other Hox genes). A middle segment would be determined by 50% yellow (a middle Hox gene) and 50% green (the next Hox gene). By this mechanism, Hox regulates normal embryonic differentiation, leading to neurogenesis and organogenesis both along the anterior-posterior (AP) axis and along the dorsal-ventral (DV) axis.

anterior-determining genes

posterior-determining genes

Hox gene cluster

The mutants do develop a prechordal plate and other mesodermal derivatives,indicating that flh functions specifically in notochord development

flh mutants do develop a floor plate because they transiently express shh, suggesting that flh only partially blocks the

ability of axial mesodermal cells to induce floor-plate differentiation

The Floating Head Mutant

Cells in flh mutants thathave involuted and entered the

hypoblast show an abruptloss of flh expression.

Cells that have not enteredthe hypoblast continueto maintain normal flh

gene expression.

Gastrulationflhwt

The Sonic-You (Syu) Gene

The syu mutant is missing the syuGene and the shh signaling pathway does not

function properly, and so what theshh gene encodes cannot be

distributed.

Smoothened is a protein believedto activate an intracellular signaling cascade.

It forms a receptor complex with Patched.

Patched is a protein thought to be the receptorthat binds the shh gene and induces

conformational changes in itself and Smoothened.

Sonic-You (syu) gene encodes for sonic hedgehog (shh) protein and is

required for somite patterning.

Shh signaling pathway

When Patched represses Smoothened, the shh protein cannot beinvolved in the organization and patterning of tissues

in vertebrates or control a wide range of differentiationprocesses during vertebrate development, especially floorplate development. Mutations develop when this occurs.

Wnt4b is a protein expressed exclusively in the floor plate. If shh is missing, the wnt4b cannot

Function properly, so the lateral floor plate is notdeveloped fully, sometimes not at all. Many

mutations display these characteristics.

The Spadetail Mutant

The Spadetail gene encodes for a T-boxtranscription factor that encodes a message

that is expressed in the blastoderm soonafter initial zygote gene expression. Aftergastrulation, its expression is restricted to

paraxial mesoderm and later in the developingtail bud.

The spadetail mutant does not express the spadetail gene. The t-box gene

that corresponds to the spadetail mutantsis tbx16.

Together with another gene, ntl, spadetail mediates the signaling of fibroblast

growth factor (FGF).

FGF is responsible for trunk and tailFormation. Spadetail is responsible

Specifically for FGF signaling in the trunk non-notochordal mesoderm.

Without the spadetail gene, mutants have major trunk mesoderm deficiencies, but relatively normal tail and notochord development.

Zfin.org

spt

Trial 1

Trial 2

Trial 3

Trial 4

ZFISH Experiment 1 Experiment 2 Experiment 3 Control

Telemicroscopy & Tomography

Locations of MicroscopesCalifornia State University StanislausConfocal Microscope

National Center for Microscopy and Imaging ResearchUCSDTransmission Electron Microscope

IN-VSEEArizona State

UniversityScanning Probe Microscope