Autism, Brain, and Environment

By Richard Lathe | Go to book overview

Chapter 11
The Environmental Threat:
From Autism and ADHD to Alzheimer

More than 50 years ago the Edinburgh geneticist C.H. Waddington performed an experiment. He exposed eggs of tiny fruitflies (Drosophila) to a brief period of elevated temperature ([heat-shock]). Among the adults emerging from these treated embryos were, perhaps not so surprisingly, a number of flies with developmental abnormalities – such as anomalies of wing and body structure.

The surprise came when he bred these abnormal flies together, for the phenotype (the visible expression of the insult or deficiency) was soon expressed in offspring without any heat-shock. In other words, an [environmental] effect had somehow become [genetic.]1,2

The interpretation of this experiment is interesting. Waddington deduced that the flies carry a series of mild genetic impairments that, under normal conditions, give no discernible phenotype. Low-activity variants of developmental genes persist in the population because there is no selective pressure for their removal. But stress interferes with the activity of these genes just a little, enough to produce visible developmental abnormalities.

Then, when the abnormal male and female flies with subefficient gene variants are crossed, similar low-activity genes come together in the offspring. In these flies, now with a double dose of low activity, the same developmental abnormality appears, but without the stressor – uncovering what Waddington called an [occult] or hidden phenotype.

Other stresses have exactly the same effect. When newly-laid eggs were treated with ether, and the emerging adults were intercrossed, Waddington wrote: [individuals exhibiting the phenotype began to appear in samples of the selected stock which had not been subjected to the unusual environment.]3 The

-197-

Notes for this page

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
One moment ...
Default project is now your active project.
Project items

Items saved from this book

This book has been saved
Highlights (0)
Some of your highlights are legacy items.

Highlights saved before July 30, 2012 will not be displayed on their respective source pages.

You can easily re-create the highlights by opening the book page or article, selecting the text, and clicking “Highlight.”

Citations (0)
Some of your citations are legacy items.

Any citation created before July 30, 2012 will labeled as a “Cited page.” New citations will be saved as cited passages, pages or articles.

We also added the ability to view new citations from your projects or the book or article where you created them.

Notes (0)
Bookmarks (0)

You have no saved items from this book

Project items include:
  • Saved book/article
  • Highlights
  • Quotes/citations
  • Notes
  • Bookmarks
Notes
Cite this page

Cited page

Style
Citations are available only to our active members.
Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

(Einhorn, 1992, p. 25)

(Einhorn 25)

1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

Cited page

Bookmark this page
Autism, Brain, and Environment
Table of contents

Table of contents

Settings

Settings

Typeface
Text size Smaller Larger Reset View mode
Search within

Search within this book

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

Help
Full screen
/ 288

matching results for page

    Questia reader help

    How to highlight and cite specific passages

    1. Click or tap the first word you want to select.
    2. Click or tap the last word you want to select, and you’ll see everything in between get selected.
    3. You’ll then get a menu of options like creating a highlight or a citation from that passage of text.

    OK, got it!

    Cited passage

    Style
    Citations are available only to our active members.
    Buy instant access to cite pages or passages in MLA, APA and Chicago citation styles.

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn, 1992, p. 25).

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences." (Einhorn 25)

    "Portraying himself as an honest, ordinary person helped Lincoln identify with his audiences."1

    1. Lois J. Einhorn, Abraham Lincoln, the Orator: Penetrating the Lincoln Legend (Westport, CT: Greenwood Press, 1992), 25, http://www.questia.com/read/27419298.

    Cited passage

    Thanks for trying Questia!

    Please continue trying out our research tools, but please note, full functionality is available only to our active members.

    Your work will be lost once you leave this Web page.

    Buy instant access to save your work.

    Already a member? Log in now.

    Oops!

    An unknown error has occurred. Please click the button below to reload the page. If the problem persists, please try again in a little while.