The Left Handed DNA
Hall of Fame

As listed in Science 13 November 1998: 282 (5392): 1223, NetWatch Hot Picks
- Tom Schneider,
molecular information theorist

On your cover a very rare sight,
a helix that gave me a fright.
Did you forget that this spiral
called DNA is chiral,
and it normally twists to the right?
    --- Chris Welch (
    in Chemical & Engineering News, Aug 14, 2000, page 8,
    with permission
There can be no twisted thought
without a twisted molecule.
-- R. W. Gerard
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As shown in the figures to the left and right, most DNA of living things on the earth twists as a "right-hand screw". This is the same direction as a regular wood or metal screw. Many artists will flip a picture of DNA over and reverse the twist. Although left-handed Z-DNA has been demonstrated by X-ray crystallography and scanning tunnel microscopy (STM), it only recently was established that it occurs in vivo (Schwartz et al Science 1999 Jun 11;284(5421):1841-5, New York Times, June 29, 1999).
Thanks to Boris Steipe
for this figure.
See the figure to the right, which compares normal B-DNA found in cells to the rare Z-DNA, which is the same molecule twisted the other way. Furthermore, the structure of this left-handed Z-DNA is quite different from a mirror image of B-form DNA. So most of these inverted twist pictures are incorrect. This error has become so pervasive that even well-known scientists, major scientific journals and institutes make it. For several years I was collecting these cases by tossing them into a file. On 1996 February 14, I was stunned and embarrassed that my file had grown enormous, so I created this page to alert people to the problem. (Thanks to Eric Putz at my alma mater CU's MCDB for permission to use the rotating DNA.)

(click on image for further information.)

See the Right Handed DNA Hall of Fame and my home page on molecular information theory too!

For your first visit to the Left Handed Hall of Fame page I suggest that you follow the story over all of the years. After that you can look at each year individually from the table below. Note: just because a year has gone by does not mean we haven't found more examples for that year!

1997 and 1998 were bumper crop years
and 1999 beat them more than 2 fold. 2000 was a record year, thanks to help from friends around the world (60 of the 97 cases, 63%!). 2001 exceeded even that record! 2002 was lower - are we making headway?

Year Number of Left Handed DNAs
1964 1
... -
~1980 2
1978 1
1982 1
1983 2
... -
1989 3
1990 16 (5 from the Tessman letter)
1991 6
1992 5
1993 6
1994 4
1995 9
1996 31
1997 37
1998 37
1999 77
2000 97
2001 105
2002 57
2003 55
2004 55
2005 44 (minimizing images)
2006 17 (minimizing images)
2007 26 (no images, sorry)
2008 16 (no images, sorry)
2009 23 (no images, sorry)
2010 26 (no images, sorry)
2011 11 (only 2 images, sorry)
2012 11 (only rare images, sorry)
2013 12 (only rare images, sorry)
2014 12 (only rare images, sorry)
2015 3 (images under Fair Use copyright policy)
2016 2 (images under Fair Use copyright policy)
2017 5 (images under Fair Use copyright policy)
2018 7 (images under Fair Use copyright policy)
2019 15 (images under Fair Use copyright policy)
2020 13 (images under Fair Use copyright policy)
2021 7 (images under Fair Use copyright policy)
2022 10 (images under Fair Use copyright policy)
2023 1 (images under Fair Use copyright policy)
All 868


    version = 1.00 of leftyear2023.txt 2023 Sep 20

    Our Story So Far: The story line, if you have not had time to follow the previous 800 or so entries (!) is my slow realization that earth is being invaded by left handed DNA people ...
    Please also enjoy a visit to my work web site.

    left handed DNA image permission requested for image
  1. The Large Scale Left Handed DNA Invasion Has Begun! A single lone right handed DNA lifts off the planetary surface to defend against 9 invading left handed DNAs! We are outnumberd 9 to 1! binoculars First reported on 2023 Sep 20, new as of 2023 Sep 20 (Thanks to Andrey Cherstvy, for pointing this one out!)

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This Left Handed DNA page was created by Tom Schneider. It is at

None of the statements on this page are intended to endorse or favor any product over other equivalent products on the market.

When a source can be identified, permission has been requested to reproduce all graphics. If someone knows who made that cute mouse (which I picked up from somewhere on the net), please tell me.


It helps if you check through the previous entries to see if you have been scooped, as I do not repeat (even for really egregious cases).

DO NOT SEND IMAGES BY EMAIL!!! If you would like to contribute examples that are on the web, please send me precise evidence that documents the case, along with all reference materials that are available. Precise web pointers are appreciated as it saves me time. If there is an image on the web just tell me where it is, please NEVER send me images that I can get from the web! I have to check them anyway and I use wget or curl to grab them (curl is part of macOS). Let me put that another way: I cannot use graphics sent to me. I only use ones I can verify from the web.


Also please indicate whether you would like to be acknowledged on this page. Your name will be listed with your email address if you do not tell me. Since I don't want to have to recall previous rules for people, please tell me how you would like to be listed each time. You may pick an alias such as Gorilla Guerilla (which is already taken).

Web Sites: For web sites, it helps a lot if you email to me three URLs:

Be sure to cut and paste these to avoid errors.

Printed Sources: I no longer accept physical examples.

Books: For books please send URL links to pages that include this information:

Image Policy

Of course this page is devoted to left handed DNA images. I do not include images that are right handed, you can save us both time and trouble by making sure the image you spot really is left handed. If an image is flat I don't include it either. I have another page for right handed DNA images but I will only put images there if I LIKE them, which will be very rare.

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date (this is a "hits-tory" ;-)number of visits
2000 Apr 208910
2000 Apr 259002
2000 Apr 269058
2000 Jul 2411091
2000 Jul 2511146
2000 Nov 314152
2000 Dec 2015737
2001 Feb 1017495
2001 May 820736
2001 May 2121125
2002 Mar 328992
2003 Jan 3041368

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Tom Schneider
origin: 1996 Feb 14
split to multiple pages: 1999 March 27
version = 2.50 of leftmaintail.html 2022 Dec 11
updated: 2023Sep20_18:45:31

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