This document discusses twin genetics and provides information about the two main types of twins - monozygotic (identical) and dizygotic (fraternal). It notes that monozygotic twins develop from one zygote and are genetically identical, while dizygotic twins develop from two separate eggs and sperm and are no more genetically similar than normal siblings. The document also covers special considerations in twin pregnancies and deliveries such as prematurity, twin-to-twin transfusion syndrome, mirror imaging, and monozygotic twins of different sexes.

1. Twin Genetics
A brief presentation for
Medical Terminology, American National University
By
Myra Bailey
May 2016

2. Introduction to Twin Genetics
A. A brief presentation on Twin Genetics
B. The two types of twin development
C. Special considerations

3. Two Basic Types of Twin Development

4. Monozygotic
Dizygotic

5. Dizygotic Monozygotic

6. Monozygotic Twins
A sample of Libby's placenta confirmed the twins are 100 per cent
genetically identical, despite them looking nothing alike
By SIOFRA BRENNAN FOR MAILONLINE
PUBLISHED: 07:50 EST, 24 February 2016 | UPDATED: 08:47 EST, 24 February 2016
: http://www.dailymail.co.uk/femail/article-3461832/First-identical-twins-different-skin-colour-born-UK.html#ixzz47YI6CWIB

8. Mirror Image-Monozygotic
Asymmetrically Opposite

9. Mirror Image Twins

10. Special Considerations
 Prematurity
• <38 weeks
• 38 weeks is considered normal for twins
 TTTS
• One twin transfuses blood to the other and
becomes anemic
• The donor twin receives too much blood and
hemorrhages
 Mirror Imaging
• When the heart is affected
• a valve might reverse the blood flow
 Turner Syndrome-monozygotic
• XY boy and X girl
• one normal boy and
• one girl with slow physical development, or
premature aging
 Monochorionic Monoembryonic
• Sharing the same chorionic sac and embryonic
sac
• Umbilical cord wraps around babies

11. About 28 weeks gestation

12. In Summary
• This has been a brief presentation of Twin Genetics
• Many unexplainable developments occur in twinning
• Healthy twins require careful gestational monitoring
and care

13. 3 sets non- identical
3 pair identical
3 weeks apart
1 week apart
Dizygotic
1st day of kindergarten
Louise and Louis
Dizygotic Teens

14. Credits
• www.multipletreasures.com
• www.proactivegenetics.com
• http://www.twinsuk.co.uk/twinstips/
• http://www.mindblowing-facts.org
• http://www.independent.co.uk/
• VeryWell, an www.about.com brand, By Pamela Prindle Fierro - Reviewed by a
board-certified physician. Updated April 19, 2016
• http://www.everydayhealth.com/healthy-living-pictures/wonderful-and-wacky-
facts-about-twins.aspx#07
• www.reddit.com
• http://imgur.com/gallery/Kj2YuIT
• SonStarPublications©

15. Identical Twin Dates
www.reddit.com http://imgur.com/gallery/Kj2YuIT

16. If a pair of identical male twins marry a pair of identical female twins,
their children will legally be cousins but genetically be full siblings
20 Mind-Blowing Facts You Never Knew About Twins/distractify.com650 × 433Search by image

17. Identical twins Venice Shaw, left and Inez Harries, 100 years old, are
photographed at Harries' home in Sylmar.
http://framework.latimes/2011/12/28/the-year-in-pictures-2011