Twins

TwinsAn ACE project by Bryan Yan 2I102

Agenda

• Fraternal Twins

• Identical Twins

• Semi-Identical Twins

• Siamese Twins

Fraternal Twins – What?

• Non-Identical Twins

• Small chance of having the same chromosome profile

• May be different sex

Fraternal – How?

• Two eggs are independently fertilized by two different sperm cells

• Two fertilized eggs are implanted in the uterus wall at the same time

Fraternal Twins – Who?

• More common for older mothers

• Twinning rates doubling in mothers over the age of 35

Fraternal Twins - Advances

• Advent of technologies and techniques to assist women in getting pregnant has cause the rate of fraternals to increase

Identical Twins – What?

• Nearly genetically identical

• Same sex, unless there are mutations during development

Identical Twins – How?

• Single egg is fertilized to form one zygote

• Then divides into two separate embryos

Identical Twins – When?

• Occurs approximately in every 3 out of 1000 births

• For IVF, it occurs approximately in every 21 out of 1000 births

Semi-Identical Twins – What?

• Genetically identical maternal genes

• Genetically dissimilar paternal genes

Semi-Identical Twins – How? (Type 1)

• Polar Twins

• A sperm fertilizes the ovum while the other fertilizes the polar body

• 25% genetic identity

Polar Body?

• Diploid cells in animals undergoing cytokinesis after meiosis to produce egg cells

• Sometimes divide unevenly

Polar Body?

• Most of the cytoplasm is segregated into one ovum

• Other smaller cells are called polar bodies

Semi-Identical Twins – How? (Type 2)

• Sesquizygotic twins

• Two sperms fertilize one ovum

• Form a triploid

• Triploid splits

Sesquizygotic twins

• Both cells from triploid splitting embeds on the endometrium

• Develop into identical twins

Siamese Twins – What?

• Conjoined twins

• Twins whose bodies are joined at a certain part e.g. upper chest

Siamese Twins – How?

• A fertilized egg completely separates

• But stem cells (which search for similar cells) find like-stem cells on the other twin

• Fuse the twins together

Siamese Twins – When?

• Ranges from 1:50000 births to 1:100000 births depending on country of birth

Siamese Twins – Where?

• Most common in Southwest Asia and Africa

Siamese Twins – Who?

• More common amongst females with a 3:1 ratio

References

• http://en.wikipedia.org/wiki/Twin• http://www.vtaide.com/png/George/twins.htm• http://pregnancy.about.com/od/pregnancy/a/Twin-Pregnancy.htm• http://www.pennmedicine.org/encyclopedia/em_DisplayAnimation.aspx?gcid=000058&ptid=17• http://www3.telus.net/tyee/multiples/1formed.html• http://answers.yahoo.com/question/index?qid=20080511034534AAUeVEH• http://suite101.com/article/a-third-kind-of-twins-a183863• http://multiples.about.com/cs/glossary/g/polarbody_def.htm• http://en.wikipedia.org/wiki/Polar_body• http://en.wikipedia.org/wiki/File:Gray9.png• http://en.wikipedia.org/wiki/File:Gray5.svg• http://ars.sciencedirect.com/content/image/1-s2.0-S0165460897004718-gr2.jpg• http://www.advancedfertility.com/images/ENDOCC1.JPG• http://en.wikipedia.org/wiki/Conjoined_twins• http://www.news.ku.edu/2007/may/11/images/07465_11.jpg• http://

www.sciencephoto.com/image/314150/530wm/P6800902-LM_of_human_ovum_at_the_two_cell_stage-SPL.jpg

• http://servinghimwithshakyhands.files.wordpress.com/2011/05/35-b-day-cake.jpg

References (Continued)

• http://vixstar1314.files.wordpress.com/2011/06/global-technology.jpg• http://www.twinsrealm.com/othrpics/nicoleandjaqueline.jpg• http://edu.glogster.com/media/3/12/25/45/12254586.jpg• http://blogs.telegraph.co.uk/culture/files/2010/10/ivf-getty.jpg• http://www.scientificamerican.com/media/inline/15DD5B0E-AB41-23B8-2B1E53E8573428C5_1.jpg• http://blog.f1000.com/wp-content/uploads/2011/12/090709-sperm-egg-02.jpg• http://

upload.wikimedia.org/wikipedia/commons/thumb/d/d6/Chang-eng-bunker-PD.gif/230px-Chang-eng-bunker-PD.gif

• http://upload.wikimedia.org/wikipedia/commons/thumb/f/f0/Mouse_embryonic_stem_cells.jpg/250px-Mouse_embryonic_stem_cells.jpg

• http://cwaboulder.files.wordpress.com/2010/05/numbers.jpg• http://upload.wikimedia.org/wikipedia/commons/thumb/8/86/Africa_(orthographic_projection).svg/200px-Afri

ca_(orthographic_projection).svg.png

• http://www.psdgraphics.com/wp-content/uploads/2009/06/female-sign.jpg

Thank You!