4. DICHORIONIC, DIAMNIOTIC TWINS
Zygote split in the first two days after fertilization
Develop in different placentas and amniotic sacs
Only occur 20-30% of the time
5. MONOCHORIONIC, DIAMNIOTIC TWINS
Zygote splits after the first two days of fertilization
Grow in the same placenta and different amniotic sacs
Occur most often
7. WHAT IS IDENTICAL?
To be considered an identical twin:
have to come from the same zygote
have same blood type
have to be the same sex
have the same hair color
8. JONATHAN MILL
Study was used to determine how genes are activated
differently in identical twins
studied the genome of 22 pairs of identical twins
did have identical DNA, but they had certain differences in chemical
markings
chemical markings do not alter the DNA sequence, but they do
leave marks on genes
9. NATURE VS. NURTURE
Genes = Nature
Environment = Nurture
Manel Esteller
studied 49 pairs of identical twins
determine that epigenetic analysis could differentiate between
twins in a criminal case
10. EVERY BRAIN IS UNIQUE
Life experience influences brain differences
change the strength of connections between certain neurons
Jumping Genes
genes that paste copies of themselves into the genome
causes cells to act differently
can lead to differences in cognitive abilities, personality
traits, and susceptibility to neurological problems
11. TESTS USED TO IDENTIFY DIFFERENCES
High resolution cameras
Fingerprinting
Iris scanners
13. GENE EXPRESSION
Although they did possess nearly identical genomes,
closer study revealed they often differed in the number of
copies of individual gene segments. For instance, one
twin might be missing a segment, or possess more copies
of that segment than the other twin
They can develop different disorders and illnesses
14. ENVIRONMENTAL FACTORS
Fingerprints
caused by the different conditions experienced by the fetuses
in the womb
Smoking, drugs, and alcohol
Sun
Personality Differences
caused by different chemicals in the body that are affected by
a person’s lifestyle choices
