PPT- 3a Twins – nature and genetics

1. PPT- 3a Twins – nature and genetics Lesson objective – to learn about the genetic information and similarities and abnormalities in twins Lesson objective – to learn about the genetic information and similarities and abnormalities in twins

2. What are twins • Fraternal (Non-identical) twins are formed when two egg cells are fertilized; each egg by a different sperm so that two embryos are formed. Fraternal twins can be of the same or opposite sex and they don't have to look at all alike.Identical twins are formed when one egg after being fertilized by one sperm, divides into two halves. The two halves are genetically identical. Identical twins are usually of the same sex.Conjoined (Siamese) twins are formed exactly like identical twins, but during the split, the embryo does not separate completely to form two separate babies and the twins develop attached to one another Lesson objective – to learn about the genetic information and similarities and abnormalities in twins

3. TWINS When more than one baby grows in the womb at a time it is known as a multiple birth. When twins are born they can either look the same or not look alike at all. Meet Shane and Mark. They are identical twins. These twins look the same because the egg splits in half after fertilisation. They must be the same sex. Meet Sally and Peter. They are fraternal twins. These two do not look at all alike. In their case two eggs were released at the same time and each one was fertilised by a different sperm thus producing two different individuals. They could be different sexes like Sally and Peter. Lesson objective – to learn about the genetic information and similarities and abnormalities in twins

4. Ben and Jonathan Ben and Jonathon are twin brothers. They were only three months old when their parents were killed in a car crash. As they had no other family members to look after them, they were put up for adoption. Two different families adopted them and as they were so young they were not told about the fact that each had a twin brother for many years. A couple that lived in London adopted Ben. Ben’s father was very ambitious and had a job in a London bank. He worked very long hours and earned a good salary. His mother returned to work when Ben was four. She was a solicitor for a large firm in the City of London. Ben was encouraged to work hard at school. He was taken on expensive holidays and by the time he was sixteen, he had visited many different places around the world. After he finished school, he went to University. He then got a job in a City firm, selling stocks and shares. He soon earned a good salary and was able to buy his own flat in the centre of London. He still enjoyed his holidays and tried to combine foreign travel with sporting activities like sailing or skiing. A couple from the Midlands adopted Jonathon. His father was a teacher. His mother did not work until Jonathon was seven, when she returned to work as a nurse at the local hospital. His parents were keen churchgoers and Jonathon was confirmed when he was ten years old. Every year, his parents became involved in fundraising for a local charity. Jonathon was encouraged to help them. He worked hard at school and after going to University, decided that he wanted to be a social worker, working with children. Around this time, his parents told him that he had a twin brother. Jonathon enjoyed his work as a social worker. He remained a member of the Church and eventually married a girl who was also a churchgoer. Through his job as a social worker, he knew how to trace his twin. He eventually tracked down his brother and shortly after their thirtieth birthday, they met. Ben and Jonathon meet for the first time in thirty years It was a strange experience for both of them. They looked alike although Ben’s hair was a lot shorter than Jonathon's. They discovered that they both supported the same football team and enjoyed reading historical novels. They had both had measles and each had a birthmark on their left hand. The meeting passed very quickly and they made arrangements to contact each other again. It had been a very happy, if unusual afternoon. Lesson objective – to learn about the genetic information and similarities and abnormalities in twins

5. Lesson objective – to learn about the genetic information and similarities and abnormalities in twins

6. Lesson objective – to learn about the genetic information and similarities and anomalies in twins

7. Lesson objective – to learn about the genetic information and similarities and abnormalities in twins

8. Lesson objective – to learn about the genetic information and similarities and abnormalities in twins