1. Genetics

2. Genetics is the study of the inheritance of Characteristics Which of the following do you think are characteristics? Hair colour Eye Colour

3. Sporting ability Piercings

4. Inheritable characteristics Many physical characteristics such as eye colour and shape of ears were inherited from your parents The instructions for these inherited characteristics were carried in the two cells that made you the egg and sperm

5. Examples of inherited characteritics

10. Chromosomes + Genes The nucleus of each sex cell (gamete) contains 23 thread like structures called Chromosomes

11. Chromosomes are made of protein + DNA These chromosomes carry genes Genes are chemicals found on chromosomes that pass on information from parents to children

12. When an egg and sperm cell fuse (each has 23 chromosomes) they give the individual they are creating 46 chromosomes One set comes from the mother the other from the father

13. Each characteristic will be controlled by a pair of genes If the gene from the sperm is brown eyes and the gene from the egg is brown eyes then the child will have brown eyes

14. If the gene from the sperm is for blue eyes and the gene from the egg is for blue eyes then the child will have blue eyes

15. If the gene from the sperm is for blue eyes and the gene from the egg is for brown eyes one of the genes is usually stronger and this one is the one that will be seen in the child This stronger gene is called the dominant gene The weaker gene is called recessive Brown eyes are dominant over blue eyes

16. A big letter is used to show the dominant gene while a small letter is used to show a recessive gene If b represents eye colour then B is for brown eyes and b is for blue eyes

17. Think of this example A sperm meets an egg The sperm has the gene B for brown hair The egg has the gene b for blonde hair What colour hair will the child have? H h

18. If this child marries a man with blonde hair what colour hair could their child have? Bb + bb Bb bb Brown Blonde

19. The dominant gene is the one that appears in the child when two different genes are controlling a characteristic The recessive gene does not appear in the child when two different genes are controlling a characteristic