Learning Question What is fertilisation? Success Criteria • State the chromosome compliment of humans • Explain the importance of fertilisation • Be able to determine the sex of offspring from parents What is fertilisation? Fertilisation • Fertilisation is when the nuclei of the male and female gamete fuse together to form a zygote • Fertilisation gives rise to genetic variation Gametes Chromosome Number • Sperm and egg cells have 23 chromosomes – (one set) • Humans have 46 chromosomes – (two sets) Do males & females have the same chromosomes? Males and Females • In males, the two sex chromosomes are different – They are XY • In females, the two sex chromosomes are the same – They are XX Do males & females have the same chromosomes? Males and Females • Male gametes (sperm cells) can carry X or Y • Female gametes (egg cells) have only X Do males & females have the same chromosomes? Sex Determination http://www.bbc.co.uk/schools/gc sebitesize/science/21c_pre_201 http://www.youtube.com/watch? v=5XuiboCs0TA 1. Define fertilisation 2. What sex chromosomes do females have? 3. What sex chromosomes do males have? 4. Draw a punnet square to determine the chance of an offspring being male
