Powerpoint presentation showing corssing over and independent assortment

1. Independent assortmentandCrossing over Year 12 Biology Grant McKenzie

2. Meiosis Meiosis in not just about reducing the number of chromosomes to half that found in somatic cells Going from diploid to haploid It is much more important

3. Chromosomes Each homologous chromosome has alternative forms of a gene Called alleles One allele comes from mother, the other from the father The alleles are responsible for dominant and recessive traits

4. Meiosis promotes Used to ensure that hereditary variability is maintained in a species Lies at the core of evolutionary change Without this change Organisms would not adapt to a changing environment

5. Processes that promote Variation Independent Assortment Is the random assortment of paternal and maternal chromosomes in gametes Each sperm or egg mixture of chromosome originating from mum or dad

6. Draw Picture of Independent assortment

7. The math of Independent Assortment Father Abc Mother aBC The child will be AabBcC The child will be AabBcC 23 Gametes produced by child Abc ABc AbC ABC Abc aBc aBC abC

8. The math of Independent Assortment The maths becomes more complicated with more chromosomes Can yield 223 unique was to arrange the 23 pairs of chromosome 8,388,608 possible ways This feature alone would lead to high levels of variation

9. Looking at Independent Assortment We will look at Independent assortment Dihybrid Inheritance

10. Crossing Over Also called recombination Makes the number of possibilities even greater Paternal and Maternal chromatids exchange corresponding genetic material Paternal and maternal refer to the origin of the chromosomes

12. Explore with Crossing over with Modelling clay Use modelling clay to explore crossing over Make 2 chromosomes Use different colours for the different chromosomes Explore single cross overs Explore double cross overs Always keep in your mind about alleles and the order of the genes along the length of the chromosome

13. Recombination There is no loss of gain of genetic material during recombination Just an equal exchange of genetic material

14. Segregation During Meiosis Alleles of different genes on different chromosomes segregate Segregation occurs independently of each other Individual is heterozygous at two genes AaBb The segregation of the A allele is different from the a allele is independent of the segregation of the B and b alleles There will be an equal number of AB, Ab, aB and ab gametes formed