1. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. You will see lots of cats monohybrid dominance sex linkage multiple alleles dihybrid The coat colour of cats shows a large amount of discontinuous variation. This suggests that each cat’s coat colour is likely to be produced by the alleles of a large number of genes. Despite the complexity that this large number of genes causes, each one is inherited in the same way. parental phenotypes parental genotypes gamete genotypes offspring genotypes offspring phenotypes AA Aa thisthat AAa Aa AAAAa AAAAa ½ are this (AA) and ½ are that (Aa), the probability that it will be this is 0.5

2. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Monohybrid inheritance This is when a small number of phenotypes (usually only 2 or 3) are the result of one gene. The gene has more than one allele (often 2 but it can be more). One allele is usually dominant. This means that it is expressed whenever it is present in an individual. The other allele is recessive. It is only expressed if it is the only allele present in an individual. MM or Mmmm

3. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Incomplete or Co-dominance Sometimes the dominance of one allele isn’t complete. This usually results in three phenotypes produced by two alleles instead of two. Two phenotypes are produced by homozygous genotypes, the third phenotype is produced when an individual is heterozygous. The third condition is often intermediate between the other two phenotypes. Ss ss SS

4. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Sex linkage The locus of some genes is on the sex chromosome. The gene is only present on the X chromosome because the Y chromosome has a different structure. Females have 2 copies of these genes but males only have one since females have two X chromosomes. The ratio of males and females with particular phenotypes in a set of offspring can be unequal. X o X o or X o YX O X O or X O X o or X O Y

5. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Multiple alleles Each gene locus can have more than 2 alleles. An allele may be dominant to some alleles but recessive to others. This situation produces more than 2 different phenotypes. Each individual has 2 alleles present in their cells at any one time. BB or Bb or Bb l blblblbl bb or bb l

6. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Dihybrid inheritance A phenotype can be produced by the action of two (or more) genes, each with several alleles. The expression of the two pairs of alleles can interact directly or indirectly to produce the phenotype.

7. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Dihybrid inheritance A phenotype could be produced by the action of two (or more) genes, each with several alleles. The expression of the two pairs of alleles can interact directly or indirectly to produce the phenotype.

8. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Guess the parents!

9. Lesson Aims You will see examples of the main ways by which features are inherited. You will record an example of each inheritance pattern including a genetic diagram. monohybrid dominance sex linkage multiple alleles dihybrid Multiple gene inheritance Cat coat colour is the result of the inheritance of a large number of different genes.