Variation and Inheritance National 5 Biology Key Area 5: Variation and Inheritance National 4 Biology Key Area 4 Genetic Information

By the end of the lesson you will be able to ….. Give reasons why the actual phenotype ratio is different from the predicted. Use the Genetics specific vocabulary confidently

Actual figures vs. predicted figures in a cross 50% of gametes contain the P (purple) allele 50% of gametes contain the p (white) allele. Predicted phenotypic ratio = 3 dominant: 1 recessive

This cross was repeated and 100 offspring were produced. Predicted figures 75 purple 25 white Actual Figures 71 purple 29 white

Why are the actual and Predicted figures different? This cross was repeated and 100 offspring were produced. Predicted figures 75 purple 25 white Actual Figures 71 purple 29 white Why are the actual and Predicted figures different?

Actual figures vs. predicted figures in a cross In reality, there is often a difference between the actual phenotypes shown in F2 and the predicted phenotypes shown in F2. This is because fertilisation is a random process or the sample size could be too small.

Genetics Language! Phenotype Genotype Allele Dominant Recessive Homozygous Heterozygous True-Breeding

In the following example, name a) the characteristic b)the phenotype for each flower

Phenotype and Genotype Example Black White Black White What characteristic do you think we are looking at? What is the phenotype for each guinea pig? What is DOMINAT allele? What is the recessive allele? What is the genotype for each guinea pig? Using “heterozygous” and “homozygous”, describe each guinea pig

The physical appearance of an organism Word Meaning Phenotype Genotype Alleles Dominant Recessive Homozygous Heterozygous True-breeding The physical appearance of an organism The genes (or alleles) that an organism possesses. Usually written as letters. Different forms of the same gene. An allele that always expresses itself whether it is partnered by a recessive allele or by another like itself. Describes the variant of a gene for a particular characteristic which is masked or suppressed in the presence of the dominant variant. A recessive allele will only be expressed in the phenotype if it is paired with another recessive gene This describes a genotype in which the two alleles for the characteristic are identical. This describes a genotype in which the two alleles for a particular characteristic are different Describes an organism that on being crossed with a member of the same strain always produces more organism of exactly the same strain