BiologyCode 9700
The roles of genes in determining the phenotype
What this topic asks you to be able to do
- explain what each of these terms means: genotype and phenotype; homozygous and heterozygous; dominant, recessive and codominant; gene, allele and locus; linkage; test cross; F1 and F2
- interpret and build genetic diagrams, including Punnett squares, in order to account for and forecast the outcomes of monohybrid and dihybrid crosses involving dominance, codominance, multiple alleles and sex linkage
- interpret and draw up genetic diagrams, including Punnett squares, so as to account for and forecast the outcomes of dihybrid crosses involving autosomal linkage and epistasis
- interpret and produce genetic diagrams, including Punnett squares, to account for and forecast the outcomes of test crosses
- use the chi-squared test to find out whether the differences between expected and observed results are significant
- explain how genes, proteins and phenotype are related, using these examples: albinism, tyrosinase and the TYR gene; sickle cell anaemia, haemoglobin and the HBB gene; haemophilia, factor VIII and the F8 gene; Huntington’s disease, huntingtin and the HTT gene
- explain how gibberellin brings about stem elongation, including the roles of the dominant allele, Le, which codes for a functional enzyme of the pathway that makes gibberellin, and of the recessive allele, le, which codes for a non-functional enzyme