What you’ll learn18 learning objectivesChoose one objective for a focused lesson, or study the complete topic.17.4.1Inheritance as the transmission• Describe inheritance as the transmission of genetic information from generation to generationSyllabus objective17.4.2Genotype as the genetic make-up• Describe genotype as the genetic make-up of an organism and in terms of the alleles presentSyllabus objective17.4.3Phenotype as the observable features• Describe phenotype as the observable features of an organismSyllabus objective17.4.4Homozygous as having two identical• Describe homozygous as having two identical alleles of a particular geneSyllabus objective17.4.5Two identical homozygous individuals• State that two identical homozygous individuals that breed together will be pure-breedingSyllabus objective17.4.6Heterozygous as having two different• Describe heterozygous as having two different alleles of a particular geneSyllabus objective17.4.7Heterozygous individual will not be• State that a heterozygous individual will not be pure-breedingSyllabus objective17.4.8Dominant allele as an allele that is• Describe a dominant allele as an allele that is expressed if it is present in the genotypeSyllabus objective17.4.9Recessive allele as an allele that is• Describe a recessive allele as an allele that is only expressed when there is no dominant allele of the gene present in the genotypeSyllabus objective17.4.10Interpret pedigree diagrams• Interpret pedigree diagrams for the inheritance of a given characteristicSyllabus objective17.4.11Genetic diagrams to predict• Use genetic diagrams to predict the results of monohybrid crosses and calculate phenotypic ratios, limited to 1: 1 and 3: 1 ratiosSyllabus objective17.4.12Punnett squares in crosses which• Use Punnett squares in crosses which result in more than one genotype to work out and show the possible different genotypesSyllabus objective17.4.13To use a test cross to identify• Explain how to use a test cross to identify an unknown genotypeSyllabus objective17.4.14Codominance as a situation in which• Describe codominance as a situation in which both alleles in heterozygous organisms contribute to the phenotypeSyllabus objective17.4.15Inheritance of ABO blood groups• Explain the inheritance of ABO blood groups: phenotypes are A, B, AB and O blood groups and alleles are IA, IB and IoSyllabus objective17.4.16Sex-linked characteristic as a feature• Describe a sex-linked characteristic as a feature in which the gene responsible is located on a sex chromosome and that this makes the characteristic more common in one sex than in the otherSyllabus objective17.4.17Red-green colour blindness• Describe red-green colour blindness as an example of sex linkageSyllabus objective17.4.18Genetic diagrams to predict• Use genetic diagrams to predict the results of monohybrid crosses involving codominance or sex linkage and calculate phenotypic ratiosSyllabus objective