SASS Bio Heredity Notes

6093 Biology (2022) Chapter 19 Heredity SASS_PJY 1 ST ANDREW’S SECONDARY SCHOOL Secondary 4 Biology (6093) Chapters 19: Heredity Name: _______________________ ( ) Class: _________ Date: __________ 15. Inheritance Content • The Passage of Information from Parent to Offspring • The Nature of Genes and Alleles, and their Role in Determining the Phenotype • Monohybrid Crosses • Variation • Natural and Artificial Selection Learning Outcomes Candidates should be able to: define a gene as a unit of inheritance and distinguish clearly between the terms gene and allele explain the terms dominant, recessive, codominant, homozygous, heterozygous, phenotype and genotype predict the results of simple crosses with expected ratios of 3:1 and 1:1, using the terms homozygous, heterozygous, F1 generation and F2 generation explain why observed ratios often differ from expected ratios, especially when there are small numbers of progeny use genetic diagrams to solve problems involving monohybrid inheritance (genetic diagrams involving autosomal linkage or epistasis are not required) explain co-dominance and multiple alleles with reference to the inheritance of the ABO blood group phenotypes (A, B, AB and O) and the gene alleles (IA, IB and Io) describe the determination of sex in humans – XX and XY chromosomes describe mutation as a change in the structure of a gene such as in sickle cell anaemia, or in the chromosome number, such as the 47 chromosomes in the condition known as Down syndrome name radiation and chemicals as factors which may increase the rate of mutation describe the difference between continuous and discontinuous variation and give examples of each state that variation and competition lead to differential survival of, and reproduction by, those organisms best fitted to the environment give examples of environmental factors that act as forces of natural selection explain the role of natural selection as a possible mechanism for evolution give examples of artificial selection such as in the production of economically important plants and animals

6093 Biology (2022) Chapter 19 Heredity SASS_PJY 2 19.1 Heredity ● A hereditary trait is a characteristic that can be passed on from one generation to another. ● Genetics is the study of the inheritance of characteristics, or traits, by transmission of genetic material from one generation to another. ● Monohybrid inheritance refers to the inheritance of one characteristic or trait that has two contrasting forms. (dihybrid inheritance not in syllabus) 19.2 Basic Knowledge for Studying Heredity Chromosome, Gene and Alleles ● A chromosome is a highly coiled and condensed structure visible during cell division. It is made up of the molecule DNA (deoxyribonucleic acid). ● A gene locus (plural: loci) is the position on the chromosome where a gene is located. ● A gene is a basic unit of inheritance, born on a particular locus of a chromosome. It is a segment of DNA in a chrom