Genetics is the study of inheritance and variation of characteristics from parents to offspring. It explains how traits are transmitted and the role of genes.
Gene: unit of inheritance.
Allele: alternative form of a gene.
Genotype: genetic makeup of an organism.
Phenotype: observable characteristics.
Mendelian Genetics
Mendel’s laws describe how traits are inherited.
Law of Segregation: Alleles separate during gamete formation.
Law of Independent Assortment: Alleles of different genes assort independently.
Monohybrid Cross Example: Crossing tall (T) and short (t) plants.
Punnett Squares
Punnett squares are used to predict offspring genotypes and phenotypes.
Sex-linked Inheritance
Some genes are located on sex chromosomes (X or Y), producing sex-linked traits such as color blindness and hemophilia. Males express recessive X-linked traits more frequently than females.
DNA Structure and Function
DNA is made of nucleotides: phosphate, sugar, nitrogenous base.
Double helix structure discovered by Watson and Crick.
Stores genetic information and guides protein synthesis.
Practice Questions
Define genetics and distinguish between genotype and phenotype. (4 marks)
Explain Mendel’s law of segregation with example. (5 marks)
Construct a Punnett square for a monohybrid cross (Tt x Tt). (4 marks)
Explain the difference between autosomal and sex-linked inheritance. (5 marks)
Describe the structure and function of DNA. (5 marks)