On completion of this module, students should be able to:
● Interpret the structure, complexity and behaviour of genes, chromosomes and genomes
● Explain the way in which these underpin and impinge upon a variety of biological systems
The aim of this module is to consolidate and build upon some of the genetics principles laid down in the level 1 module Introductory Genetics, and to provide a sound knowledge base for the advanced specialised modules in genetics and molecular biology in Level 3.
The course revolves around the gene and has six interrelated sections:
Concept of the Gene: This section describes how our concept of the gene has been influenced by key discoveries and experiments to the present day. It gives prominence to Benzer's fine structure analysis of the rII locus of T4 bacteriophage, complementation, recombination, colinearity of genes and proteins, and the molecular structure of eukaryotic genes.
Genomic Environment of the Gene: This section describes the DNA components and evolution of a eukaryotic genome, and includes tandem gene rays, mobile genetic elements and centromeres.
Meiosis and Recombination of the Gene: This section begins with a comparison between mitosis and meiosis and follows with a description of premeiotic events. The ultrastructure and behaviour of chromosomes at each substage of meiosis is described in detail, with particular emphasis upon homology, chromosome pairing and synapsis and recombination. The chiasmatype theory is reviewed with supporting evidence, before a detailed description of the distribution of chiasmata. Gene conversion in Ascobolus immersus is considered before reciprocal and non-reciprocal recombination are integrated into the double-strand break repair model of molecular recombination. Mitotic recombination is contrasted, with reference to Drosophila melanogaster and the parasexual cycle of Aspergillus nidulans.
Chromosome Environment of the Gene: Conventions on chromosome number, morphology, nomenclature and karyotyping introduce a major section on variation in chromosome number. The nature and consequences at mitosis and meiosis of aneuploidy and euploidy are considered. The classic experiment of Karpachenko prefaces a section on allopolyploidy, in which the origin, genetic segregation and evolution of this condition are described. Variation in chromosome structure is introduced by a description of the consequences of different types of chromosome breakage. Deficiencies, duplications, inversions and translocations are covered, with emphasis upon the mechanical and genetical problems arising during meiosis.
Reproductive Systems: This section covers the evolution of sex, clonal reproduction, breeding systems and sex determination.
Non-Mendelian Inheritance: Cytoplasmic inheritance is considered, with reference to endosymbionts, gene transfer and conflicts between cell compartments. This is followed by epigenetics, including methylation and post-transcriptional gene silencing, and supernumerary chromosomes.
The practicals integrate with, and complement several of the sections above, covering meiosis in Allium ursinum, and three-point linkage analysis in Drosophila melanogaster and Aspergillus nidulans.