Learning objectives
In the first part of the course special care is given to the description of the experimental protocols. This aspect should point out that the Mendelian genetics allowed for a high degree of understanding of the main mechanisms of inheritance, without the need to known the physico-chemical structure of the gene. In order to better understand this point, a number of lessons is dedicated to the resolution of problems on the Mendelian genetics and its extensions.
Aim of the subsequent part of the course (extension of the Mendelism to populations and quantitative traits) is the knowledge of a number of statistical methods which are important in the field of the genetic improvement of plants and animal (genetic of quantitative traits). Understanding of the microevolution process is favored by a detailed explanation of the mathematical aspects intrinsic to population genetics.
Analogously, several aspects of the second part of the course (Molecular Genetics) concern the description of experiments.The graduate should clearly understand “how” the researchers proved the existence of fine molecular mechanisms such as replication, transcription or deciphering the genetic code. Special care is given to molecular evolution, pointing out that that the biological molecules under examination are a common inheritance of all living organisms.
Prerequisites
Basic knowledge of mathematics, chemistry and physics
Course unit content
The aim of the course is a clear understanding of the main mechanisms of inheritance.
The first part concerns the Mendelian genetics. It covers a span of time comprised between the beginning and the half of the XX century (from rediscovery of the Mendelian laws to description of the fine structure of the gene by Benzer). Gene is described as an hereditary factor, which can be identified by the presence of at least one allele and then mapped on the chromosome by means of genetic crosses. The construction of a genetic map in bacteria and in eukaryotic organisms is explained in detail.
The subsequent part of the course is an extension of the Mendelian genetics from an evolutionary vewpoint. It concerns genetics of quantitative traits and the fate of the genetic material in populations. Since these topics are eminently quantitative, special care is given to the statistical methods.
The second part of the course concerns the molecular basis of the gene expression. Rather than a theoretical entity, the gene is now a double-stranded DNA nucleotide sequence which must be recognized by a number of proteins. The topics are the chemical structure of the genetic material, the structure of the chromosome (from the double-helix model to the compact metaphasic structure), the replication and transcription of DNA, the deciphering of the genetic code and the translation of RNA into proteins. Point mutations, DNA repair, and regulation of gene expression in bacteria are also treated in detail.
Full programme
Program of the course of Genetics for the Degree Course in Natural and Environmental Sciences (Academic Year 2022/2023)
Book: Klug, Cummings, Spencer: Concepts of Genetics, Pearson. The program of the course refers to the chapters and paragraphs of the text.
Chapter 1, Introduction to genetics
From Mendel to DNA in less than a century
The discovery of the double helix started the era of recombinant DNA
Genomics originated from recombinant DNA technology
Genetic studies are based on the use of model organisms
We live in the "era of genetics"
ID: knowledge and understanding
ID: making judgements
ID: communication skills
Chapter 2, Mitosis and meiosis
The cell structure is closely related to genetic function
In diploid organisms, chromosomes are present in pairs of homologues
Mitosis equally subdivides the chromosomes in the cells that are dividing
Meiosis reduces the number of diploid to haploid chromosomes in germ cells and spores
Gamete development is different during spermatogenesis and oogenesis
Meiosis is central to the success of sexual reproduction of all diploid organisms
ID: knowledge and understanding
ID: learning skills
Chapter 3, Mendelian genetics
Mendel used a fine experimental approach to study the mechanisms of heredity
The cross between monohybrids reveals how a character is transmitted from generation to generation
The cross between dihybrid revealed the fourth mendelian postulate: the independent assortment
Mendel's work was rediscovered in the early 20th century
The correlation between Mendel's postulates and chromosome behavior formed the basis for modern genetics of character transmission
The independent assortment leads to enormous genetic variability
The laws of probability help explain genetic events
The chi-square analysis evaluates the influence of chance on genetic data
Pedigrees reveal inheritance patterns in humans
Application of the laws of probability in determining the genotype in human family trees
ID: knowledge and understanding
ID: learning skills
Chapter 4, Extensions of the mendelian genetics
Alleles influence the phenotype differently
Geneticists use a number of different symbols for alleles
In incomplete dominance no allele is dominant
The influence of both alleles on a heterozygote is evident in codominance
Multiple alleles of a gene may exist in a population
Lethal alleles are essential genes
Phenotypes are often influenced by more than one gene
The expression of a single gene can have many effects
X-linkage indicates genes on the X chromosome
Phenotypic expression does not always directly reflect the genotype
ID: knowledge and understanding
ID: learning skills
Chapter 5, Mapping in eukaryotes
Genes linked on the same chromosome segregate together
The crossing-over is the basis for determining the distance between genes during chromosomal mapping
The determination of the gene order during mapping is based on the analysis of multiple crossing-over
The phenomenon of interference influences the possibility of observing multiple exchanges
Many Drosophila genes have been carefully mapped
The crossing-over involves a physical exchange between chromatids
Recombination also occurs between mitotic chromosomes
Mapping of human genes by somatic hybrids
ID: knowledge and understanding
ID: learning skills
Chapter 6, Genetic mapping in bacteria and bacteriophages
Bacteria spontaneously mutate and grow at exponential rate
Conjugation is a means of genetic recombination in bacteria
Transformation is another process that leads to genetic recombination in bacteria
Bacteriophages are bacterial viruses
Transduction is a virus-mediated transfer of bacterial DNA
Intragenic recombination occurs in phage T4 (locus rII)
ID: knowledge and understanding
ID: learning skills
Chapter 7, Determination of sex and sex chromosomes
The X and Y chromosomes were first associated with sex determination in the early 20th century
Dosage compensation prevents an excess of gene expression of the X chromosome in humans and other mammals
ID: knowledge and understanding
Chapter 10, DNA: structure, replication and variation
The genetic material must contain four essential properties
Until 1944, some observations favored proteins as genetic material
The first evidence that DNA was the genetic material was obtained during the study of bacteria and bacteriophages
Direct and indirect evidence supports the view that DNA is the genetic material in eukaryotes
RNA can be the genetic material in some viruses
Knowledge of the chemistry of nucleic acids is essential for understanding the structure of DNA
The structure of DNA is a key for understanding its function
The structure of RNA is chemically similar to DNA, but with a single strand
ID: knowledge and understanding
Chapter 11, Replication of DNA
Replication of DNA is semi-conservative
DNA synthesis in bacteria involves five polymerases and accessory proteins
During DNA replication many complex problems must be solved
The DNA helix must be turned
The start of DNA synthesis requires a primer of RNA
Antiparallel filaments require continuous and discontinuous DNA synthesis
The synthesis occurs simultaneously on the leading and lagging filaments
Proofreading is an integral part of the replication of DNA
A coherent model summarizes the replication of DNA
Replication is controlled by a variety of genes
Replication of eukaryotic DNA is similar to that occurring in prokaryotes, but considerably more complex
ID: knowledge and understanding
Chapter 12, The organization of DNA in chromosomes
Viral and bacterial chromosomes are relatively simple DNA molecules
Supercoiling is common in the DNA of viral and bacterial chromosomes
Specialized chromosomes reveal variations in the structure
Eukaryotic DNA is organized into chromatin
Eukaryotic chromosomes show a complex organization, characterized by repetitive DNA
The vast majority of the eukaryotic genome does not encode structural proteins or active biological molecules (e.g. ribosomal RNA or transfer RNA)
ID: knowledge and understanding
Chapter 13, Expression and regulation of the genetic material
The genetic code
Early studies pointed out the operating model of the code
Studies by Nirenberg, Matthaei and others led to deciphering the code
The code alphabet shows various interesting patterns among the 64 codons
The characteristics of the genetic code have been confirmed by experimental studies on the MS2 phage
The genetic code is almost universal
Different starting points during translation generate overlapping genes
Transcription is the process by which RNA is synthesized from a template DNA
RNA polymerase directs the synthesis of RNA
Transcription in eukaryotes differs from transcription in prokaryotes in several aspects
The coding regions of the eukaryotic genes are interrupted by intronic DNA sequences
The transcription was visualized by electronic microscopy
ID: knowledge and understanding
Chapter 14, Translation of mRNA into proteins
The translation depends on the ribosomes and the transfer RNA
The translation process in prokaryotes can be divided into three stages
The translation process in eukaryotes is more complex
The idea that proteins are important in inheritance originated from studies on congenital metabolic dysfunctions
Identification of nutritional mutants in Neurospora crassa led to the hypothesis "one gene - one enzyme"
The study of human hemoglobin established that a gene codes for a polypeptidic chain
Protein structure is the basis of biological diversity
Protein function is directly related to the structure of molecules
ID: knowledge and understanding
Chapter 15, Point mutations in protein coding genes and mechanisms of DNA repair
Mutations are classified in various ways
The spontaneous rate of mutation varies widely between organisms
Spontaneous mutations result from replication errors and chemical modification of bases
Mutations induced by exogenous factors result from DNA damage caused by chemical compounds and radiation
The Ames test is a useful tool for assessing the mutagenic power of chemical compounds
Organisms employ repair systems to protect their genetic material from mutations
ID: knowledge and understanding
Chapter 16, Regulation of gene expression in prokaryotes
Prokaryotes possess effective genetic mechanisms for an adequately response to environmental changes
The lactose metabolism in E. coli is regulated by an inducible genetic system (lactose operon)
The tryptophan operon (trp) in E. coli is a repressible genetic system
Attenuation is a critical process in the regulation of the trp operon in E. coli
ID: knowledge and understanding
Chapter 24, Genetics of quantitative traits and multifactorial characters
Not all polygenic characters exhibit a continuous variation
Transmission of quantitative traits can be explained in Mendelian terms
The study of quantitative traits is based on statistical analysis
The coefficient of heredity in “sensu stricto” estimates the genetic contribution to the phenotypic diversity
ID: applying knowledge and understanding
Chapter 25, Population genetics
The allelic frequencies of the gene pool of a population can vary in space and time
Hardy-Weinberg's law expresses the relationship between allelic and genotypic frequencies in an ideal population
Hardy-Weinberg's law can be applied to human populations
Natural selection is the main driver of the change in allele frequencies
The mutation generates new alleles in a gene pool
Migration and genetic drift can alter the allelic frequencies
Genetic drift determines random changes in the allelic frequencies in small populations
The non-random coupling changes the genotypic frequencies but not the allelic frequencies
ID: knowledge and understanding
Bibliography
Klug W.S, Cummings M.R. Concetti di Genetica. Pearson Editore
Teaching methods
Frontal lessons (a small part of the course, about four hours, is addressed to the resolution of Mendelian genetics problems).
Assessment methods and criteria
Oral examination, with the aim to assess the ability of the student to explain, with a good care of language, both topics of Mendelian genetics and of molecular genetics.
Other information
Is appreciated a basic knowledge of the English language
2030 agenda goals for sustainable development
- - -
