Biology Genetics Lecture 1 (1860s Mendel published his research on…
Biology Genetics Lecture 1
1860s Mendel published his research on inheritance of unit factors. Cytologists describe chromosomes and their behavior during mitosis and meiosis
1900s rediscovery of Mendel's work. Chromosomes behave like unit factors. The term "Gene" proposed to replace unit factors. Genetics becomes a discipline in itself.
1905 William Bateson first uses the term genetics to describe the study of inheritance.
1940s confirmation that genetic material is not protein.
1950s Watson and Crick describe double helical structure of DNA- Molecular Biology Era begins.
1960s Cracking the triplet code and defining the pathway of information flow:DNA makes RNA makes protein
1970s Discovery of restriction enzymes: Recombinant DNA technology becomes possible. Expression of human growth hormone in E.coli. Discovery of split genes in eukaryotes- introns and exons, methods of sequencing DNA.
1990s Genome sequencing: Human, plant, drosophilia, nematode , microbial genomes and many other genomes sequenced.
James Watson, Francis Crick and Rosalind Franklin
Within cells structures called chromosomes contain genetic material in the form of DNA (deoxyribonucleic acid)
Each chromosome contains one long DNA molecule with hundreds of or thousands of genes. Genes are the units of inheritance. They encode information for building the molecules synthesized within a cell. The genetic information encoded by DNA directs the development of an organism and the maintenance of cells within an organism.
The molecular structure of DNA accounts for its ability to store information. Each DNA molecule is made up of two long chains arranged in a double helix. Each chain is made up of four kinds of chemical building blocks called nucleotides. and abbreviated to A, T, G, C.
3 billion nitrogenous bases in a human genome. 2 meters of DNA in each cell. There are over 3000 genetic diseases in humans which are termed mendelian due a mutation of a single gene. 30,000 genes code for proteins.
20,000 genes in 23 pairs of human chromosomes. 3 billion DNA base pairs. Not all genes are active in each cell type. Genes make RNA which is translated into proteins, the building blocks for each cell to function. Different cell types need different proteins to function. Mutations in the DNA sequence can result in no protein or incorrect proteins being formed giving rise to genetic disorders. Mutations in a single gene that give rise to a disease are called genetic defects (or mendelian disorders) e.g cystic fibrosis etc.
Only about 1% of our genome codes for proteins. Much of our genome makes RNA but does not code for protein,- termed non-coding RNAs. For many genes the sequence provides the blueprint for making a protein. Protein encoding genes control protein production indirectly. DNA is transcribed into RNA which is then translated into a protein. Gene expression is the process of converting information from gene to cellular product.
Gene based medicines
Dominant diseases: The strategy may require the suppression of the expression of the mutant gene(& thereby the mutant protein)
Recessive diseases: The strategy involves a suppl of the wild type / normal copy of the gene to supply the wild type protein
Drug development: Using knowledge from the human genome project and viral vectors and cell and animal models, the development of therapies for many human genetic disorders becomes a realistic aspiration. Knowledge of the underlying genetic basis of a condition enables the development of designer therapies targeted towards the cause of the disease as opposed to a somewhat random approach (serendipity) at times used to develop drugs in the past.
Inherited retinal disorders: Leber Congenital Amaurosis, (LCA) an autosomal recessive eye disorder. The RPE65 gene is one of the causes of LCA and also some other types of recessive eye diseases. The RPE65 gene encodes for an important enzyme involved in the regenerating light sensitive molecules in the retina.
Genetics has many applications: 1) Production of safer vaccines, recombinant