Yogy's biology

04 Molecular Basis of Inheritance - part 14 - DNA Fingerprinting DNA Fingerprinting:  Genes present on chromosomes are responsible for determining characters of the organism as well as for inheritance of characters.  Due to  recombination of paternal and maternal genes,  we differ from our parents.  Differences also arise due to  infrequent mutations  that occur during gamete formation (cell division).  Due to all these factors, every individual has its  unique genetic make-up , which may be called its  Fingerprint.  The technique developed to identify a person with the help of DNA restriction analysis, is known as  DNA profiling or DNA fingerprinting.  The technique of finger printing was first given by British geneticist,  Dr. Alec Jeffreys  in 1984. DNA fingerprinting technique is based on identification of nucleotide sequence  present in this wonder molecule.  About  99.9%  of nucleotide s...

04 Molecular Basis of Inheritance - part 13 - Human Genome Project Human Genome Project :  Initiated in  1990  under the International administration of the Human Genome Organization (HUGO).  Co-ordinated by the  US department of Energy and National institute of health.  Additional contributors included universities across the United States and international partners in the  United Kingdom, France, Germany, Japan, India and China.  The Human Genome Project formally began in 1990 and was  completed in 2003. Is a multinational research project to determine the genomic structure of humans.  The main aims of project are ­- Mapping the entire human genome at the level of nucleotide sequences.  To store the information collected from the project in databases.  To develop tools and techniques for analysis of the data. Transfer of the related technologies to the private sectors, such as industries.  Taking care of the legal, ethic...

04 Molecular Basis of Inheritance - part 12 - Genomics Genomics:  The term Genome (introduced by  H.Winkler  in 1920) is the  total genetic constitution of an organism.  Alternatively, it is a complete copy of genetic information (DNA) or one complete set of chromosomes (monoploid or haploid) of an organism.  The term Genomics (term coined by  T.H. Roderick  in 1986) is  the study of genomes through analysis, sequencing and mapping of genes along with the study of their functions. The sequencing of  yeast, Drosophila and mouse genome was done in order to facilitate comparative studies between humans and other organisms commonly used for genetic studies, in laboratory.  Several additional genomes are now either actively being sequenced or strongly considered for sequencing.  These include several  microbes, bee, tomato and other crops .  Genomics study may be classified into two types:  Structural genomics Functio...

04 Molecular Basis of Inheritance - part 11 - Operon concept - Lac operon Operon concept :  It is a  transcriptional control mechanism of gene regulation.  Francois Jacob and Jacques Monod  (1961) explained that metabolic pathways are regulated as a unit. For example in E.coli, when lactose sugar is provided to the culture medium, cell induces production of three enzymes necessary for digestion of lactose.  The enzymes are : b-galactosidase  : Digests lactose into galactose and glucose. b-galactoside permease  : Permits lactose molecules to enter into the cell. Transacetylase (b-Galactoside acetyltransferease)  : Transfers an acetyl group from acetyl CO-A to galactoside.  Synthesis of these three enzymes, is controlled by a  long segment of DNA  known as  Operon.  It consists of an  operator site O  and  three structural genes Z, Y and A  . The action of structural genes is regulated by operator site wi...

04 Molecular Basis of Inheritance - part 10 - Regulation of gene expression Regulation of gene expression:  It is the multistep process by which  a gene is regulated and its product is synthesized.  Thus, gene expression results in the formation of a Polypeptide.  Gene expression process is regulated at different levels.  In eukaryotes, the regulation can be at different levels like- Transcriptional level (formation of primary transcript)  Processing level ( regulation of splicing)  Transport of m-RNA from nucleus to the cytoplasm.  Translational level . Genes of a cell are expressed to perform different functions. For eg. An enzyme  beta galactosidase is synthesised by E-coli.  It is used for  hydrolysis of lactose into galactose and glucose. If E.coli bacteria do not have lactose in the surrounding medium as a source of energy, then enzyme  b-galactosidase  is not synthesised.  So, it is the metabolic or physiologic...

04 Molecular Basis of Inheritance - part 09 - Translation - protein synthesis Translation - protein synthesis :  Translation is  the mechanism in which codons of mRNA are translated and specific amino acids in a sequence form a polypeptide on ribosomes.  All types of proteins are synthesised by the cell, within itself (i.e. intracellularly).  Process of translation requires  amino acids, mRNA, tRNA, ribosomes, ATP, Mg++ ions, enzymes, elongation, translocation and release factors.  Amino acids form raw material for protein synthesis.  About 20 different types of amino acids are known to form proteins. These are available in the cytoplasm.  DNA controls synthesis of proteins having amino acids in specific sequence. This control is possible through  transcription of m-RNA.  Genetic code is specific for particular amino acid.  RNAs serve as intermediate molecules between DNA and protein.   Ribosomes  serve as  site ...

04 Molecular Basis of Inheritance - part 08 - Mutations and Genetic Code + t-RNA- the adapter molecule Mutations and Genetic Code:  Mutation is a phenomenon in which  sudden change in the DNA sequence  takes place. It results in the  change of genotype  (i.e. character).  Along with recombination, mutation is raw material for evolution as it also results in variations.  During mutation, possibility of loss (deletion) or gain (insertion/ duplication) of a segment of DNA results in alteration in the chromosome.  Mutation can also occur  due to change in a single base pair of DNA . This is known as  point mutation.  Eg.  Sickle cell anaemia . Deletion or insertion of base pairs of DNA causes  frame ­ shift mutations or deletion mutation.  Insertion or deletion of one or two bases changes the reading frame from the point of insertion or deletion.  Insertion or deletion of  three or multiples of three bases ...

04 Molecular Basis of Inheritance - part 07 - Characterestic of Genetic code: Characterestic of Genetic code: Genetic code of DNA has certain  fundamental characteristics ­  i. Genetic code is a triplet code:  Sequence of three consecutive bases constitute codon, which specifies one particular amino acid.  Base sequence in a codon is always in  5'- 3' direction.  In every living organism genetic code is a triplet code.  ii. Genetic code has distinct polarity :  Genetic code shows  definite polarity i.e. direction . It, therefore, is always read in 5' - 3' direction and not in 3' 5' direction.  Otherwise message will change e.g. 5' AUG 3'.  iii. Genetic code is non-overlapping :  Code is non overlapping i.e. each single base is a part of only one codon. Adjacent codons do not overlap.  If non-overlapping, then with 6 consequtive bases only two amino acid molecules will be in the chain Had it been overlapping type, with...