RBSE Class 12 Biology Notes Chapter 6 Molecular Basis of Inheritance

These comprehensive RBSE Class 12 Biology Notes Chapter 6 Molecular Basis of Inheritance will give a brief overview of all the concepts.

RBSE Class 12 Biology Chapter 6 Notes Molecular Basis of Inheritance

→ Over the years after Mendel, the nature of the genetic material was investigated, it resulted in the realisation that DNA is the genetic material in majority of organisms.

→ There are two types of nucleic acid Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA). Nucleic acids are polymers of nucleotides.

→ DNA acts as a genetic material in most organisms, whereas RNA acts as genetic material in some viruses.

→ A nucleotide has three parts: a nitrogen base, a pentose sugar (Deoxyribose in DNA and ribose in RNA) and phosphate group.

→ Several nucleotides join to form a polynucleotide chain. The backbone in a polynucleotide chain is formed of sugar and phosphates. The nitrogenous bases linked to sugar moiety project from the backbone.

→ DNA is a long polymer of deoxyribonucleotides. It is made up ‘of two polynucleotide chains. These chains are antiparallel to each other i.e., 5' →  3' for one, 3' →  5' for another.

→ The structural proteins are responsible for packaging the DNA so that it can fit into small space of the cell (in nucleus). Polynuclucleotide chain having nucleosome (called chromatin) is highly condensed to form chromosomes.

→ Frederick Griffith carried out a series of experiments with Streptoccocus pneu moniae to demonstrate that DNA is genetic material.

→ Avery, McLeod and McCarty gave unequal proof that DNA is the genetic material.

→ RNA is also a genetic material in plant viruses and some animal viruses.

→ There one three types of RNA: mRNA, tRNA and rRNA.

→ Francis Crick proposed the central dogma in molecular biology which states that genetic information flows from DNA to RNA and then to proteins:
DNA →  RNA →  Protein.

→ The scheme for replication of DNA is termed as semi-conservative DNA replication. It was proposed by Watson and Crick (1953).

→ Mathew Mesalson and Franklin Stahl performed experiments to prove semi.conservative mode of DNA replication in 1958.

→ Transcription is the process of copying genetic information from one strand of the DNA into RNA.

→ A gene can be defined as the functional unit of inheritance. Genes are located on the chromosomes.

→ Genetic code is a sequence of three nucleotides present on ,nRNA, which codes for a specific amino acid during translation.

→ The sudden inheritable change in the genetic material is defined as Mutation. They can be paint mutation, frameshift mutation or silent
mutation.

→ The process of polymerisation of amino acids to form a polypeptide is called translation.

→ In prokaryotes, gene expression is regulated by the rate of initiation of transcription. In eukaryotes, regulation is achieved at four levels.

→ Human genome project is a mega project. It was closely associated with rapid development of a new area in biology called bioinfermatics.

→ DNA fingerprinting is a quick way to compare the DNA sequences of any two individuals.

→ Gene: Ultimate unit of recombination, mutation and self reproduction.

→ Genome: Total number of genes present on haploid set of chromosomes represents one genome.

→ Genetic Material:    The substance that stares information about structure, function and development of various characteristics of organisms.

→ Bacteriophage: The virus which infects bacteria is called bacteriophage.

→ Capsid: Outer proteinaceous sheath of virus inside it genetic material is present.

→ Plasmid: Extra nuclear DNA found in bacterial cells. Nucleoside: The combination of a base and pentose sugar.

→ Nucleotide: The combination of a base, a pentose sugar and a phosphate group. A monomer of polynucleotide chain.

→ Cistron: A unit function i. e., segment of DNA which determines a single polypeptide chain.

→ Jumping gene: The genes which show shuffling from one location to another are called jumping gene.

→ Muton: The smallest unit of gene capable of mutation. Lysogen: A strain of bacteria carrying prophase. Anticodon: A triplet bases present on iRNA, complementing with mRNA codon is called anticodon. Codon: Triplet of bases on mRNA coding for one amino acid.

→ Rho-factor: The factor which is required for termination of RNA synthesis at some sites.

→ Replication: The process of producing two identical replicas of DNA from one original DNA molecule. Transcription: It is the process of copying genetic information from one strand of the DNA into RNA. Translation: It is the process of polymerisation of amino acids to form a polypeptide.

→ Introns: A segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.

→ Exons: A segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.

→ Inducer: An effector molecule responsible for induction of enzyme synthesis at recognition sites, to prevent self cleavage by a modified enzyme that recognises the sites and methylates specific nucleotides at each site.

→ Ribozyme: Ribosomse that serves as an enzyme.

→ Transposons: A chromosomal segment that can undergo transposition, especially a segment of bacterial DNA that can be translocated as a whole between chromosomal, phage and plasmid DNA in the absence of a complementary sequence in the host DNA.