Students can go through AP Inter 2nd Year Botany Notes 10th Lesson Molecular Basis of Inheritance will help students in revising the entire concepts quickly.
AP Inter 2nd Year Botany Notes 10th Lesson Molecular Basis of Inheritance
→ Deoxyribonucleic acid (DNA) and ribo nucleic acid (RNA) are the two types of nucleic acids found in living systems.
→ DNA acts as the genetic material in most of the organisms.
→ RNA acts as the genetic material in most of the organisms.
→ RNA acts as a genetic material in some viruses but mostly it functions as adapter, structural and in some cases as a catalytic molecule.
→ The length of DNA is usually defined in terms of number of nucleotides or base pairs present in it.
→ Bacteriophase Φ × 174 has 5386 nucleotides.
→ Bacteriophase lambda has 48502 base pairs.
→ E.Coli cell has 4.6 × 106 base pairs.
→ Haploid content of human DNA is 3.3 × 109 base pairs.
→ A nucleotide has three components, a nitrogeneous base, a pentose sugar, and a phosphate group.
→ There are two types of nitrogeneous bases – Purines (Adenmine and Guanine) Pyramidines (Thymine and Cytosine)
→ A combines with T by two hydrogen bonds like that G combines with C by three hydrogen bonds.
→ DNA, as an acidic substance present in nucleus was first identified by Friedrich Meischer in 1869 and named it as Nuclein.
→ Watson and Crick framed a double helical model of DNA.
→ The DNA of prokayotes in circular and lacks chromatin organisation. It is referred to as genophore.
→ In Eukaryotes, the negatively charged DNA is wrapped around the positively charged histone octamer to form a Beads-on-string called Nucleosomes.
→ The chromatin which stains light and loosely packed is called Euchromatin.
→ The chromatin which stains dark and densely packed is called Hetero chrematin.
→ Frederick Griffith in 1928 worked on streptococcus pneumoniael witnessed a miraculoes transformation in the bacteria.
→ Avery, Macleod and Mccarty concluded that DNA is the heriditary material.
→ The unequivocal proof that DNA is the Genetic material came from Hershv and change They worked with Bacteriophages.
→ RNA is the genetic material in Tobacco mosaic viruses, QB bacteriophage HIV etc.,
→ RNA is unstable and mutates at a faster rate.
→ DNA is more stable and is preferred for storage of genetic information.
→ Catalytic RNA or RNA enzymes are known as Ribozymes.
→ DNA replicates in a semi conservatively method. It was shown first in
→ E.coli by meselson and stahl.
→ In DNA Replication, the discontinuously synthesised fragments known as Okazaki fragments are later joined by the enzyme DNA ligage.
→ The region of E.coli DNA, where the replication originates is called origin of replication (ori).
→ The process of copying genetic information from one stand of DNA to RNA is termed transcription.
→ In Bacteria, m-RNA, t-RNA and r-RNA are present.
→ Three RNA polymerages are present in the nucleus.
→ The codon is Triplet. 61 codons code for amino acids and 3 codons do not code for any aminoacids called stop codons,
→ AUG codes for methionine and also acts as the Initiator coden.
→ Molecular biology deals with study of Macro molecules and their mechanisms in living organisms such as gene replication, mutation and expression.
→ Molecular basis of inheritance for most of the organisms is due to 2 nucleic acids DNA , RNA.
→ Nucleic acids are long polymers of nucleotides.
→ DNA stores the genetic information where as RNA helps in expression of information.
→ DNA is chemically and structurally more stable and it is better genetic material than RNA.
→ DNA has double stranded helical structure and RNA has single stranded helix structure.
→ DNA undergoes self-replication but RNA does not undergo self-replication.
→ DNA is written in 3 letter words. Each of such ‘3 letter word’ is called a codon.
→ Each codon encodes for one of the 20 amino acids used in the synthesis of proteins.
→ Genetic code is a set of instructions that direct the translation of DNA into 20 amino acids.
→ Components of nucleotide: Nitrogenbase, pentose sugar and phosphate molecule.
→ Components of transcription unit: (i) A promoter (ii) The structural gene (iii) A Terminator
→ Exons: These are coding sequences . They appear in mature or processed RNA.
→ Introns: These are non-coding sequences. They do not appear in mature or processed RNA.
→ Capping: Adding of an unusual nucleotide (methyl guanosine triphosphate) to the 5′-end of hnRNA is called Capping.
→ Tailing: Adding of adenylate residues (200-300) to the 3′-end in a template is called tailing.
→ Nueleosome is a bead like structure of chromosomes.
→ Spliceosomes are not found in cells of bacteria. [NEET-2017]
→ The association of histone H with a nucleosome indicates that the DNA is condensed into a chromatin fibre. [NEET-2017]
→ The final proof for DNA as the genetic material came from the experiments of Hershey and Chase. [NEET-2017]
→ The equivalent of a structural gene is cistron. [NEET-2016]
→ A complex of ribosomes attached to a single strand of RNA is known as polysome. [2016]
→ AUG is the starter codon. [NEET-2016]
→ The movement of a gene from one linkage group to another is called translocation. [2015]
→ Balbiani rings are sites of Chargalfs rule. [NEET-2015]
→ The first phase of translation is aminocylation of tRNA. [NEET-2020]