Molecular basis of inheritance

• A nitrogenous base is linked to the first carbon of pentose sugar through N-glycosidic linkage to form a nucleoside
• two nucleotides are linked through 3’—> 5’ phosphodiester linkage to form a dinucleotide
• the backbone in a polynucleotide chai is formed of sugar and phosphate
• the nitrogenous bases linked to sugar moiety project from the backbone
• Friedrich Miescher first identified DNA as an acidic substance present in the nucleus and named it as nuclein which was later named as nucleic acid by Altman
• Levene found that DNA contains phosphoric acid as well as deoxyribose sugar. He also found that four types of nucleotides are present in DNA
• The long polymer of deoxyribonucleotides is known as a DNA. It is made up of two polynucleotide chains.
• the negatively charged DNA is wrapped around the positively charged histone octamer to form structure called nucleosome.
• In prokaryotic cells such as E. coli, the DNA is held with some proteins in a region called as nucleoid
• in eukaryotes, there is a set of positively charged proteins called histones. These are rich in basic amino acid residues, lysines and arginines.
• the negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called nucleosome
• H1 is also known as linker histone
• nucleosomes are a the repeating unit of a structure called chromatin
• NHC : Non-Histone Chromosomal proteins
• In a nucleus some regions of chromatin are loosely packed and are called Euchromatin
• some regions chromosome is densely packed and are called heterochromatin
• FredErick Griffith carried out a series of experiments with Streptococcus pneumoniae
• DNase causes inhibition of transformation indicating that DNA caused transformation
• Transcription


  Process of copying genetic information from one strand into RNA
• The scheme for replication of DNA is termed as semi-conservative DNA replication.
• helicase unwinds DNA
• DNA polymerase replicates DNA to build new strands
• Primase makes primer which in turn shows where the DNA polymerase should go
• ligase helps bind DNA together
• Topoisomerase is an enzyme which alters the supercoiled form of a DNA molecule.
• SSB protein stabilises uncoiled DNA strand so that it cannot coil again
• the fragments in the lagging strand is called Okazaki strand
• mRNA - template for transcription
• tRNA - brings amino acids and reads genetic code
• rRNA - structural and catalytic role during translation
• central dogma states that genetic information flows from DNA to RNA and then to proteins
• the long polymer of deoxyribonucleic acid is known as DNA which is made of two polynucleotide chains
• a molecule of DNA is wrapped around proteins to form a single chromatin thread
• in E. coli, DNA being negatively charged is held with some proteins in a region called as nucleotide
• eukaryotes have positively charged proteins called histones that wrap around DNA
• H1 is called linker histone
• The packaging of chromatin at a higher level requires additional set of proteins called Non-Histone Chromosomal protein
• the negatively charged DNA is wrapped around the positively charged histone octamer to form a structure called nucleosome.
• nucleosomes are repeating unit of a structure called chromatin
• the backbone of a polynucleotide chain is formed of sugar and phosphates