biofunda

 Genetic code  It is combination of three consecutive Nitrigenous bases which code for amino acids.  Properties of genetic code  It is triplet  . The three nucleotides of mRNA which code for one amino acid represent codon. Complementary matching triplet of tRNA form the anticodon.    The codon which initiates protein synthesis is called as initiation codon  i.e.Methionine (AUG) and valine (GUG).  Some of codon do not code for any amino acid, such codon are known as non-sense codon i.e. UGA(Opal),UAA(Ochre) and UAG (amber) . They signal termination of polypeptide chain hence also called as termination or stop codons. Hence out of 64 codons 61 code for amino acids.  The code is degenerate . For a particular amino acids more than one codon can be used. One amino acid often has more than one code triplet e.g. Phenylalanine has two codon i.e. UUU and UUC. Arginin, similarly has six codon.  The genetic code is universal . Given codon in D...

  Replication is commonly known as self duplication.  But why DNA replicates? 🤔🤔 DNA transfer inherited characters form generation to next generation. So DNA has to produce it's duplicate copy.  Replication is autocatalytic function of DNA. A simple mechanism of replication was proposed by Watson and Crick ,  on the basis of double helical structure of DNA. To know more about structure and  function of DNA click here ( https://singhsardarni.blogspot.com/2020/09/dna-structue-and-functions.html ) The method of DNA replication is described as semi - conservative method. In this method ,the two strands will act as template strands for synthesis of new complementary strands. After replication, new DNA will have one daughter  strand and one parental strand . But where is the evidence ?  DNA replicates semi conservatively was proved by Meselson and Stahl in 1958. They performed the following experiment with E . Coli .  They grew E. Coli in medi...

Satellite DNA (Repetitive DNA)   It is observed that after Denaturation(for more details click here https://singhsardarni.blogspot.com/2020/09/dna-structue-and-functions.html ), DNA fails to come back into original form easily. This may be due to two reasons : They are degraded molecules from heterogeneous populations. They are of high molecular weight.  However, Britten noticed that DNA can broken into small fragments. It gave conclusion that certain short sequences of bases are repeated hundreds of times in DNA .Such type of DNAs are known as repetitive DNA.  Such repetitive form of DNA observed in chromosome near to centromere.  Sometimes, repeating sequences of DNA may be similar to that of rest of DNA.  This type of DNA can be easily separated out by process of ultracentrifugation.  Prokaryotic DNA doesn't bear repetitive DNA sequences. Except yeast repetitive DNA has been observed in all eukaryotes. In human beings 30% of DNA is repetitive which ...

 Physical Properties DNA is usually double stranded.  Molecular configuration of DNA is three dimensional(3D). It's diameter is 2nm. Number of bases in one turn of DNA are 10. Angle of one complete turn is 360 degree.  Length of H-bond is near about3 angstrom.  Diameter of base pair between two stands is about 11 angstrom . Distance between two adjacent bases about 3.4 angstrom. Distance between two  complete turn is 34 angstrom.  Nitrogenous bases are A ,T, G, C.   Nitrogenous composition is always A\T =1 and G / C =1.  Purines and pyrimidines are in equal ratio . DNA behaves like polyelectrolyte because of phosphate group that lies on outer surface of DNA . Size of DNA varies. For example DNA of phage T2 bears 2 into 10 raise to power 5 pairs of nucleotides with molecular weight of 130 million. In eukaryotes DNA is always associated with histones which are basic in nature and positively charged. DNA molecules are very large and can be ...

  Deoxyribose nucleotide acid is polymer of deoxyribonucleotide . Each deoxyribonucleotide is made up of Ribose sugar , phosphate , and Nitrigenous base .  Sugar: DNA consist deoxyribose* sugar . Nitrigenous Base : It is of two types.  Purines : Adenine (A), Guanine (G) are purines,9_membraned double ring structure having N at 1,3,7,9 position  Add caption Pyrimidines : Thymime (T) ,Cytosine (C)  are Pyrimidines, 6_memberaned single ring structure having N at 1,3 position.  Bonding in DNA  There are two types of binding present in DNA i .e. Hydrogen bonding and covalent bonding.  Hydrogen bonding is present between nitrogenous bases. Adenine joined by  double bond with Thymime . Guanine joined with cytosine by Triple bond.  Covalent bonding :  Phosphodiester bond is formed between 5'phoshphate group of one  nucleotide with 3'OH of another nucleotide.  Bond between nitrogenous base and sugar is known as glycosidic ...

 DNA is genetic material in all living beings except few plant viruses. But why ? 🤔 Properties of genetic material  It must be Chemically   and structurally stable . It can produce it's replica .  It should provide scope for mutation that is required for evolution.  It should be able to express itself in the form of ' Mendelian characters . ' How DNA fulfill this criteria? Mendel believed that factor /genes contain the information which is required to express particular traits in successive  generations.As DNA consist genes and passes the heredity characters from one generation to next generation. So it fulfill the Mendelians character criteria.  Due to condition of producing replica, proteins fail to fulfill the criteria. Whereas DNA and RNA fulfills the criteria.  Both DNA and RNA are able to mutate. Because of presence of 2'-OH group (present at every nucleotide in RNA)  makes RNA labile and easily degrade. Due to this Unstabil...

 Nucleic acid is biopolymer,essensial for all living beings. They were first reported by Friedrich Miescher (1871) in nuclei of pus cell. He named them nucleic. They can be found in both nucleus and cytoplasm . Altman renamed nuclein and called them Nucleic acid . Nucleoprotein  Nucleic acid along with basic proteins make nucleoprotein which is sub unit of chromosome.   In nucleoprotein, nucleic acid is prosthetic group and protein part consist of protamine and histone (basic nature).  They are very complex and high molecular proteins.  Composition  Basic structure of nucleic acid consist of Sugar, nitrogenous base *(adenine,guanine,thymine,cytosine,uracil) and phosphorus. This combined structure of sugar, phosphorus and nitrogenous base is known as nucleotide.   DNA is made up of deoxyribonucleotides  which is further made up of Deoxyribose sugar, phosphorus, and nitrogenenous bases (adenine,thymine guanine, cytosine) RNA is made up of ribo...