Chromosomes: Thread like structures inside nucleus at time of cell division. Walther Felming => 1882 => salamander larvae => in all Eukaryotes. Penicillium fungus => 1 pair of chromosome = 2. Mosquito = six pair of chromosome. Mouse = 40 chromosome. Honeybee = 32 chromosome. Corn = 20 chromosome. Sugarcane = 80 chromosome. Frog = 26 chromosome. Human = 46 chromosome.
Two chromatids, contain thousand of genes a Centromere ( primary constriction and secondary constriction).
Tyes of chromosome:
Karyotype: Array of metaphase chromosomes that an individual possesess collection of chromosomes.
Telocentric: Centromere at end I - shaped.
Acrocentric: Centromere close to end end. one arm is shorts, than other V - shaped.
Sub- metroentric: Centromere near middle P and Q arms => unequal length => L- shaped.
Metacentric: Equal chromosome arm P and q. centromere => midway. X - Shaped, Shape of chromosome at anaphase => i,j,v.
Composition: DNA 40 % and protein 60 % and some RNA => RNA synthesis sites long, double stranded, unbroken.
Human chromosome = 140 million (1.4X10⁸) nucleotide in DNA. Strand of DNA = in straight line = 5cm long.
Nucleosome: Every 200 nucleotides, DNA coiled around core 8 histone proteins => complex => nucleosome.
Histone: Positive charged, DNA => negative due to phosphate. Abundance of basic amino acid => argine and lysin.
Supwrcoils: string of nucleosome wraps into higher order.
Heterochromatin: Highly condensed portion of chromatin. Some portions permanently condensed => Their DNA never expressed.
Euchromatin: Remaing chromosome => non-condensed. Condensed only during cell division. Compact when packing helps in movement of chromosome. Open configuration => gene expressed.
Chromosomal Theory of Inheritance:
Karl correns => 1900 => central role of chromosome in heredity. First formulated by walter sutton => 1902.
Sutton Theory:
Reproduction => union of two gamete cells => egg and sperm. Sperm => little cytoplasm. Hereditary material resides => in nucleus of gametes diploid cell => two copies of each pair of have one homologous chromosome, gamete. Thomas hunt Morgan => fruitfly Dorsophilla discovered mutant male eye recessive. eyes were white instead of red => normal.
DNA as hereditary material:
Hereditary nature of DNA. Frederick Grifth => DNA hereditary not protein.
1. Infected mice with virupert strain of S - phenomenia polysaccharide coat. Mice died at blood poisoning.
2. Infected simila - mice with mutant. mice showed no illness.
Polysaccharide coat => necessary for virulence. Normal pathogenic form => S form => smooth clonies in dish.
Mutant form => R form => rough colonies.
Transformation:
Transfer of genetic material from one cell to another => alter genetic make up of recipient cells.
1. Live pathogenic strain of S pheumonia => Mice die.
2. Live non - pathogenic strain of S pheumonia => Mice live.
3. Hear killed pathogenic strain of S pheumonia => Mice live.
4. Mixture of heat killed pathogen and live non - pathogenic strain => Mice die => blood contain live pathogenic strain S phenomena.
RNa digestiy enzyme did not effect activity but DNA digestiy enzyme effected the transforming T² phase => DNA and protein.
Transforming principle => Osweld Avery and Colin - Macleod.
Hershey and chase experiment and Maclyn Mecarty. Further evidence => Experimented bacteriophage. Used radiosonde.
Labellel viruses:
1: Viruses labelled with P³² isotope.
2: Viruses labelled with S³⁵ medium.
When they infect bacteria => bacterial cells are agitated to remove protein coats. S³⁵ label was removed from bacteria but P³² transferred nts interior of bacteria.
Experiment Specified thst new generation of virus of was DNA not protein.
Chemical nature of DNA:
Frederick Meicscler =>1860 => discovered DNA four years after mendles wort white => white substance of human cell.
Deoxyribose associated white substance from nuclei and fish sperm.
RNA => H atom => to C atom.
RNA => OH atom => to C atom.
1920 => P.A levene => basic structure of nucleic acid outside DNA.
DNA => main components:
• P⁶⁴ group.
• Five carbon sugars
• Nitrogen contain basis inside DNA molecule.
DNA and RNA => repeating units => nucleotides => in nucleotide => Nitrogen bases is attached to C¹ of pentose sugar to C⁵ of pentoses sugar 5 phosphate and 3 hydroxyl group.
Phosphate group => OH group => C³ allow DNA and RNA to form long chains of nucleotide phosphate group of one nucleotide ans OH of another.
Dehydration synthesis: Releasing H²O molecule forming covalent bond that links two groups => Phosphodiester bond P-O-C.
Phosphate group is linked to two sugar by ester (P-O-C) bonds. Two unit polymer resulting from this has free 5 phosphate group at 1 end 2 free 3 OH at other, So that it can link to other nucleotides.
Many thousand of nucleotides joined together in long chain. Linear strands of DNA or RNA will always have free 5 phosphate group at 1 end 2 free 3 OH at other.
DNA Replication: Watson - crick suggested basis for copying genetic information is complementary. Semi - conservation and one old new groove Major. Unzip molecule => we need only to assemble appreciate complementary Minor groove. Nucleotides on exposed single strands to form => two daughter molecule. Sequence of original duplex conserved after one round of replication.
Meselson - stable Experiment:
Three hypothesis of DNA replication in 1958. Grew bacteria in a medium containing heavy isotope of nitrogen N¹⁵ => incorporated in bases of bacterial DNA.
After several generation later => bacterial N¹⁵ DNA denser man N¹⁴ medium bacteria.
Then N¹⁴ medium bacteria transferred to N¹⁴ medium collected DNA at various intervals.
Replication process:
DNA replication => begins at one or more sites on DNA molecules. Where there is a specific sequence of nucleotides.
DNA polymerase 111 begins a complex process. Addition of nucleotides to growing complementary strand of DNA. There are three polymera one two three phase.
One gene one Polypeptide:
Arginine biosynthesis pathway isolation => mutant strain => mutation was always located on one of few chromosomal sites.
Each gene encodes => structure of one enzyme.One gene => one enzyme hypothesis. Many enzyme => cause and multiple proteins / polypeptide subunits => each encoded => one gene => one Polypeptide by separate gene. Enzymes => Catalyze => synthesis of all parts of organisms. Enzymes => assembly of nucleic acidd, proteins, carbohydrates and lipids. By encoding the structure of enzyme and other proteins. DNA specifies the structure of enzyme itself.
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