A Glance on Genetics I

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• A Glance on Genetics - I

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In this presentation

• Part 1 Findings in Classical Genetics
• Part 2 Carbohydrates
• Part 3 Nucleotides
• Part 4 Amino Acids

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Part1

• Findings in Classical Genetics

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Findings

• Children resemble their parents
• Genes come in pairs
• Genes do not blend
• Some genes are dominant whereas some are
  recessive
• Genetic inheritance follows rules
• All cells arise from pre-existing cells
• Sex cells have one set of chromosomes body cells
  have two
• Specialized chromosomes determine gender
• Chromosomes carry genes
• Genes get shuffled when chromosomes exchange
  pieces

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Findings

• Evolution begins with the inheritance of gene
  variations
• Mendelian genetics cannot fully explain human
  health and behaviour
• There are 44 autosomes and 2 sex chromosomes in
  human genome, for a total of 46
• Most of the disorders in human is due to
  non-disjunction associated with chromosome 21
• Higher cells incorporate an ancient chromosome
• Genes can be turned on and off
• Genes can be moved between species
• Different genes are active in different kinds of
  cells
• Master genes control basic body plans
• Development balances cell growth and death

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Findings

• A genome is an entire set of genes
• Living things share common genes

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HSV Virus
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Evolution levels

• Level 1
• Gases
• Level 2
• N-bases
• Sugars
• Amino acids
• Glycerin
• Fatty acids

• Level 3
• Fats, lipids
• Proteins
• Polysaccharides
• Nucleotides
• Nucleic acids
•  Level 4
• Energy sources
• Enzymes
• Construction materials
• Coenzymes
• Energy carriers
• DNA
• RNA

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• Cells that possess numerous intracellular
  compartments enclosed by membranes (called
  organelles) are called eukaryotic cells, for
  example, cells of animals, plants, fungi and
  protists. There are certain non-membranous
  organelles such as centrioles and ribosomes
• Cells that do not possess membrane bound
  organelles are called prokaryotic cells. Some
  cells do not even the chromosomes enclosed, for
  instance, bacteriaThe collection of various
  types of molecules in a cell is termed as the
  cellular pool
• Approximately, 93 percent of the cellular
  material is composed of carbon, hydrogen and
  oxygen. The non-metal elements nitrogen,
  phosphorus, chlorine and sulphur form about 2
  percent of the total material in the cell whereas
  iodine, fluorine, boron and selenium occur in
  traces. Less than 5 percent of the constituents
  comprise major metal elements such as calcium,
  potassium, sodium and magnesium. Traces of
  copper, cobalt, zinc, manganese, molybdenum, and
  chromium are found

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• Polymerization of a large number of small
  molecules gives rise to macromolecules such as
  proteins, nucleic acids and certain
  polysaccharides
• Proteins cannot be synthesized without DNA and
  DNA cannot be made without enzymes, which are
  proteins. This is a kind of chicken-and-egg
  dogma

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Flow of information to a cell

• Flow of genetic information Genetic information
  contained in DNA is transcribed into RNA, which
  is translated into specific proteins
• Flow of extrinsic information Molecules such as
  hormones pass information, coming from outside to
  the cell. Some of these enter the cell to
  influence its activities. Others bind on to the
  cell surface with certain molecules that serve as
  receptors. Such binding leads to significant
  changes in cellular activities. Studying the
  nature and action of such molecular receptors of
  cell membrane is an important line of modern
  research.

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Part2

• Carbohydrates

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Carbohydrates

• About 80 percent of the dry weight of plants is
  made of carbohydrates, which is produced due to
  photosynthesis
• General formula for carbohydrates is CnH2nOn.
• Carbohydrates are known as saccharides or
  compounds containing sugar, the simplest being
  monosaccharides, which cannot be hydrolysed still
  further
• Monosaccharides are composed of 3 to 7 carbon
  atoms viz., trioses (C3H6O3), tetroses (C4H8O4),
  pentoses (C5H10O5), hexoses (C6H12O6) and
  heptoses (C7H14O7)
• Hexoses and heptoses exists in both open chain
  and in ring forms

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Hexoses and heptoses exists in both open chain
and in ring forms
 
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• Glucose, fructose and galactose are hexoses.
  They are all white, crystalline, sweet-tasting
  substances extremely soluble in water.
• Ribose is a pentose and glyceraldehydes and
  dihydroxyacetone are trioses
• Deoxyribose that occurs in DNA is a pentose

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• Compound carbohydrates can be classified into
  three major groups
• Oligosacchrides (made of few molecules of
  monosaccharides) such as membranes
• Structural polysaccharides (composed of hundreds
  of simple sugar molecules such as cellulose and
  lignocellulose of plant wall
• Food-storage polysaccharides such as starch and
  glycogen
• Disaccharides are composed of two
  monosaccharides.
• A molecule of sucrose is formed from a molecule
  of glucose and one of fructose.
• Lactose or milk sugar is formed from one glucose
  molecule and one of galactose
• Maltose or malt sugar is formed from two
  molecules of glucose

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Hexokinase Glucose
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Part3

• Nucleotides

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Nucleotides

• Nucleotides contain carbon, hydrogen, oxygen,
  nitrogen and phosphorus
• Each nucleotide is made up of a cyclic
  nitrogenous base, a pentose and one to three
  phosphate groups
• The nitrogenous ring in nucleotides are either a
  purine or pyrimidine
• The pentose is either ribose or deoxyribose. The
  nucleotides are thus called ribonucleotides or
  deoxyribonucleotides
• Examples of ribonucleotides or deoxyribonucleotide
  s are adenylic acid (AMP) and deoxyadenylic acid
  (d AMP) respectively
• A combination of the nitrogenous base with the
  pentose sugar is known as a nucleoside. For
  instance, adenosine is a nucleoside made of
  adenine and ribose
• Ribonucleotides are the basic units of RNA and
  deoxyribonucleotides are basic units of DNA

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Nucleotides are mono-, di-, or tri-phosphates of
nucleoside. For example, adenylic acid or
adenosine monophosphate (AMP), adenosine
diphosphate (ADP) and adenosine triphosphate
(ATP) are all adenine nucleotides
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• Likewise, other purines and pyrimidines can also
  form higher nucleotides
• Sugars, amino acids and nucleotides polymerize to
  produce large molecules or macromolecules
• Most important macromolecules are the
  polysaccharides, proteins and nucleic acids,
  which have high molecular weights and may be
  branched or unbranched
• Starch, cellulose and glycogen are composed of a
  single type of monosaccharides while some other
  like agar are made up of more than one type of
  monosachharides

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Part4

• Amino Acids

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Amino Acids

• Proteins are the fundamental building blocks of
  life
• Enzymes are proteins that are molecular machines
  responsible for all the chemical transformations
  cells are capable of
• Those structure that are not made of proteins are
  produced by enzymes (which are proteins)
• A human contains proteins of the order of 100,000
  different proteins
• Proteins are of variable length and shape
• Proteins are mixed polymers of 20 different amino
  acids (or residues)

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The protein backbone unit and the 20 amino acid
side chains, shown with the three and one letter
abbreviations for each. Proline is an amino acid,
and its N and Ca backbone atoms are shown. Greek
letters ( a, b, g, d, e, z, h) identify the
distance (number of bonds) from the central ( a)
carbon atom. Ccarbon, Hhydrogen, Nnitrogen,
Ooxygen, Ssulphur atoms
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• Polymers of amino acids are also called peptides
  or polypeptides
• Polymers fold themselves to generate a shape
  characteristic of each different protein
• The shape of the protein along with different
  chemical properties of the 20 amino acids
  determine the function of the protein
• In theory, by knowing the sequence of a protein,
  it is possible to infer its function
• Small or simple molecular modules are called
  monomers whereas large or complex biological
  molecular modules are termed as polymers
• Many monomer molecules can be joined together to
  form a single and large macromolecule
• In both DNA and RNA, the linear polymers can form
  pair with one another
• The nucleotides Adenine (A) and Guanine (G) are
  called Purines whereas Cytosine (C) and Thymine
  (T) are called Pyrimidines

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Purines
Guanine
Adenine
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Pyrimidines
Cytosine
Uracil
Thymine
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A double-ringed purine is always bonded to a
single ringed pyrimidine. G pairs with C and A
pairs with T or U
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• Amino acids are small molecules made of carbon,
  hydrogen, oxygen and nitrogen, and in some cases
  also sulphur
• They are monocarboxylic or dicarboxylic acids
  bearing one or two amino groups
• The four valences of the a-carbon of an amino
  acid hold respectively an amino (NH2) group, a
  carboxyl (COOH) group, a hydrogen atom and a side
  chain
• The side chain may be polar or non-polar

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The activities of DNA Polymerase I on various
templates and primers
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• A free amino group is basic a free carboxyl
  group is acidic
• Lysine and arginine are basic amino acids since
  they carry two amino groups and one carboxyl
  group
• Glutamic acid (glutamate) and aspartic acid
  (aspartate) contain one amino and two carboxyl
  groups each and are classified as acidic amino
  acids
• Alanine, glycine, valine and phenylalanine are
  neutral amino acids as they contain one amino and
  one carboxyl group

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The basic chemical structure of an amino acid.
Carbon atoms are black, oxygen is dark grey,
nitrogen light gray, and hydrogen white.
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• Amino acid side chains differ in their
  physico-chemical features
• Some amino acids like to be exposed to water and
  hence called hydrophilic whereas the hydrophobic
  amino acids tend to avoid exposure to water
• Hydrophobic amino acids tend to occur in the
  interior of globular proteins whereas hydrophilic
  residues are found preferentially at the surface
  of the proteins

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Relationships between the physiochemical
properties of amino acids
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• The genetic code consists of 61 amino acid coding
  codons and three termination codons that start
  and stop the process of translation
• Features of individual amino acids also play a
  key role in protein secondary structure formation
• Proteins are macromolecules formed from a large
  number of amino acids. They are distinct from
  amino acids and small peptides in many properties

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• Charge, size, or flexibility in the backbone are
  only some of the other examples of amino acid
  parameters
• The parameters are measured on a numeric scale
  such that for every parameter there exists a
  table assigning a number to each amino acid
• Taking both parameters viz., physico-chemical and
  preferential occurrences together into account,
  more than 200 amino acid parameters have been
  published

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• An amino acid, tyrosine, is converted into the
  hormones thyroxin and adrenaline, as well as the
  skin pigment melanin
• Glycine is involved in the formation of heme and
  tryptophan in the formation of the vitamin
  nicotinamide as well as the plant hormone
  indole-3-acetic acid
• In trans-membrane proteins, the regions of the
  chain that span the membrane tend to be strongly
  hydrophobic

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• Successive amino acids can be linked by the
  formation of a peptide bond to form a linear
  chain of many amino acids
• When few amino acids are joined together, the
  molecule is called a peptide
• Glutamate is frequently found in ? helices,
  Valine has a preference for ? strands and Proline
  is known to be strongly avoided in helices

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• Many structural proteins contain amphipatic
  helices, which consist of hydrophobic, non-polar
  residues on one side of the helical cylinder and
  hydrophilic and polar residues on the other side,
  resulting in a hydrophobic moment. Such proteins
  aggregate with other hydrophobe surfaces and
  serve for example as pores or channels in the
  cell membrane
• Some amphipatic helices are arranged as
  inter-twined helices and are also called as
  coiled-coils or super-helices

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• Generally, the sequence of an alpha helix that
  participates in a coiled-coil region will display
  a periodicity with a repeated unit length of 7
  amino acids, which is called a heptad repeat
• Half of the 7 amino acids denoted by a through g,
  then position a and d are hydrophobic (define an
  apolar stripe) while there exist electrostatic
  interactions between residues at positions e and
  g. They form a parallel coiled-coil of alpha
  helices from two polypeptides chains holding them
  together