The blueprint of life; from DNA to Protein

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The blueprint of life from DNA to Protein

• Biology 261
• Medgar Evers College
• Prof. Santos

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• DNA, the substance of inheritance
• Is the most celebrated molecule of our time
• Hereditary information
• Is encoded in the chemical language of DNA and
  reproduced in all the cells of your body
• It is the DNA program
• That directs the development of many different
  types of traits

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DNA

• The Components and Structure of DNA
• DNA is made up of nucleotides.
• A nucleotide is a monomer of nucleic acids made
  up of
• Deoxyribose 5-carbon Sugar
• Phosphate Group
• Nitrogenous Base

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• There are four kinds of bases in in DNA
• adenine
• guanine
• cytosine
• thymine

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Chargaffs rule

• Chargaff's Rules
• Erwin Chargaff discovered that
• The percentages of guanine G and cytosine C
  bases are almost equal in any sample of DNA.
• The percentages of adenine A and thymine T
  bases are almost equal in any sample of DNA.

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DNA Double Helix
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• There are 2 hydrogen bonds between adenine and
  thymine and three hydrogen bonds between cytosine
  and guanine.

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DNA to RNA to Protein connection
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Protein synthesis

• 3 steps
• 1- transcription
• 2- RNA processing
• 3- translation

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transcription

• 3 steps
• 1- initiation
• 2- elongation
• 3- termination

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Transcription

• Copying the genetic code directly from DNA.
• We make a single strand of messenger RNA.
• We begin initiation by unwinding the double
  stranded DNA and copying only one of the strands.
  The strand that is copied is called the nonsense
  strand. It serves as a template for the
  production of messenger RNA.

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• Transcription begins when an enzyme called RNA
  polymerase binds to a special region of the DNA
  called promoter sequence. Unlike DNA polymerase,
  RNA polymerase doesnt need a primer.
• RNA polymerase brings free floating RNA
  nucleotides to the nonsense strand.

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• The immediate product of this transcription is a
  resultant initial RNA transcript, which contains
  a sequence of nucleotides that is identical to
  the that of the sense strand. The exception to
  this is that uracil is used for nucleotide
  sequencing of RNA molecules rather than thymine.

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Role of transcription factors

• Transcription factors are proteins that aid in
  the process of transcription. They can be
  involved in promoting or blocking (repressing)
  the action of RNA Polymerase.

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• Guanine and cytosine pair up.
• But, there is no thymine in RNA. Another base
  called Uracil pairs up with adenine.
• The messenger RNA strand will continue to
  elongate until it reaches a termination point.

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RNA processing

• The pre messenger RNA made must be modified
  before it can leave the nucleus and direct the
  production of proteins.
• 3 steps
• 1- removal of introns
• 2- addition of cap at 5 end
• 3- poly A tail at 3 end

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• The coding regions are called exons and the
  non-coding regions are called introns.
• The introns are removed by an enzyme-RNA complex
  known as the spliceosome.
• A tail of adenine bases is added to the 3 prime
  end and a modified guanine nucleotide is added to
  the 5 prime end.

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• Once the messenger RNA has been processed, it is
  ready to leave the nucleus and bind to a
  ribosome.
• The mature messenger RNA carries the message from
  DNA in the forms of codons.
• A codon is a group of 3 bases that correspond to
  one of the 20 amino acids.

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• There are 64 possible codons and only 20 amino
  acids. There is redundancy with some of the amino
  acids!
• The initial codon is AUG or methionine and there
  are three stop codons, UAA, UGA and UAG.

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Translation

• The messenger RNA attaches to the ribosome and
  the message in the form of codons is translated
  and the appropriate amino acid is put in place.
• A molecule of RNA called transfer RNA brings
  along the amino acid. It resembles a four leaf
  clover.
• On the top is the amino acid and on the bottom is
  a sequence known as the anti codon.

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• The anticodon pairs up with the codon. This
  allows the amino acids to put placed in the
  correct sequence or order.

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