RNA

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RNA

• Ribonucleic Acid

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Ribonucleic Acid (RNA)

• RNA is much more abundant than DNA
• There are several important differences between
  RNA and DNA
• - the pentose sugar in RNA is ribose, in DNA
  its deoxyribose
• - in RNA, uracil replaces the base thymine (U
  pairs with A)
• - RNA is single stranded while DNA is double
  stranded
• - RNA molecules are much smaller than DNA
  molecules)

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Structure of RNA

• Single stranded
• Ribose Sugar
• 5 carbon sugar
• Phosphate group
• Adenine, Uracil, Cytosine, Guanine

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Types of RNA

• Three main types
• Messenger RNA (mRNA) transfers DNA code to
  ribosomes for translation.
• Transfer RNA (tRNA) brings amino acids to
  ribosomes for protein synthesis.
• Ribosomal RNA (rRNA) Ribosomes are made of rRNA
  and protein.

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Transcription

• RNA molecules are produced by copying part of the
  nucleotide sequence of DNA into complementary
  sequence in RNA, a process called transcription.
• During transcription, RNA polymerase binds to DNA
  and separates the DNA strands. RNA polymerase
  then uses one strand of DNA as a template from
  which nucleotides are assembled into a strand of
  mRNA.

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mRNA
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How Does it Work?

• RNA Polymerase looks for a region on the DNA
  known as a promoter, where it binds and begins
  transcription.
• RNA strands are then edited. Some parts are
  removed (introns) - which are not expressed and
  other that are left are called exons or expressed
  genes.

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The Genetic Code

• This is the language of mRNA.
• Based on the 4 bases of mRNA.
• Words are 3 RNA sequences called codons.
• The strand aaacguucgccc would be separated as
  aaa-cgu-ucg-ccc the amino acids would then be
  Lysine Arginine Serine - Proline

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Genetic Codes
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Translation

• During translation, the cell uses information
  from messenger RNA to produce proteins.
• A Transcription occurs in nucleus.
• B mRNA moves to the cytoplasm then to the
  ribosomes. tRNA read the mRNA and obtain the
  amino acid coded for.
• C Ribosomes attach amino acids together forming
  a polypeptide chain.
• D Polypeptide chain keeps growing until a stop
  codon is reached.

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Protein Synthesis

• The two main processes involved in protein
  synthesis are
• - the formation of mRNA from DNA (transcription)
• - the conversion by tRNA to protein at the
  ribosome (translation)
• Transcription takes place in the nucleus, while
  translation takes place in the cytoplasm
• Genetic information is transcribed to form mRNA
  much the same way it is replicated during cell
  division

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Translation to Protein
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Mutations

• Gene mutations result from changes in a single
  gene. Chromosomal mutations involve changes
  whole chromosomes.

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Gene Mutation

• Point Mutation Affect one nucleotide thus
  occurring at a single point on the gene. Usually
  one nucleotide is substituted for another
  nucleotide.
• Frameshift Mutation Inserting an extra
  nucleotide or deleting a nucleotide causes the
  entire code to shift.

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Gene Mutation
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Chromosomal Mutations

• Deletion Part of a chromosome is deleted
• Duplication part of a chromosome is duplicated
• Inversion chromosome twists and inverts the
  code.
• Translocation Genetic information is traded
  between nonhomologous chromosomes.

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Chromosomal Mutations
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Mutations
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More Mutations
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Gene Regulation

• In simple cells (prokaryotic) lac genes which are
  controlled by stimuli, turn genes on and off.
• In complex cells (eukaryotic) this process is not
  as simple. Promoter sequences regulate gene
  operation.

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Review