RNA and Protein Synthesis

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RNA and Protein Synthesis

• Chapter 12, section 3

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The Structure of RNA

• RNA, like DNA, is made up of nucleotides
• However, there are 3 differences between DNA and
  RNA
• RNA has ribose instead of deoxyribose
• RNA has uracil instead of thymine
• RNA is single-stranded instead of double-stranded

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3 Types of RNA

• Messenger RNA (mRNA) carries the message from
  the DNA to the ribosomes
• Ribosomal RNA (rRNA) make up part of the
  structure of a ribosome
• Transfer RNA (tRNA) transfers amino acids to
  the ribosomes

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Transcription

• Making RNA from DNA (in the nucleus)
• RNA polymerase binds to a special region of DNA
  called a promoter
• The RNA polymerase then separates the DNA strands
  and uses one of the strands as a template
• A will now pair with U, T still pairs with A
• C and G still pair with each other

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Transcription
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Practice Transcription

• DNA AGCTCCGATGCATACTTGCCA
• RNA UCGAGGCUACGUAUGAACGGU
• DNA GCCAGTGCTTACGAACTGAGT
• RNA - CGGUCACGAAUGCUUGACUCA

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RNA Editing

• RNA requires a little editing before it is ready
  to go to the ribosome to make proteins
• Introns sections of RNA that do not code for a
  protein (in the way)
• Cut out
• Exons sections of RNA that do code for a
  protein (expressed)
• spliced back together

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RNA Editing
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The Genetic Code

• Proteins are made of amino acids
• There are 20 different amino acids
• A codon is a 3 base sequence that codes for a
  specific amino acid
• There are 64 possible codons

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The Genetic Code
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The Genetic Code

• RNA sequence
• UCGCACGGU
• Separate into codons
• UCG-CAC-GGU
• Identify the amino acids
• Serine-Histidine-Glycine

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Translation

• Making the proteins from the mRNA (translating
  the code)
• Occurs on the ribosomes

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Translation

• mRNA must be transcribed from the DNA in the
  nucleus and released into the cytoplasm
• The mRNA attaches to the ribosome
• The tRNA brings the proper amino acid to the
  ribosome
• Anticodon sequence of bases on the tRNA that
  pair with the mRNA

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Translation

1. The amino acids form a peptide bond to hold them
   together
2. The next amino acid is brought in and is attached
3. This continues until the ribosome reaches a stop
   codon
4. The completed protein is then released

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Translation
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Mutations

• Changes in the DNA sequence that affect genetic
  information
• Gene mutations result from changes in a single
  gene
• Chromosomal mutations involve changes in whole
  chromosomes

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Gene Mutations

• Point mutations a mutation that occurs at a
  single point (only 1 nucleotide is changed)
• Substitution a single nucleotide is substituted
  for another one (A instead of G)
• Missense changes the amino acid to a different
  amino acid
• Nonsense changes to one of the STOP codons
• Insertion a nucleotide is added
• Deletion a nucleotide is removed

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Gene Mutations

• Insertions and deletions cause frameshift
  mutations because they shift the reading frame
  of the genetic message.

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Chromosomal Mutations

• Deletion a section of a chromosome is deleted
• Duplication a section of a chromosome is copied
  and inserted
• Inversion a section of a chromosome is moved
  from one spot to another
• Translocation a piece of a chromosome is moved
  from one chromosome to another

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Chromosomal Mutations