DNA, RNA and Protein Synthesis

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DNA, RNA and Protein Synthesis

• Chapter 12
• Pgs. 287-312

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I. DNA discovery

• A. Franklin Wilkins- used X-ray diffraction,
  discovered DNA shape double helix like twisted
  ladder

Franklin
Wilkins
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I.
B. Watson Crick- Nobel prize, first
structural model of DNA
1953
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I.

• C. Chargaff- discovered amounts of
• Thymine Adenine,
• Cytosine Guanine,
• Nitrogen base-pairing rule

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I.

Double Helix
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II. DNADeoxyribonucleic acid
II.
DEOXYRIBOSE SUGAR (5C)
PHOSPHATE
NITROGEN BASE

• Monomer nucleotide
• 1. 5 C deoxyribose sugar
• 2. Phosphate group
• 3. Nitrogen base

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• B. Shape
• Ladders sides, also called backbone of
  alternating
• Deoxyribose sugars phosphates
• 2. Rungs nitrogen bases
• a. Bonded to each other by
• weak hydrogen bonds
• b. The nitrogen bases
• are bonded to the
• sugars of the ladder,
• NOT the phosphates

II.
D P D
D P D
A-T
G-C
P D P
P D P
C-G
T-A
D P D
D P D
G-C
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DNA Double Helix
C. Base pairing rule Adenine to Thymine
A-T Cytosine to Guanine G-C
II.
A
T
A
T
C
G
A
T
C
G
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1. Example Base Pairing
II.

• DNA Strand
• A T T C G G T A G
• T A A G C C A T C
• Complimentary DNA Strand

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II.

• D. DNA- forms chromosomes in nucleus and is found
  in mitochondria and chloroplasts

X
X
Chromosomes
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1. Stores genetic info Ex eye color 2. Tells
ribosomes which proteins to make
Eye color
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II.
3. DNA replication - DNA must make EXACT copy
of itself before cellular division enables new
cell to have SAME genetic info as dividing cell-
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III. DNA Replication-occurs in the nucleus BEFORE
cell division

• A. DNA unzips totally
• 1. ATP energy DNA helicase enzymes break the
  weak hydrogen bond between nitrogen
  basesseparates the 2 strands of DNA

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III.

• 2. Each parent strand of DNA is a template
  (pattern) for a new complementary strand
  additional proteins hold strands apart
• 3. DNA Polymerase enzymes add new nucleotides
  according to base pairing rule 2 new helices
  formed

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III.

• 4. Replication produces 2 DNA molecules each
  composed of a
• new original strand
• 5. Exact 2 copies of DNA that make up each
  chromosome are called chromatids
• 6. Two chromatids attached at centromere

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IV. RNARibonucleic Acid

• Monomer Nucleotides
• 5 C ribose sugar
• Phosphate group
• Nitrogen base
• Cytosine to Guanine
• Adenine to URACIL (replaces thymine)
• Shape single stranded

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V. Transcription- RNA synthesis (building RNA)

• A. DNA is copied into a complementary single
  strand of RNA occurs in nucleus b/c DNA never
  leaves nucleus
• B. mRNA- RNA that carries genetic message from
  DNA to the ribosomes in the cytoplasm (ribosomes
  make proteins)

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V. Transcription (cont.)

• C. Making RNA from DNA
• 1. RNA polymerase (enzyme)- unzips a short
  section of DNA
• 2.RNA polymerase adds, then links complementary
  RNA nucleotides as it reads the gene on the
  unzipped DNA

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V. Transcription (cont.)

• 3.Base pairing C to G/ A to U NO THYMINE in RNA
• 4. The 2 DNA strands close up by forming hydrogen
  bonds between complementary DNA bases, reforming
  the double helix.

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Example RNA Base Pairing

• DNA template strand
• A T G C G A T T A
• U A C G C U A A U
• RNA complementary strand

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V. Transcription (cont.)

• 5. In eukaryotic cells RNA goes through RNA
  splicing
• a. DNA contains regions that will not code for
  proteins
• b. Non-coding regions introns
• c. Coding regionsexons
• d. Spliceosomes- complex assemblies of proteins
  RNA, cut out introns and splice(put together)
  exons to form a smaller mRNA that will leave the
  nucleus through the nuclear pore.

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VI. Protein Synthesis

• A. Monomer- amino acids
• B. 20 different amino acids form all proteins
• C. DNA bases are arranged in triplets producing
  64 different 3 letter code words ex ATC, CAG

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VI. Protein Synthesis

• D. RNA bases written in 3 nucleotide sequences on
  the mRNA, called codons
• E. Each codon corresponds to an amino acid or a
  start or stop codon for translation into a
  protein
• AUG the start codon the amino acid methionine
• UAA, UAG, UGA stop codons, do not code for amino
  acid, protein stops here

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VI. Protein Synthesis

• F. mRNA leaves nucleus, attaches to ribosome in
  cytoplasm where protein synthesis will take place
• G. rRNA ribosomal RNA- most abundant RNA, rRNA
  and proteins form ribosomes

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IIV. Translation- RNA to Protein

• A. tRNA- single strand of RNA that temporarily
  carries a SPECIFIC amino acid
• B. tRNA is folded into a compact shape with an
  anticodon (a 3 nucleotide sequence on one end
  that it complementary to a codon on mRNA)

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IV. Translation (cont.)

• 1.Translation begins on the ribosome
• 2. A tRNA carrying amino acid, methionine, finds
  the mRNAs start codon AUG
• 3. tRNAs anticodon will pair with their
  complementary bases of the codon on the mRNA
  strand decoding the mRNA message into a specific
  protein

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IV. Translation (cont.)

• 4. Peptide bonds form between each amino acid as
  the protein chain grows C-N
• 5. The amino acid chain will grow until the tRNA
  reaches a stop codon on the mRNA UAA, UGA OR UAG
• 6. The ribosome complex falls apart and the newly
  made protein is released

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How do we know what Amino Acid to add?
USE THE mRNA CODE TO TRANSLATEINTO AMINO ACIDS
mRNA 1) CCC 2) CGG 3) ACU 4) UGA
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PRACTICE

• DNA T A C G A C G T A A A A A C T
• mRNA

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• DNA T A C - G A C - G T A - A A A - A C T
• mRNA A U G - C U G - C A U - U U U - U G A
• tRNA

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• DNA T A C - G A C - G T A - A A A - A C T
• mRNA A U G - C U G - C A U - U U U - U G A
• tRNA U A C - G A C - G U A - A A A - A C U
• AA Seq

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• DNA T A C - G A C - G T A - A A A - A C T
• mRNA A U G - C U G - C A U - U U U - U G A
• tRNA U A C - G A C - G U A - A A A - A C U
• AA Seq MET - LEU - HIS - PHE

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V. Mutations pg. 307-308

• A. Mutation- any change in the DNAs sequence of
  a gene or chromosome of a cell a mistake
• 1.Causes
• a. Radiation x-rays, cosmic rays, UV light
  nuclear radiation
• b. Chemicals dioxins, asbestos, benzene
  formaldehyde

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V. Mutation (cont.)

• B .Gene- section of DNA on a chromosome that
  directs the making of a protein or trait
• 1. A change in gene or chromosome a change in
  trait
• 2. Some mutations harmful

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V. Mutation (cont.)

• 3. Harmful mutations prevent the survival of an
  organism
• 4. Some mutations add genetic variety to a
  species

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V. Mutation (cont.)

• C. Gene Mutations
• 1. Point Mutation- a change in a single base pair
  of DNA which affects ONE codon can affect a
  single amino acid in a protein

Ex A T T G A A A C G U A A C C U U G C
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V. Mutation (cont.)

• a. Point mutation examples
• Sickle cell anemia GAA Glu, GUAVal causes a
  sickle shaped red blood cell these cells cannot
  deliver enough oxygen, causes tissue damage, clog
  capillaries

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V. Mutation (cont.)

• b. Cystic Fibrosis mutation produces thick mucus
  in lungs, liver and pancreas prevents oxygen
  intake in lungs prevents enzymes from reaching
  food in the digestive tract

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V. Mutation (cont.)

• 2. Frameshift Mutation- addition or deletion of a
  base

• Ex
• THE CAT ATE THE RAT
• THE ATA TET HER AT Deletion of base
• THE CAT ATE THE RAT
• THE CCA TAT ETH ERA T Addition of base

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V. Mutations (cont.)

• D. Chromosomal Mutations- occur when chromosomes
  break and rejoin incorrectly causing severe harm
• 1. Deletion part of a chromosome is left out
• Ex ABCDEFG- deletion- ABCEFG

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Chromosomal Mutations (cont)

• 2. Insertion part of chromosome breaks off and
  attaches to its sister chromatid, causing a
  duplication of genes on the same chromosome
  (duplication)
• Ex ABCDEFG-insertion-ABCBCDEF

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Chromosomal Mutations (cont)

• 3. Inversion part of a chromosome breaks off and
  reattaches backwards
• Ex ABCDEFG-inversion-ADCBEFG

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Chromosomal Mutations (cont)

• 4. Translocation part of one chromosome breaks
  off and is added to a different chromosome,
  results in too many genes on one chromosome and
  not enough on the other
• Ex ABCDEF- translocation- WXABCDEF
• WXYZ YZ

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The end of this unit!
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