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Genes and Proteins
Genetic Role and Structure of DNA
• Hershey and Chase experiments
– Showed that viruses inject their DNA into bacteria and...
Genetic Role and Structure of DNA
• Hershey and Chase experiments and Rosalind
Franklin
– Showed that viruses inject their...
The Structure of DNA (review)
DNA has (a) a double helix structure and (b) phosphodiester bonds. The (c) major and minor
g...
Base Pairing
Double Helix
Structure
DNA vs. RNA
• Same basic structure
• Instead of thymine use uracil to pair with adenine
• Single helix
• Helps code for an...
DNA vs. RNA
DNA encodes the
genetic instructions
used in
development and
function; transfers
to daughter cells
RNA plays a...
The Genetic Code
• Genome – All the genetic material in cells
– All different sizes depending on complexity of
organisms
•...
Protein Synthesis
• Transcription – Copying a gene’s DNA to a
complementary RNA molecule, occurs in
nucleus
• Translation ...
Transcription and Translation
Transcription occurs within the nucleus; translation occurs
outside (still within the cell)
Transcription
• Transcription – Copying a gene’s DNA to a
complementary RNA molecule, occurs in nucleus
– Just copying the...
Transcription
Preparation for Translation
• Bacteria and archaea begin translation as RNA
molecule is being transcribed
• Eukaryotic cel...
The mRNA then leaves the nucleus of the cell; ribosomes translate from mRNA.
Translation
• Translate DNA/RNA language into a amino
acid language to make protein
• Uses
– mRNA – carries codon informat...
Large subunit
• 5,080 RNA bases
• ~49 proteins
Small subunit
• 1,900 RNA bases
• ~33 proteins
Small subunit
Large subunit
...
tRNA
Tertiary structure of tRNA.
CCA tail in yellow, Acceptor
stem in purple, Variable loop
in orange, D arm in red,
Antic...
tRNA and the ribosome combined
Triplet Codon
Translation
• Occurs in 3 Steps
– Initiation – at 5’ end “start” codon (AUG) codes for
methionine, calls large subunit, st...
Steps in Translation
Steps in
Translation
Polypeptide to Protein
• Polypeptide chain is NOT a protein
• Chain folds in cytoplasm to get 3-D structure
• Errors can o...
How Do Prokaryotic Cells Express
Proteins?
• Operons
How Do Prokaryotic Cells Express
Proteins?
• Operons
– Used by bacteria
– Group of genes plus promoter and
operator/repres...
How Do Prokaryotic
Cells Express Proteins?
• Lac Operons: lactose turns
off the repressor
How Do Prokaryotic Cells Express
Proteins?
• TRP Operon : presence of TRP = active repressor
How Do Eukaryotic Cells Express
Proteins?
• All cells in an organism contain identical DNA
sequences.
– i.e. cloning exper...
How Do Eukaryotic Cells Express
Proteins?
• All cells in an organism contain identical DNA
sequences.
– i.e. cloning exper...
How Do Eukaryotic Cells Express
Proteins?
• Transcription Factors
– Eukaryotic Cells
– Bind to DNA at different sequences ...
How Do Eukaryotic Cells Express
Proteins?
How Do Eukaryotic Cells Express Proteins?
• DNA Availability
– If DNA not “unwound” from double helix, cannot do
transcrip...
How Do Cells Express Proteins?
• RNA Processing
– Removal of introns to change what proteins are
coded for
How Do Eukaryotic Cells Express
Proteins?
• Methylation of certain portions of DNA can
deactivate those genes
• X-inactiva...
Mutations
• Mutation – Change in cell’s DNA sequence
• Not always harmful, can lead to genetic variability
• Point Mutatio...
Mutations: Substitution
Missense
Mutations
• Base Insertions and Deletions
– 1 or more nucleotides are added or subtracted from
gene
• Frameshift Mutation ...
Mutations: Deletions
Mutations: Deletions
How are these Mutations Produced?
• Unmatched base pairs can
possibly lead to changes in
the DNA structure
How are these Mutations Produced?
• Unmatched base pairs can possibly lead to
changes in the DNA structure
Wild-Type Seque...
Mutations
• Causes
– Spontaneous – DNA replication error
– Mutagens – external agent that induces mutations
• UV Radiation...
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Genes and proteins updated

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Genes and proteins updated

  1. 1. Genes and Proteins
  2. 2. Genetic Role and Structure of DNA • Hershey and Chase experiments – Showed that viruses inject their DNA into bacteria and direct bacteria to replicate it for them • DNA not protein is genetic material • DNA – Double helix – Made of EQUAL amounts of nucleotides: Adenine, Guanine, Cytosine, Thymine – Each part of helix is complementary to other, run in opposite directions – 3 prime and 5 prime ends
  3. 3. Genetic Role and Structure of DNA • Hershey and Chase experiments and Rosalind Franklin – Showed that viruses inject their DNA into bacteria and direct bacteria to replicate it for them • DNA not protein is genetic material Alfred Hershey Alfred Hershey
  4. 4. The Structure of DNA (review) DNA has (a) a double helix structure and (b) phosphodiester bonds. The (c) major and minor grooves are binding sites for DNA binding proteins during processes such as transcription (the copying of RNA from DNA) and replication.
  5. 5. Base Pairing
  6. 6. Double Helix Structure
  7. 7. DNA vs. RNA • Same basic structure • Instead of thymine use uracil to pair with adenine • Single helix • Helps code for and make proteins • Types of RNA – Messenger RNA (mRNA) – carries info. For a specific protein. Segment is codon – Ribosomal RNA (rRNA) – combines with proteins to form ribosome – Transfer RNA (tRNA) – connectors to bind an mRNA codon to a specific RNA
  8. 8. DNA vs. RNA DNA encodes the genetic instructions used in development and function; transfers to daughter cells RNA plays an active role within cells by catalyzing biological reactions, controlling gene expression, or sensing and communicating responses to cellular signals
  9. 9. The Genetic Code • Genome – All the genetic material in cells – All different sizes depending on complexity of organisms • Chromosome – Package of DNA and associated proteins – You have 23 pairs or 46 total chromosomes • Gene – sequence of DNA on a chromosome that codes for a specific protein or RNA molecule
  10. 10. Protein Synthesis • Transcription – Copying a gene’s DNA to a complementary RNA molecule, occurs in nucleus • Translation – Copying translating an mRNA strand into the language of amino acids
  11. 11. Transcription and Translation Transcription occurs within the nucleus; translation occurs outside (still within the cell)
  12. 12. Transcription • Transcription – Copying a gene’s DNA to a complementary RNA molecule, occurs in nucleus – Just copying the “words” • Occurs in 3 Steps – Initiation – Enzymes unzip DNA double helix, RNA polymerase binds to promoter • Promoter – DNA sequence at the beginning of a gene – Elongation – RNA polymerase, adds nucleotides from 3’ to 5’ end making RNA molecule – Termination – RNA polymerase gets to termination sequence at end of gene, separates and releases new RNA molecule
  13. 13. Transcription
  14. 14. Preparation for Translation • Bacteria and archaea begin translation as RNA molecule is being transcribed • Eukaryotic cells – mRNA can’t cross nuclear membrane – Add nucleotide cap to end of 5’ end of mRNA – Add 100-200 adenines – “poly a-tail” – Helps ribosomes attach to 5’ end of mRNA – Helps prevent degradation of mRNA – Introns removed from RNA, exons spliced together
  15. 15. The mRNA then leaves the nucleus of the cell; ribosomes translate from mRNA.
  16. 16. Translation • Translate DNA/RNA language into a amino acid language to make protein • Uses – mRNA – carries codon information – tRNA – binds to mRNA and amino acid – Ribosome – anchors mRNA • Functional Unit = Codon – 3 base pair “word” that coincides with an amino acid – Genetic Code
  17. 17. Large subunit • 5,080 RNA bases • ~49 proteins Small subunit • 1,900 RNA bases • ~33 proteins Small subunit Large subunit Ribosome
  18. 18. tRNA Tertiary structure of tRNA. CCA tail in yellow, Acceptor stem in purple, Variable loop in orange, D arm in red, Anticodon arm in blue with Anticodon in black, T arm in green.
  19. 19. tRNA and the ribosome combined
  20. 20. Triplet Codon
  21. 21. Translation • Occurs in 3 Steps – Initiation – at 5’ end “start” codon (AUG) codes for methionine, calls large subunit, start polypeptide – Elongation – tRNA brings 2nd amino acid, covalently bonds with 1st amino acid, release 1st tRNA, get another tRNA and so on to make poly peptide chain – Termination – “Stop” codon (UGA, UAG, or UAA). NO amino acid corresponds to “stop”, release factors, release last tRNA, ribosomal units separate, polypeptide chain released
  22. 22. Steps in Translation
  23. 23. Steps in Translation
  24. 24. Polypeptide to Protein • Polypeptide chain is NOT a protein • Chain folds in cytoplasm to get 3-D structure • Errors can occur – Wrong amino acid sequence “messes” up folding • Cystic fibrosis – Error in folding with correct sequence • Alzheimer Disease – incorrect folding of amyloid, forms mass in brain – Error in joining polypeptide chains • Misfire in types or how joined. Hemoglobin
  25. 25. How Do Prokaryotic Cells Express Proteins? • Operons
  26. 26. How Do Prokaryotic Cells Express Proteins? • Operons – Used by bacteria – Group of genes plus promoter and operator/repressor • Operator – DNA sequence between promoter and protein encoding region • Repressor – Protein that binds to operator to inhibit transcription
  27. 27. How Do Prokaryotic Cells Express Proteins? • Lac Operons: lactose turns off the repressor
  28. 28. How Do Prokaryotic Cells Express Proteins? • TRP Operon : presence of TRP = active repressor
  29. 29. How Do Eukaryotic Cells Express Proteins? • All cells in an organism contain identical DNA sequences. – i.e. cloning experiments on plants
  30. 30. How Do Eukaryotic Cells Express Proteins? • All cells in an organism contain identical DNA sequences. – i.e. cloning experiments on animals
  31. 31. How Do Eukaryotic Cells Express Proteins? • Transcription Factors – Eukaryotic Cells – Bind to DNA at different sequences to control transcription – Can bind to promoter or enhancer – Respond to external stimuli to signal gene to “turn on” • Signaling molecule binds to outside of cell, triggering reactions inside – Defects can cause disease or be used as drugs • Cancer • RU486
  32. 32. How Do Eukaryotic Cells Express Proteins?
  33. 33. How Do Eukaryotic Cells Express Proteins? • DNA Availability – If DNA not “unwound” from double helix, cannot do transcription • Molecules bind to DNA and either not allow to unwind or wind it even tighter
  34. 34. How Do Cells Express Proteins? • RNA Processing – Removal of introns to change what proteins are coded for
  35. 35. How Do Eukaryotic Cells Express Proteins? • Methylation of certain portions of DNA can deactivate those genes • X-inactivation The coloration of tortoiseshell and calico cats is a visible manifestation of X-inactivation. The black and orange alleles of a fur coloration gene reside on the X chromosome. For any given patch of fur, the inactivation of an X chromosome that carries one gene results in the fur color of the other, active gene.
  36. 36. Mutations • Mutation – Change in cell’s DNA sequence • Not always harmful, can lead to genetic variability • Point Mutation – changes 1 or a few base pairs in a gene – Substitution – replacement of 1 DNA base pair with another • Silent – mutation codes for same protein • Missense – mutation codes for different amino acid, changing proteins shape (ex. Sickle cell anemia) • Nonsense – mutation codes for “stop” codon instead of amino acid – makes shorter peptide chain
  37. 37. Mutations: Substitution
  38. 38. Missense
  39. 39. Mutations • Base Insertions and Deletions – 1 or more nucleotides are added or subtracted from gene • Frameshift Mutation – adds or deleted nucleotides in any number other than multiple of 3 – Disrupts codon reading, alters amino acid sequence • Expanding Repeats – Number of a 2 or 4 nucleotide sequence increases over several generations • Symptoms get more and more severe • Huntington’s Disease – makes extra glutamines, makes fibrous clumps in brain
  40. 40. Mutations: Deletions
  41. 41. Mutations: Deletions
  42. 42. How are these Mutations Produced? • Unmatched base pairs can possibly lead to changes in the DNA structure
  43. 43. How are these Mutations Produced? • Unmatched base pairs can possibly lead to changes in the DNA structure Wild-Type Sequence DNA CTG ACT CCT GAG GAG AAG TCT Protein Leu Thr Pro Glu Glu Lys Ser Amino Acid Position 3 4 5 6 7 8 9 Sickle Cell Sequence DNA CTG ACT CCT GTG GAG AAG TCT
  44. 44. Mutations • Causes – Spontaneous – DNA replication error – Mutagens – external agent that induces mutations • UV Radiation, x-rays, chemical weapons, nuclear energy, tobacco – During Meiosis – Transposons – jumping pieces of DNA • Types – Germline – occurs in cells that give rise to sperms and eggs • Things that run in families – Somatic – occurs in non-sex cells • DOES NOT get passed on

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