Genetic Tranmission

1
Genetic Tranmission
2
Warm up

• Group 1 Griffith experiment (279)
• Group 2 Avery experiment (279)
• Group 3 Hershey-Chase (279-280)
• Group 4 Watson-Crick and Franklin (281-283)
• Group 5 Meselson-Stahl experiment (284-285)
• Write out a brief summary and state the
  significance of the experiment(s) on the
  transparency

3
DNA structure

• Antiparallel

4
DNA replication
5
Origin of replication

• Bacteria chromosomes
• 1 replication origin
• Recognized by a specific sequence
• Eukaryotic chromosomes
• Hundreds or thousands of replication origin
• Multiple Replication bubbles occur
  simultaneously

6
(No Transcript)
7
Elongation
8
Elongation

• ss binding proteins hold strands apart
• Primase joins RNA nucleotides to template
  (primer)
• DNA polymerase III joins DNA nucleotides to
  template
• DNA polymerase I replaces primer
  with DNA nucleotides

9
Elongation (more nuances)

• Nucleoside triphosphate links to backbone, losing
  2 phosphates (ENERGY!)
• Lagging strand
• Proceeds away from the replication fork
• Requires new primer for every okazaki fragment
  (100 200 nucleotides)
• Fragments joined by ligase

10
DNA replication - summary
11
DNA replication summary
12
What is a gene? Beadle and Tatum
13
What is a gene?

• A DNA segment has information for making the
  protein hemoglobin, which carries oxygen in your
  red blood cells
• One allele will give information for producing
  normal hemoglobin
• -Another allele (ONLY 1 base different) produces
  hemoglobin with 1 different amino acid
• This difference makes the hemoglobin less soluble
• When Oxygen levels are low, the hemoglobin
  molecules start sticking together, resulting in
  the red blood cells sickle-shape
• Having both defective alleles will lead to
  multiple effects shown to the right

14
What is a gene?

• Having only 1 defective allele (heterozygous)
  will not be fatal and actually beneficial!
• Malaria is a disease spread by mosquitois that
  infects red blood cells
• Being heterozygous results in your body
  destroying the red blood cells as well as the
  Malaria, leaving enough of the normal blood
  cells.

15
What is a gene?

• Mendelian definition
• Morgan definition
• 1 gene-1polypeptide definition
• What about noncoding region, non translated RNA?
• Region of DNA whose final product is either a
  polypeptide or an RNA molecule What do you think?

16
Genetic code
17
Genetic code
18
Transcription
19
1. Transcription initiation

• Prokaryotes - RNA polymerase attaches to the
  promoter (startpoint and upstream nucleotides)
• Eukaryotes Transcription factors bind to TATA
  box region of promoter ? RNA polymerase II binds
  to promoter (transcription initiation complex)

20
Transcription elongation and termination

• 2. RNA polymerase untwists DNA and joins RNA
  nucleotides (DNA rejoins as RNA strand peels
  away)
• 3. Prokaryotes termination at a DNA certain DNA
  sequence
• Eukaryotes RNA polymerase goes beyond
  termination sequence (AAUAAA polyadenylation)

21
Eukaryotic RNA modification

• 5 end modified GTP (protect from degradation
  and is signal for ribosomes)
• 3 end poly(A) tail (same functions and
  facilitates export from the nucleus)
• RNA splicing

22

• Post transcriptional nuances
• Some organisms intron RNA catalyzes splicing
  (ribozymes)
• Introns may perform regulatory roles
• Domains

23
(No Transcript)
24
tRNA structure and function

• There are 61 codon
  combinations,
  but only 45
  different
  tRNAs. Why?
• Wobble
  position (A or G )

25
Connecting a.a. to
the correct tRNA
26
Ribosome structure and function
27
Translation - initiation

• mRNA, tRNA, ribosomal subunits brought together
  with help of initiation factors
• 1. Small ribosomal subunit binds to mRNA and
  initiator tRNA
• 2. Large ribosomal subunit attaches

28
Translation - elongation
29
Translation - termination
30
Translation nuances

• Polyribosomes
• Posttranslational modifications chemical
  modifications, removal of amino acids,
  polypeptide cleaved, joining of 2 polypeptides
  (hemoglobin)

31
DNA repair

• Replication problems?
• Initial paring errors 1/10,000 bases
• However, completed DNA has only 1 error in every
  1,000,000,000 bases
• DNA polymerase cant add to the 5 end of
  daughter DNA strands (why dont prokayrotes have
  this problem?)

32
DNA repair solutions!

• Mismatch repair DNA polymerase proofreads
  nucleotides as it is added and corrects it
  immediately
• Additional proteins perform mismatch repair
• Excision repair (already damaged DNA) nuclease
  removes DNA segment and DNA polymerase and ligase
  fill in with correct nucleotides

33
DNA repair solutions!

• Telomeres (non coding repeated sequence TTAGGG)
• Telomerase lengthens telomeres by incorporating
  its own RNA as template for new segment
• Not found in most cells only germ line cells
  and cancerous cells

34
Mutations

• Make a mini concept map using MOST or ALL of the
  following terms (feel free to add more)
  mutations, point mutations, substitutions,
  insertions, deletions, frameshift mutation,
  mutagens, missense mutations, nonsense mutations,
  wild type, codon, polypeptide, DNA replication,
  recombination, DNA repair, nondisjunction,
  aneuploidy, polyploidy, duplication, inversion,
  translocation, deletion