1 DNA Replication What is it? When is it done? What is copied?
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Transcript of 1 DNA Replication What is it? When is it done? What is copied?
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DNA Replication
What is it?When is it done?What is copied?
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Two New, Two New, Identical Identical
DNA DNA Strands Strands Result Result from from
ReplicatiReplicati
onon
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PROTEIN PROTEIN SYNTHESISSYNTHESIS
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Protein Synthesis• After replication and cell division, each
new cell has its own DNA
• Now, how do those cells use that DNA to make proteins?
• How do you go from DNA (nucleic acid) to protein (amino acid)?
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Overview of Protein Synthesis
• Copy (mRNA) is made of gene
• mRNA sent out of nucleus
• Ribosomes use mRNA as instructions to make a protein
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Protein SynthesisProtein Synthesis
Two phases: Two phases: DNADNA
Transcription Transcription
mRNAmRNA
Translation Translation
proteinprotein
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TranscriptiTranscriptionon
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TranscriptionTranscription In nucleusIn nucleus
DNA the template for DNA the template for mRNAmRNA
RNA polymeraseRNA polymerase makes makes the mRNAthe mRNA
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Only one DNA strand is used
Just a portion of the DNA is copied (one gene)
copy is called mRNA
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RNA Differs from DNARNA Differs from DNA
DNA RNADeoxyribose
sugarRibose sugar
Double stranded
Single stranded
T (thymine) U (uracil)
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Question:Question:
What would be the What would be the complementary RNA complementary RNA strand for the following strand for the following DNA sequence?DNA sequence?
DNA 5’-DNA 5’-GCGTATGGCGTATG-3’-3’
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Answer:Answer:
•DNA 5’-GCGTATG-3’DNA 5’-GCGTATG-3’•RNA 3’-CGCAUAC-5RNA 3’-CGCAUAC-5’’
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TranslatioTranslationn
mRNA mRNA protein protein
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TranslationTranslation
ribosome
Ribosome reads the mRNA and makes protein
mRNA
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• mRNA leaves nucleus
• ribosome attaches to mRNA
• ribosome reads the bases in groups of 3 (codon)
AUG CUG
codon
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The ribosome uses the code to make the protein
How?
How do you go from nucleic acid to amino acid?
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tRNAtRNA
• Carries amino Carries amino acids to acids to ribosomeribosome
• Has Has anticodonsanticodons that are that are complementacomplementary to ry to mRNA mRNA codonscodons
U A C
Amino acid
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AUG CUG
UAC
A A
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Genetic CodeGenetic Code DNA contains a DNA contains a triplet codetriplet code
Every three bases on DNA Every three bases on DNA stands for stands for ONE amino acidONE amino acid
Codon: Codon: Each group of 3 bases Each group of 3 bases on on mRNAmRNA
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r
• http://www.wisc-online.com/objects/index_tj.asp?objid=AP1302
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Mutations
1. Gene Mutations
2. Chromosome Mutations
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What happens when there is a mistake during replication?
• What could go wrong when the DNA is being replicated?
• http://www.pbs.org/wgbh/nova/genome/program.html
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Gene Mutations
1. Point Mutations
A. Substitution
2. Frame shift MutationsA. Insertion
B. Deletion
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Point Mutations – substitution
One WRONG BASE is used
Original The fat cat ate the wee rat.Mutation The fat hat ate the wee rat
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Examples of Point Mutations
• Sickle Cell Anemia
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Examples of Point Mutations
• Tay Sachs Hemophilia B
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Frame Shift Mutations
A
• Insertion AAT AGG CAG GTT
• Deletion AAT AGG CAG GTT
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Frame Shift Mutations A
• Insertion AAT AGG CAG GTT
becomes AAT AAG GCA GGT …
• Deletion AAT AGG CAG GTT
becomes AAA GGC AGG …
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Frame Shift
• Original The fat cat ate the wee rat.
• Insertion The fat caa tet hew eer at.
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Example of Frame Shift Mutation:
Huntington’s Disease
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Chromosome Mutations
1. Inversions
2. Duplications
3. Deletions
4. Translocations
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Incorrect Chromosome Number –
from nondisjunction during meiosis
• Trisomy 21 causes Down’s Syndrome
• http://learn.genetics.utah.edu/units/disorders/whataregd/down/