Transcript The Central Dogma

Happy Thursday!
Submit Reading Guide for Essay, Replication
Errors and Mutation
• A few announcements
– Videos posted online
– Are you doing a type of cancer for your disease
project?
– Disease Project
Gene Expression:
How do genotypes become phenotypes?
Before these two cells form a zygote
(YOU!), how much genetic information
do each of them have?
Hint: A zygote has 46 chromosomes.
• Chromosome:
– Structure found in the nucleus of all* cells
– Made of DNA and protein, compacted
• DNA:
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–
–
–
Hereditary material “given” to us by our parents
Double helix shape
Stores genetic “gene” information
Self-replicates to produce 2 exact copies of itself
Gene:
– A segment of DNA that serves as a code for a specific product.
Ex: presence of dimples, curly hair, blood type A, etc.
Gene for hitchhikers thumb
The Big Picture
Gene for
hitchhikers
thumb
Genotype
Phenotype
inherit
Propose how this occurs. What other factors might be included
“within” the blue arrow? How do you go from alleles (A, a) to an
actual phenotype that is noticeable?
The Central Dogma
DNA
RNA
Protein
Transcription
Translation
Replication
DNA  RNA  Protein
DNA Structure
Nucleotides (monomers)
along one strand of
DNA are represented
by the bases
A, T, C, G
DNA Replication
• DNA, must be copied accurately to preserve an
organism’s genotype
• Occurs before a cell divides so the new cells will have
identical DNA
• Occurs before meiosis and before mitosis.
• Takes place in the nucleus.
• Enzymes used:
– Helicase: Unwinds double helix
– DNA Polymerase: Creates new strand
DNA Replication
• Complimentary base pairing rules:
A  T
C  G
• Make a complimentary strand of DNA
5’ CGTGGTTAAATCTGA 3’
After DNA replication, there’s enough
DNA to go around (in each cell)…you
can now begin to process/use it!
Gene Expression
Gene Expression
What does this look like in the cell?
Transcription
•
•
•
•
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The assembly of an RNA molecule from a DNA template
RNA = Ribonucleic Acid. Single strand.
Uses complimentary base pairing*
Takes place in nucleus
Enzyme that does this? RNA polymerase
Possible outcomes mRNA, tRNA, rRNA
Transcription
New Rules:
DNA
CG
GC
TA
AU
5’ GTACGTCTCCTCTAATT 3’
mRNA
Translation
• The assembly of polypeptides (which become proteins)
using the information from mRNA
• Enzyme* that does this? tRNA
• mRNA is “read” in triplets called codons
• Codons code for amino acids
• Chains of amino acids make up proteins
• Takes place in cytoplasm
DNA
RNA
Polypeptide
The
Genetic
Code 
AGGTACTCCTCTA ATT
UCCAUGAGGAGAUUAA
The Genetic Code
Translation
Alanine
Threonine
Glutamate
Leucine
Arginine
Serine
Stop!
Where to start / stop?
• Translation begins
– When enzyme spots AUG on mRNA
– AUG = “start codon”
– AUG translates to Methionine
• Translation stops
– 3 different stop codons: UAA, UAG, UGA
Some smaller details
DNA
5’ AGGCTATGGGATAC 3’  “Gene”/sense strand
3’ TCCGATACCCTATG 5’
template strand
mRNA
5’ AGGCUAUGGGAUAC 3’
Polypeptide
tRNA reads 5’  3’
Once your amino acid
sequence is complete, it
folds along itself and
becomes a protein!
Helps you express
your phenotype
Discuss with your neighbors:
1.
2.
3.
4.
5.
Where does DNA Replication take place?
Where does Transcription take place?
What does Transcription produce?
Where does Translation take place?
What does Translation produce?
6. The Genetic Code is used to figure out what amino
acids are assembled based on the
strand
created from the
strand
Your Task
• Work on Gene Expression Practice
Problems