happy thursday! submit reading guide for essay, replication errors and mutation a few announcements...
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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?
From mom
From Dad
Before these two cells form a zygote (YOU!), how much genetic information
do each of them have? Hint: A zygote has 46 chromosomes.
One gamete
(sex cell)
Another gamete
• Chromosome:
– Structure found in the nucleus of all* cells – Made of DNA and protein, compacted
• DNA:
– 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 hitch-hikers thumb
The Big PictureGene for hitch-hikers 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
DNA RNA Protein
Transcription Translation
Replication
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
Transcription• 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 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 AGGTACTCCTCTA ATTRNA
UCCAUGAGGAGAUUAA
Polypeptide
The
Genetic
Code
The Genetic Code
TranslationAlanine
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’ tRNA reads 5’ 3’
Polypeptide
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. Where does DNA Replication take place?
2. Where does Transcription take place?
3. What does Transcription produce?
4. Where does Translation take place?
5. 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
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