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

Gene Expression

What does this look like in the cell?

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