October 8, 2010• Put strawberries on my desk for extra credit

Warm – Up:

Yesterday we watched a video over DNA…1. What is the universal genetic code stored in?

2. In DNA, how many bases are there?

3. What are the bases?

Griffith’s Experiments (1928)(Trying to discover vaccine for pneumonia)

Transformation PrincipleGene from one cell is taken in by another cell

Genes can be transferred between cells

Used different strains of bacteria

Avery and others (1944)

*Looked for molecule needed for transformation

-Used bacteria

**Transformation did not occur when enzymes added that break down DNA

***First to conclude: It is DNA that stores and transmits genetic information!

Hershey and Chase (1952)**Used bacteriophages

(Viruses that infect bacteria)

Used radioactive phosphorous (found in DNA) and sulfur (found in protein coat)

to determine whether protein or DNA makes up genes….

***Finally concluded that DNA makes up genes, NOT protein!

Bacteriophage with phosphorus-32 in DNA

Phage infectsbacterium

Radioactivity inside bacterium

Bacteriophage with sulfur-35 in protein coat

Phage infectsbacterium

No radioactivity inside bacterium

Figure 12–4 Hershey-Chase Experiment

ChargaffDiscovered percentage of

C (Cytosine) = G (Guanine)

and

T (Thymine) = A (Adenine)

Known as

Chargaff’s Rules – “Base Pairing Rules”

A always pairs with T

C always pairs with G

Complete the following using his base pairing rules:

A – T – C – G –

Francis CrickJames Watson

Watson and Crick (1953)

Built a 3D model of DNA

Franklin’s X-Rays gave great clues that DNA was a double helix structure

“Deoxyribonucleic Acid”

The molecule of heredity =

UNIVERSAL GENETIC CODE!

DNA Extraction Lab

Step One: • Place strawberry in the bag with 20mL of

salt water and seal. • Massage bag (squish strawberry) for 2

minutes. • Squeeze one drop of detergent into bag and

seal. • Massage bag CAREFULLY for an additional

2 minutes.

DNA Extraction Lab

Step Two: 1. Dampen cheesecloth

2. Cut a small hole in the corner of your ziploc bag

3. Press mixture onto cheesecloth into plastic cup.

Be sure to hold cheese cloth over cup!!!!!

4. If the mixture is too thick, add more salt water. Be sure to hold the bag closed while pouring more salt water!!!!!

DNA Extraction Lab

Step Three: 1. Tilt the cup and put 20 mL of ICE COLD

ethanol down the side of the cup

2. Use a stirring rod to gently spool (NOT stir) the DNA onto the rod by turning it continuously (DNA will be white and stringy)

DNA Extraction Lab

Final Step:

Clean up! 1. Do NOT throw solids down the sink!

2. DO NOT poor left over salt water down the sink – leave it on the table!

3. Clean out your plastic cup.

4. Throw everything away in the trash except for the plastic cup, scissors, and wooden sticks.

Structure of DNA nucleotides:

1. Deoxyribose sugar

2. Phosphate group

3. Nitrogenous (nitrogen-containing) base

4 Possible Bases

Adenine (A)Guanine (G)Cytosine (C)Thymine (T)

Purines Pyrimidines

Adenine Guanine Cytosine Thymine

Phosphate group Deoxyribose

DNA Nucleotides

How do A & T fit and G & C fit together?

Due to hydrogen bonding

Sequence of bases can vary in countless ways…

Each gene has a unique order or base sequence.

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

 DNA Shape

Double helix – twisted ladderBackbone (sides) of sugar and phosphate

Rungs (steps) of bases A-T and G-C

If one side of the DNA molecule has this arrangement of bases, what would the other side look like? Draw it including the base pairs and sides of the ladder.

ACGAATCGGTTAGCCAT

October 23, 2009

Warm – Up: • What are the 3 parts of a DNA molecule – the monomer?• What are the 4 bases in a molecule of DNA?• What type of bond holds two bases together?• What bonds with A?• What bonds with G?• What is the shape of DNA?

– What is the backbone made up of?– What are the rungs of the ladder made up of?

Replication of DNA

FYI – Each of your cells has 46 chromosomes which is over 6 billion base pairs. If one letter symbols were printed in normal type, it would fill about 900 books as big as your biology textbook. This amount of DNA is copied in just a few hours with only a few errors per billion nucleotides.

DNA is copied…

                       

In eukaryotes, enzymes (protein!) split and unwind DNA by breaking the hydrogen bonds

between bases.

.

An enzyme add new nucleotides along the

template strand of DNA one at a time.

The same enzyme proofreads each

nucleotide and corrects errors so very few occur.

In humans, DNA is copied at about 50 base pairs per second. A cell’s

DNAis copied with less than one mistake

in abillion nucleotides. This is equal to a

person copying 100 large (1000 page)

dictionaries word for word with only one

error!

DNA Replication

Growth

Growth

Replication fork

DNA polymerase

New strand

Original strand DNA

polymerase

Nitrogenous bases

Replication fork

Original strand

New strand

Protein Synthesis

After replication…

TRANSCRIPTION and

TRANSLATION

October 26, 2009

• Write down your objectives and activities!

• Take out your homework and leave it on your desk!!

• Take out your notes from DNA Replication.

WARM – UP:

1. What are the three steps of DNA replication?

2. What is the end result of DNA replication?

3. Where does DNA replication occur?

Transcriptionand

Translation

DNA RNA (Transcription)

RNA Protein (Translation)

RNA – The “Other” Nucleic Acid

Differs from DNA :

1. RNA is a single strand of nucleotides DNA is a double strand of nucleotides (helix)

2. Ribose is sugarDeoxyribose is sugar in DNA

3. No Thymine, Uracil (U) replaces Thymine

•Messenger RNA (mRNA)

•Ribosomal RNA (rRNA)

•Transfer RNA (tRNA)

Three Forms:

Key Players:

Ribosome - rRNAtRNA – transfer RNA

mRNA – messenger RNALeaves nucleus with instructions!

Transcription

**Occurs in the nucleus

1. Different enzyme binds to the start signal on DNA

2. Unwinds and separates DNA

3. One side of DNA is used as the templateto make the copy of RNA

4. RNA Nucleotides bind with complementary bases

(U pairs with A)

5. Complete when enzyme reaches the stop code

TTATGCATCG

What will be the complimentary RNA sequence?

New RNA dangles off the enzyme

DNA closes back to a double helix shape

Working copy of RNA is edited

Introns – Noncoding (intervening) sequences– edited out

Exons – Code for amino acids – (exit nucleus) spliced together

Example: ACAAUGGACAGU

is the RNA code

If the code for the protein is ACUGGU, what are the introns/exons?

mRNA – Blueprint for protein synthesis travels from nucleus to ribosome

Three Types of RNA Made in Transcription

tRNA – Translates mRNA code to amino acids

(monomers of protein!)

rRNA – Makes up ribosomes

The Genetic Code

Instructions for building a protein come from:

Codon – 3 base code on mRNA – codes for amino acids or is a stop

signal

Genetic code is nearly universal for all organisms!!

20 Different kinds of amino acids

Sequence of three bases gives enough different combinations to code for all of them = CODONS!

64 possible codons – 61 code for amino acids

3 are stop signals

Each codon codes for one AA, but there is more than one codon for most AA.

Codons

The Genetic Code

Remember the Key Players…

ribosometRNA

mRNA

Translation

*Occurs on ribosomes

*Strings Amino Acids together to form protein!

tRNA

RNA folded with three loops

One loop has three nucleotide sequence (Anticodon)

which is complementary to mRNA codon

For example, if codon is CAAanticodon would be GUU…

“End” of tRNA carries AA that corresponds

with the codon (codon comes from

wheel/chart)

No anticodon for codonsUAG, UAA, OR UGA

(Stop Codons)

1. mRNA leaves nucleus & binds to ribosome

2. tRNA with anticodon UAC and AA Methionine binds to start codon

Translation

3. Next tRNA comes to ribosome

4. Enzyme joins two AA

Ribosome

mRNA tRNA

5. 1ST tRNA leaves

6. 2ND tRNA slides over bringing the mRNA and AA chain along tRNA

mRNA codon

tRNAanticodon

Amino AcidChain

7. Next codon in ribosome is ready for new tRNA anticodon (Process continues…)

Finally, Step 9…. Ribosome complex falls apart releasing new protein!!!

8. Continues until stop codon

from to to make up

Concept MapSection 12-3

also called which functions to also called also called which functions towhich functions to

can be

RNA

Messenger RNA Ribosomal RNA Transfer RNA

mRNA Carry instructions rRNACombine

with proteins tRNABring

amino acids toribosome

DNA Ribosome Ribosomes