Originally, people thought protein was genetic material because it was complex.

However, the work of 4 scientists showed it was really DNA…

1928- Frederick Griffith* was trying to find a vaccine for pneumonia using mice

* ended up finding out in the process that the bacteria could transform from a harmless type into a virulent type...didn't know how this happened!

1944 - Oswald Avery* was trying to determine what was responsible for transformation… DNA, RNA, or protein

* Used enzymes to determine this...

1952 - Hershey and Chase* supported Avery's findings by showing how DNA

was passed on to other cells

* Used a bacteriophage - virus that infects bacteria

*provided definitive proof that DNA was genetic material...could trace it being passed from

one generation to the next!

DNA!!

Martha and Alfred

Rosalind Franklin - 1953

* Used x-ray diffraction to make images of DNA

* The images suggested that DNA had a spiral shape

Watson and Crick - 1953* developed a 3-D model of DNA and it looked like a twisted or spiral staircase == double helix

Erwin Chargaff - 1949

* Came up with the base-pairing rule...

* Noticed that the amount of Adenine = amount of Thymineand the amount of Guanine = amount of Cytosine

* Total amounts of these bases vary by organism

* He basically said that how the base pairs are arranged, determine what genes they are

http://highered.mcgraw-hill.com/olc/dl/120076/bio21.swf

So for example... If a strand ( one side) has the sequence of

GATCTGACCTGAT

The complimentary strand would be...??

CTAGACTGGACTA

DNA is made up of nucleotides linked together in a chain Each nucleotide is made of 3 parts:

1.) Phosphate group2.) 5 C sugar molecule - called deoxyribose3.) Nitrogen base

The bases are:

Adenine Thymine

Guanine Cytosine

only A can bind with T and only G can bind with C

~ this makes the 2 strands complementary

Replication of DNA

Done in steps:

1.) DNA must be unwound~done by an enzyme...Helicase

2.) Strand are held apart by other enzymes

3.) Yet another enzyme - DNA polymerase - adds nucleotides according to the base-pairing rules

This makes exact copies of the strands!!

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120076/micro04.swf::DNA%20Replication%20Fork

Let's see it in action!

6-2

After discovering genes, how does this info translate into traits?

Answer: the genes tell us what proteins to make and these lead to the traits!

But how does DNA determine proteins?

Well… proteins are NOT made directly from genes!~ genes act like instructions for building

proteins

*working instructions are made of RNA - ribonucleic acid

Blueprint

How is RNA different from DNA?1.) Single strand of nucleotides2.) Has the 5 C sugar ribose instead of

deoxyribose3.) Has the base Uracil (U) instead of Thymine

(T)

*U is complementary to A!!!

**So you will never see T on a strand of RNA...and you will never see U on a strand of DNA!!

RNA present in many forms...but we will learn 3:1.) mRNA - messenger~ RNA copy of a gene used as a blueprint for a protein~ carries and delivers the message to the site of translation~ serves as a template for AA assembly

2.) rRNA - ribosomal~ used during translation

3.) tRNA - transfer~ carries specific amino acids - determined by the bases on the tRNA

All of these are used for gene expression- *2 stages:1.) Transcription - info from DNA transferred to

mRNA~ think of writing…you transcribe something!

2.) Translation - info from mRNA used to make protein~ just like in Spanish… Hola = hello! You're translating!

Hola hello

Transcription: * This re-writes the info from DNA and makes mRNA

* With help from an enzyme, the DNA gets spilt and one side of the DNA is used to make a strand of mRNA - thus creating a message!

http://highered.mcgraw-hill.com/sites/0072507470/student_view0/chapter3/animation__mrna_synthesis__transcription___quiz_1_.html

Let's see how it works...

Let's write it out...

1.) An enzyme sticks to a promoter (start place) and breaks the strand open.

2.) Then, it adds the matching bases to one side of the DNA strand

3.) The mRNA with its "message" hangs off the DNA like a tail

4.) The mRNA leaves the DNA strand

**The mRNA with the message then needs to

leave the nucleus to take it to make the protein!**

Translation

* Recall that this is info from mRNA used to make proteins!

This stage takes place in the cytoplasm!

The mRNA takes its "message" to a ribosome

The message gets "read" by the ribosome

Depending on the message, a tRNA with a matching Amino Acid attached will come in and stick to the mRNA. It does this by matching the base pairs...

The tRNA releases the AA which become linked together in a chain.

When the mRNA goes through and reaches the end, the protein is done and is released back in to the cell

Mutations

A mutation is any change in the structure, order, number, or type of base on a DNA strand

Several types of mutations can happen:

1.) Deletion: a base is left out

2.) Insertion: extra base added

3.) Substitution: wrong base is used

So does a mutation matter??

It depends...! Most mistakes are corrected before they can become a problem...however...

Possible outcomes:

1.) No change - the AA is the same

2.) Improved trait - The protein produced is different but better!

3.) Harmful or fatal trait - protein is defective - can cause didease or death!

http://sciencestage.com/v/1299/dna-mutation.html

Let's see how this works:

What causes mutations?

Sunlight! Every time you step outside, you damage your DNA!

Cigarette smoke! Every time you smoke or are around second hand smoke, you can mutate your DNA!

Some are random and happen naturally during the copying process. Others are from outside sources such as...

Examples of effects from mutations:

Sickle Cell Anemia

~Caused by a substitution

~ Makes the protein hemoglobin defective - can't carry O2 well

~ Can clog blood vessels- lead to pain and dangerous clots

Hemophilia:~ Blood clotting disorder!

~ Caused by a mutation resulting in a recessive allele

~ Is inheritable - seen in royal families for many generations!~ Is an x-linked recessive! males more than females are affected

Queen Victoria and family

What can we use Genetics for today?

Genetic Engineering:

Scientists can take genes from one organism and insert them into other organisms where they become expressed!

Pros:

~Pest-resistant Crops and Longer Shelf life~Genetic Modification to Produce New Foods~Better Taste, Nutrition and Growth Rate~Modification of Genetic Traits in Humans~Boost Positive Traits, Suppress Negative Ones~Modification of Human DNA

~Production of Human Insulin~ Use in Gene Therapy

Cons:

~May Hamper Nutritional Value~May Lead to Genetic Defects~Detrimental to Genetic Diversity~May Introduce Harmful Pathogens

**Some people may also have a moral and ethical problem with "messing" with the natural order of things.**