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 Thymine and 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
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Originally, people thought protein was genetic material because it was complex. However, the work of 4 scientists showed it was really DNA… 1928- Frederick.
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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
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!
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.**