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February 25, 2010

 

Objective: To learn about the basic building block of life DNA

 

Vocab (put in vocab section of your notebook): Deoxyribonucleic acid, phosphate, sugar, nucleotide, adenine, cytosine, thymine , guanine

 

Check Yourself: In our last class we:

Discussed whether or genetic code should be made available to everyone

 

*SOCIAL SCIENTIST ASSISTANCE!!

Warm Up:

What are the various parts of your DNA?

GENES CHROMOSOMES DNA for ALL!

DNA(Deoxyribonucleic Acid)

Genetic material of cells…Genetic material of cells…

• GENES – units of genetic material that GENES – units of genetic material that CODES FOR A SPECIFIC TRAITCODES FOR A SPECIFIC TRAIT

• Called Called NUCLEIC ACIDSNUCLEIC ACIDS

• DNA is made up of repeating molecules DNA is made up of repeating molecules called called NUCLEOTIDESNUCLEOTIDES

DNA NucleotideDNA Nucleotide

OO=P-O O

PhosphatePhosphate GroupGroup

NNitrogenous baseNitrogenous base (A, G, C, or T)(A, G, C, or T)

CH2

O

C1C4

C3 C2

5

SugarSugar(deoxyribose)(deoxyribose)

A HISTORY OF DNAA HISTORY OF DNA

• Discovery of the DNA double helixDNA double helix

A. Frederick Griffith – Discovers that a factor in diseased bacteria can transform harmless bacteria into deadly bacteria (1928)

B. Rosalind Franklin - X-ray photo of DNA.(1952)

C. Watson and Crick - described the DNA molecule from Franklin’s X-ray.(1953)

Watson & Crick proposed…Watson & Crick proposed…

•DNA had specific pairing between the DNA had specific pairing between the nitrogen bases:nitrogen bases:

ADENINEADENINE – – THYMINETHYMINE

CYTOSINECYTOSINE - - GUANINEGUANINE

•DNA was made of DNA was made of 22 long stands of long stands of nucleotides arranged in a specific way nucleotides arranged in a specific way

called the called the “Complementary Rule”“Complementary Rule”

DNA Double HelixDNA Double Helix

NitrogenousNitrogenousBase (A,T,G or C)Base (A,T,G or C)

““Rungs of ladder”Rungs of ladder”

““Legs of ladder”Legs of ladder”

Phosphate &Phosphate &Sugar BackboneSugar Backbone

DNA Double HelixDNA Double Helix

P

P

P

O

O

O

1

23

4

5

5

3

3

5

P

P

PO

O

O

1

2 3

4

5

5

3

5

3

G C

T A

Nitrogenous BasesNitrogenous Bases

• PURINESPURINES

1. Adenine (A)Adenine (A)

2. Guanine (G)Guanine (G)

• PYRIMIDINESPYRIMIDINES

3. Thymine (T)Thymine (T)

4. Cytosine (C)Cytosine (C) T or C

A or G

Chargaff’s RuleChargaff’s Rule

• AdenineAdenine must pair with ThymineThymine

• GuanineGuanine must pair with CytosineCytosine

• Their amounts in a given DNA molecule will be about the sameabout the same.

G CT A

BASE-PAIRINGSBASE-PAIRINGS

CG

H-bonds

T A

DNA Modeling Activity• Instructions

1. Line the borders of your strip of paper with circles (that are not touching and makes the paper look like a long domino)

(What do these colors on the outside of your DNA molecule represent?)

CONGRATULATIONS – YOU HAVE CREATED THE BACKBONE OF THE

DNA MOLECULE!

• 2. Draw pentagons closer to the middle and between each circle.

(What do these represent?)

• 3. Connect the circles on one side to the pentagons on the same side nearest them

Now write the story

• 4. Write the letters A, G, T, or C closer to the center (but not on center) and a little ahead of the Sugars on one side of your paper (in any order you choose)

(What do these letters represent?)

5. And connect them to the sugars

• 6. Now finish the code by writing in the corresponding nucleotide across from the ones you have chosen!

• 7. And connect G to C with three bonds and A to T with two bonds (Which type?)

(What type of bond do these lines represent?

• HW – bring in the (basic) material you need for a pilot run of your science fair project…

• Check power school and ensure you find the grade I have zeroed

Open NBK quiz (you have 5 minutes)

Directions: In your notebook, clearly ANSWER (only) the following questions.

1. What does DNA stand for? (1 pt)

2. What are the 3 parts of each nucleotide? (3 pts)

3. What are the different possible nitrogenous bases? (4 pts)

Objective: To learn about how DNA is replicated and transcribed

Genetic Diversity…Genetic Diversity…• Different Different

arrangements of arrangements of NUCLEOTIDESNUCLEOTIDES in a in a nucleic acid (DNA) nucleic acid (DNA) provides the key to provides the key to DIVERSITYDIVERSITY among among living organisms.living organisms.

The Code of Life…The Code of Life…

• The “code” of the chromosome is the The “code” of the chromosome is the SPECIFIC ORDERSPECIFIC ORDER that bases occur. that bases occur.

A T C G T A T G C G G…A T C G T A T G C G G…

DNA is wrapped tightly around histones and coiled tightly to form

chromosomes

DNA DNA ReplicationReplication• DNA must be copiedDNA must be copied

• The DNA molecule produces The DNA molecule produces 2 2 IDENTICALIDENTICAL new complementary new complementary strands following the rules of strands following the rules of base pairing: base pairing:

A-T, G-CA-T, G-C

•Each strand of the Each strand of the original DNA serves as original DNA serves as a template for the new a template for the new strand strand

DNA DNA ReplicationReplication

• Semiconservative Semiconservative Model:Model:

1. Watson and Crick Watson and Crick showed:showed: the two strands of the parental molecule separate, and each functions as a template for synthesis of a new complementary strand.

. Parental DNA

DNA Template

New DNA

Activity – Try it

1. Why is replication necessary?

2. When does replication occur?

3. Describe how replication works.

4. Use the complementary rule to create the complementary strand:

A---?G---?C---?T---?A---?G---?A---?G---?C---?A---?G---?T---?

Replication Quiz

1. Why is replication necessary?So both new cells will have the correct DNA2. When does replication occur?During interphase (S phase).3. Describe how replication works.Enzymes unzip DNA and complementary

nucleotides join each original strand.4. Use the complementary rule to

create the complementary strand:

A---TG---CC---GT---AA---TG---CA---TG---CC---GA---TG---CT---A

Replication Quiz

(1961)(1961) Watson & Crick proposed… Watson & Crick proposed…• ……DNA controlled cell function by DNA controlled cell function by

serving as a template for serving as a template for PROTEINPROTEIN structure.structure.

• 3 Nucleotides = a triplet or 3 Nucleotides = a triplet or CODONCODON(which code for a specific AMINO ACID)(which code for a specific AMINO ACID)

• AMINO ACIDSAMINO ACIDS are the building blocks are the building blocks of proteins.of proteins.

DNA DNA TranscriptionTranscription

• DNA can “unzip” DNA can “unzip” itself and itself and RNARNA nucleotides match nucleotides match up to the DNA up to the DNA strand.strand.

• Both DNA & RNA Both DNA & RNA are formed from are formed from NUCLEOTIDESNUCLEOTIDES and and are called are called NUCLEICNUCLEIC acids.acids.

DNA DNA and and RNARNA

DNADNA• C, G, A, T

– THYMINE

• Contained in the Nucleus

• Double Strand (more stable)

RNARNA• C, G, A, U

– URACIL

• Contained in the Nucleus and Cytoplasm

• Single Strand (less stable)

Activity – Try itRules- DNA is transcribed with the help of transcription

factors that bind to specific sites on the DNA- Transcription factors generally show where to start

or stop transcription

Our transcription factor will

1) initiate transcription at the 3rd, 4th and 5th nitrogenous base in your DNA

2)Terminate transcription at the 14th nitrogenous base

DNA DNA TranslationTranslation• Happens outside of the nucleus in the cytoplasmHappens outside of the nucleus in the cytoplasm• The cell uses information from “messenger” RNA The cell uses information from “messenger” RNA

to produce proteinsto produce proteins• Ribosomes help amino acids attach in anti-codon Ribosomes help amino acids attach in anti-codon

sequences to the mRNAsequences to the mRNA• The process is controlled by start and stop codesThe process is controlled by start and stop codes• Amino acids are the building blocks for proteinsAmino acids are the building blocks for proteins

IMAGES TO ASSIST

PRACTICESequence 1 – Human (template strand)

C T A C C A T A G C A C G T A A C G T AT C G G T A A

RNA :

Amino Acids:

G A UG G U A U C G U G C A UU G C A UAG C C A U U MET V A L S E R C Y S I LE A L A STOP

1. Find the start codon on your mRNA (AUG)

(If you do not have one or if it as the very end change your first three nitrogenous bases to AUG for this practice)

2. Start using the tRNA (little paper strips) for each codon and attach the amino acid (paper clips) to build your protein

3. Continue until you come to the STOP codon (UAG, UAA, UGA)

(if you do not have a stop codon then change the last codon to say UAG, UAA or UGA)

4. Record the amino acid sequence of your protein.

TRY IT

Transcription/Translation Quiz1. Why is transcription necessary?

2. Describe transcription.

3. Why is translation necessary?

4. Describe translation.

5. What are the main differences between DNA and RNA.

6. Using the chart on page identify the amino acids coded for by these codons:

UGGCAGUGC

1. Why is transcription necessary?Transcription makes messenger RNA (MRNA) to carry the code for proteins out of the nucleus to the ribosomes in the cytoplasm.

2. Describe transcription.

RNA polymerase binds to DNA, separates the strands, then uses one strand as a template to assemble MRNA.

3. Why is translation necessary?

Translation assures that the right amino acids are joined together by peptides to form the correct protein.

4. Describe translation.The cell uses information from MRNA to produce proteins.

5. What are the main differences between DNA and RNA.DNA has deoxyribose, RNA has ribose; DNA has 2 strands, RNA has one strand; DNA has thymine, RNA has uracil.

6. Using the chart on page 303, identify the amino acids coded for by these codons: UGGCAGUGCtryptophan-glutamine-cysteine

AMAZING DNA FACTS…AMAZING DNA FACTS…

• DNA from a single human DNA from a single human cell extends in a single cell extends in a single thread for almost 2 meters thread for almost 2 meters long!!!long!!!

• It contains information It contains information equal to some 600,000 equal to some 600,000 printed pages of 500 words printed pages of 500 words each!!! each!!! (a library of about 1,000 books)(a library of about 1,000 books)

You Tube Clip Links

• Replication• http://www.youtube.com/watch?v=vJSmZ3DsntU

• Transcription• http://www.youtube.com/watch?v=rpwjZX_z5rg&feature=

channel

• Translation• http://www.youtube.com/watch?v=SghWl3MVbAI

So now we’ve learned how to make proteins

• What do they do? • What are they good for?

•

1. MUTATIONS!

• This is when something goes wrong!!!

Point mutations:

Single base mutations:

1. Missense mutation: leads to an amino acid change

2. Silent mutation: does not change the amino acid

3. Nonsense mutation: causes premature stop-codon

• Frameshift mutations:

insertion/deletion

dublication

translocation

Altered reading frame Severe impacts on protein structure

Albinism - Mutation

Time for some DNA poetry

• Handout review• Follow-Up Assignment

– Write a very short story that consists of three letter words (5 to 15 words)

(why are we using three letter words?)- Modify your story using each type of mutation

(Point, frame shift, insertion, deletion, inversion)

WHEN ARE MUTATIONS HARMFUL?“HELPFUL?”“HAVE NO IMPACT?”

Let’s Make Paper Planes…http://www.zurqui.com/crinfocus/paper/air-bld1.html

• Connection – The SHAPE of the PROTEIN determines the function of the PROTEIN

• The shape of the plane determines the flight of the plane– Small changes in the shape of the plane may

• HAVE NO EFFECT (greatest majority)• HAVE A HARMFUL EFFECT• HAVE A BENEFICIAL EFFECT

(JUST LIKE MUTATIONS)