DNA

Hmwk: take notes for an open note quiz

• p. 287-290

• Focus: Who did the experiment?• What did they do? What did they

conclude? Key words/vocabulary.

Open note quiz p. 287-290

• 1. What disease was Griffith studying?

• 2. What did Griffith call the process by which the harmless bacteria became harmful?

• 3. What was the purpose of Avery in repeating Griffith’s experiment? In other words, what did he want to know?

• 4. What was the conclusion of Avery’s experiment?

• 5. A virus that infects bacteria is called a:

• 6. What did Hershey & Chase use to track DNA and proteins?

Big ideas

• Living systems store, retrieve, transmit and respond to information essential to life processes.

• Biological systems interact, and these systems

and their interactions possess complex properties.

Essential knowledge

• DNA and in some cases RNA, is the primary source of heritable information– Genetic information is stored in and passed to

subsequent generations through DNA molecules– The proof that DNA is the carrier of genetic

information involved a number of historical experiments: Watson, Crick, Franklin, Wilkins, Griffeth, Avery

Essential knowledge continued

• DNA is composed of sugar, phosphate and nitrogen base, which form nucleotides

• DNA is held together by covalent bonds and hydrogen bonds

• DNA is antiparallel and double stranded• DNA exhibits base pairing that is conserved

through evolution : A-T and G-C (Chargoff’s rule)

Essential knowledge continued

• Purines & Pyrimidines differ in their carbon rings

Learning outcomes

• Be able to explain the experiments &

conclusions of Griffeth and Avery’s research using Pneumococcus & mice.

• Identify the 3 subunits of DNA & describe how they are put together to construct an intact molecule.

Learning outcomes continued.

• Understand the importance of Chargoff’s rules & the complementary nature of base pairing.

• Describe Watson & Crick’s 3 dimensional model based the evidence provided by Rosalind Franklin.

1. What is DNA?

• 2. Deoxyribonucleic Acid

*. a chemical that stores genetic information

*. the instructional material of chromosomes

* Blueprint of life

Griffith’s experiment

1. What experiments lead scientists to believe DNA was the

“genetic material”? (read 287-290)

2. Griffith’s Transformation experiment 1928

* concluded: Streptococcus bacterial cells can pick up “free” genetic information

* Griffith did not know the “free stuff” was DNA.

Hypothesis: Material from dead cells can genetically transform live bacterial cells.

Conclusion: A chemical substance from dead cells can genetically transform live cells.

2. Avery– 1944

* used the same Streptococcus bacteria strains (S & R) –

*stripped dead S (smooth virulent strain) of protein

*R (rough non-virulent) still transformed

2. Hershey and Chase experiment

* Use radioactive markers to follow proteins & DNA

•conclusion: DNA enters Bacteria-

DNA is geneticmaterial

Animation

Quick check

• 1. What is DNA?

• 2. Describe the 2 strains of bacteria used by Griffith.

• 3. What did Griffith do to the “deadly” bacteria in the experiment?

• 4. What happened to the “good” bacteria when mixed with the “deadly” solution?

• 5. Explain what is meant by “transformation” with regard to the experiment.

• 6. How did Avery alter Griffith’s experiment? What did he want to know that Griffith could not conclude?

• 7. Explain how Avery was able to conclude that DNA was the chemical that the bacteria picked up and transformed them.

• 8. Explain how Hershey & Chase determined that DNA entered the cell from the virus.

What has knowing about DNA done for us?

Genetic disease knowledge/treatments

Identification of unknowns: military, 911, abductions

Exoneration from prison/ sentencing for prison

1. What is DNA’s structure?

2. DNA structure:

*made of monomers called nucleotides

* nucleotides are made of: -5 Carbon sugar (deoxyribose)

- phosphate group (PO4)

- nitrogen base

Quick check

2. Nitrogen bases are specifically paired

- Adenine –Thymine (2 H bonds)

- Guanine – Cytosine ( 3 H bonds)

2. Nitrogen bases are grouped as

*purines (double carbon rings): adenine & guanine

*pyrimidines (single carbon rings)cytosine & thymine

Quick check

2. DNA is double stranded helix, with anti-parallel strands

* 3’- 5’ strand

* 5’- 3’ strand

2. Phosphodiester bonds hold one nucleotide to another –

Extract DNA

Lab:

• Use the knex to build a DNA model. Will do tomorrow and 12.3

• Also assign a model making project… I like the toothpick or bead activity.

Quick check

2. Nitrogen bases are specifically paired

- Adenine –Thymine ( __ H bonds)

- Guanine – Cytosine ( __ H bonds)

2. __________ bases are grouped as

*purines (________ carbon rings): adenine & guanine

*pyrimidines (________ carbon rings)cytosine & thymine

Quick check

Quick check

1. How was the structure of DNA identified?

2. Erwin Chargoff: *Chargoff’s rule : The proportion of adenine equals that of thymine, and guanine equals that of cytosine -- therefore, purines are proportionate to pyrimidines

2. Rosalind Franklin:

* Used X-ray diffraction to determine 3 dimensional structure of DNA ---

worked with Maurice Wilkins

Photo 51

2. James Watson & Francis Crick:

*Used everyone else’s puzzle pieces (research) to build a model of DNA’s structure -- 1953 --- won Nobel Prize

• 2. Linus Pauling - 2 time Nobel Prize winner..... COMPETITION!!!!

Video: Life story

• 20 minute recap of how DNA structure was identified.

• P. 355-357 DNA fingerprinting

1. What is DNA fingerprinting and what can we learn from it?

• What is DNA fingerprinting?• - a method used to identify individuals based

on unique fragments of DNA (RFLP, VNTR, STR)

Secrets of the sequence- DNA/profiling

http://video.vcu.edu/vod/sosq/sosq_115_1.mp4

Timeline

• Day: What is DNA & why is it important? & Experiments that identified DNA as the genetic stuff.

• Day: What is DNA’s structure/function? Lots of modeling, examples etc…. Provide directions for building a DNA model at home.

• Day : Extract DNA (thymus, cheek cells, kiwi)

• Day: Build DNA model knex

• Day : Notes history of DNA/video clip…

• Day: DNA fingerprinting notes / online lab