Chapter 12 n DNA DNA structure DNA replication

Overview A. Griffith and Transformation 1. Griffith’s Experiments 2. Transformation B. Avery and DNA

The Big Question n n Genetic information is in the nucleus of a cell.

1. Griffith’s Experiment (Transformation) Heat-killed, disease -causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies)

1. Griffith’s Experiment n Transformation ¨ To take in genetic material from an outside

2. Avery’s Experiment Removed chromosomal protein and DNA from heat-killed disease-causing bacteria. n Tried

3. Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium

DNA and Nucleotides DNA is made of four nitrogen-containing molecules called NUCLEOTIDES. n There

4. Chargaff discovers the percentage of bases in four organisms Source of DNA A

Watson and Crick Discovered the 3 D structure of DNA in 1953. n Used

n DNA is a Double Helix - like a twisted rubber ladder made from

n Consists of three parts: è Phosphate group (PO 43 -) è Deoxyribose (sugar)

DNA Nucleotides Purines Adenine Guanine Phosphate group Pyrimidines Cytosine Thymine Deoxyribose

Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine

The process of pulling the strands apart from each other and replacing each single

A DNA Helicase, an enzyme, separates the Hbonds in DNA into two strands.

DNA Polymerase attaches to separated parental strands and matches up free nucleotides New Daughter

DNA Replication New strand DNA polymerase Original strand DNA polymerase Growth Replication Nitrogen fork

Chromosome Structure Chromosome Nucleosome DNA double helix Coils Supercoils Histones

Homework SA 12 -1 all questions n SA 12 -2 all questions n Understand

If the DNA of one cell is stretched out, it makes a 7 ft.

Slides: 28

Download presentation

Chapter 12 n DNA ¨ DNA structure ¨ DNA replication

Overview A. Griffith and Transformation 1. Griffith’s Experiments 2. Transformation B. Avery and DNA C. The Hershey-Chase Experiment 1. Bacteriophages 2. Radioactive Markers D. The Structure of DNA 1. Chargaff’s Rules 2. X-Ray Evidence 3. The Double Helix E. Replication of DNA

The Big Question n n Genetic information is in the nucleus of a cell. It is in structures called chromosomes. Chromosomes are made of protein and DNA. Which organic molecule carries the genetic information? ¨ Protein ¨ DNA

1. Griffith’s Experiment (Transformation) Heat-killed, disease -causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria (smooth colonies) Dies of pneumonia Go to Section: Lives Control (no growth) Live, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumonia

1. Griffith’s Experiment n Transformation ¨ To take in genetic material from an outside source resulting in a change of function ¨ Griffith’s experiment was the earliest documented evidence of transformation

2. Avery’s Experiment Removed chromosomal protein and DNA from heat-killed disease-causing bacteria. n Tried to transform living non-deadly bacteria by using protein or DNA. n Only DNA worked. n Showed that DNA is necessary for a successful transformation. n

3. Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

DNA and Nucleotides DNA is made of four nitrogen-containing molecules called NUCLEOTIDES. n There are four different nucleotides in DNA: n ¨ Thymine (T) ¨ Adenine (A) ¨ Cytosine (C) ¨ Guanine (G)

4. Chargaff discovers the percentage of bases in four organisms Source of DNA A T G C Streptococcus 29. 8 31. 6 20. 5 18. 0 Yeast 31. 3 32. 9 18. 7 17. 1 Herring 27. 8 27. 5 22. 2 22. 6 Human 30. 9 29. 4 19. 9 19. 8

Two WEAK H -Bonds Three WEAK HBonds

Purine Bases Pyrimidine Bases

Watson and Crick Discovered the 3 D structure of DNA in 1953. n Used knowledge of physical chemistry, structural components of DNA, x-ray diffraction photos, and guesswork. n

n DNA is a Double Helix - like a twisted rubber ladder made from three main components: Sides of the ladder are composed of alternating sugar and phosphate pieces Each “rung” of the ladder is made up of two complementary bases n A bound to T C bound to G DNA is put together in chunks called NUCLEOTIDES

n Consists of three parts: è Phosphate group (PO 43 -) è Deoxyribose (sugar) è a nitrogen-containing base

DNA Nucleotides Purines Adenine Guanine Phosphate group Pyrimidines Cytosine Thymine Deoxyribose

Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

The process of pulling the strands apart from each other and replacing each single strand with its complement (pair) is called REPLICATION

A DNA Helicase, an enzyme, separates the Hbonds in DNA into two strands.

DNA Polymerase attaches to separated parental strands and matches up free nucleotides New Daughter Strand

DNA Replication New strand DNA polymerase Original strand DNA polymerase Growth Replication Nitrogen fork bases Replication fork New strand Original strand

Chromosome Structure Chromosome Nucleosome DNA double helix Coils Supercoils Histones

Homework SA 12 -1 all questions n SA 12 -2 all questions n Understand n ¨ the early experiments (look at pictures) ¨ Structure DNA (phosphate, sugar, bases…) ¨ DNA replication

If the DNA of one cell is stretched out, it makes a 7 ft. long string In mammalian cells, there is one mistake in one billion during replication There about 5 trillion cells in the human body It takes 50 -500 nucleotides per second to replicate DNA If you connected all the DNA together, it would be long enough that it would take over 10 hours to travel its length at light speed There are 10. 4 bases in one full turn