AP Biology Unit 6 Student Notes

Table of Contents Link Unit 6 Gene Expression and Regulation Student Notes Page 1

AP Biology Unit 6

Student Notes

Table of Contents Link Unit 6 Gene Expression and Regulation Student Notes Page 2

Unit 6 Student Notes

Table of Contents

A. History of DNA Research --Pages 3-10

B. Proteins or DNA: Which is the Genetic Molecule--Page 3-6

C. DNA Structure--Pages 8-11

D. DNA Replication--Pages 11-15

E. Telomeres--Pages 15-17

F. The Central Dogma of Genetics--Page 17

G. Transcription--Pages 18-21

H. RNA Processing--Pages 21-23

I. Alternative Splicing--Page 22

J. Types of RNA--Page 23

K. Differences Between DNA and RNA--Pages 24-25

L. Translation--Pages 26-31

M. Genetic Code Table--Page 26

N. Genetic Code Wheel--Page 25

O. tRNA--Page 27

P. Ribosomes--Page 28

Q. Three Stages of Translation--Pages 28-31

R. Wobble Effect--Pages 31-32

S. Post-Translation Modification or Protein Folding--Pages 32-33

T. Mutations and Genetic Disorders--Pages 33-35

U. Mutations and Natural Selection--Pages 35-36

V. Other Mechanisms that Can Change the Genotype and/or Phenotype of a Cell /Organism--

Pages 36-37

W. Gene Regulation--Pages 38-33

X. Operons--Pages 38-41

Y. Gene Regulation in Eukaryotic Cells--Pages 41-44

Z. Epigenetics--Page 43

AA.

Embryonic Development--Pages 44-46

BB.

Hox Genes--Pages 46-47

CC.

DNA Biotechnology--Pages 47-57

DD.

Possible Applications of Biotechnology and Recombinant DNA--Page 47-48

EE.

DNA Cloning--Pages 48-50

FF.

Polymerase Chain Reaction (PCR)--Pages 50-53

GG.

Gel Electrophoresis--Pages 53-55

HH.

DNA Sequencing/Human Genome Project--Page 56

II. Gene Editing/CRISPR/CAS9--Pages 56-57

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Key Ideas/Enduring Understandings for Unit 6 Heritable information provides for the continuity of life. Differences in the expression of genes account for some of the phenotypic differences between organisms. The processing of genetic information is imperfect and is a source of genetic variation.

Introduction Scientists now know that DNA, and in some cases RNA, is the primary source of genetic/heritable information in all life forms. This genetic information is both stored and transmitted from one generation to the next through either DNA or RNA molecules. The DNA of a prokaryotic cell is typically packaged in a single, circular chromosome, while in a eukaryotic cell, the DNA is typically contained in multiple linear chromosomes. Prokaryotes (and some eukaryotes) can also contain plasmids, which are small extra-chromosomal, double-stranded, circular DNA molecules. The "History of DNA Research" note section (included below) will describe how scientists were able to determine that DNA and RNA serve as the sources of heritable information storage and transfer.

History of DNA Research

Gregor Mendel (in 1866) Mendel, an Australian monk, worked with pea plants to discover the basic laws of inheritance.

Friedrich Miescher (in 1869) Miescher, while trying to isolate proteins from white blood cells, discovered a chemical which he called nuclein. Today, that chemical is known as DNA.

Proteins or DNA: Which is the Genetic Molecule? For several years after Miescher's discovery, the importance of DNA was not understood. Most scientists believed that proteins served as the genetic molecules of cells. That made sense because scientists already understood that proteins were built from several kinds of amino acids (20). This, they thought, could explain the genetic diversity of life. DNA, on the other hand, was built from only 4 nitrogenous bases. Scientists didn't think that DNA could code for the diversity of traits found across life. Experiments in the early 1900s eventually proved that DNA, not protein, was the genetic molecule.

Frederick Griffith (in 1928) Griffith was a British Army doctor who was studying Pneumonia in the hopes of finding a cure. He is given credit for the transformation experiment, even though this was not his original intent. In the experiment, he took pathogenic (disease causing) bacteria and non-pathogenic bacteria and injected them into mice. The pathogenic bacteria killed the mice. The non-pathogenic did not. He then took some pathogenic bacteria and killed them by exposing them to heat. He took the dead bacteria and injected them into more mice. The mice did not die. He then took some of the dead pathogenic bacteria and mixed them with living non-pathogenic bacteria. He then injected the mixture into mice. The mice died. His reasoning was some "instructional agent" was exchanged between the dead pathogenic bacteria and the living non-pathogenic bacteria allowing them to "learn" a new trick. The non-pathogenic bacteria were transformed from non-pathogenic into pathogenic bacteria. Griffith was never able to determine which molecule acted as the "instructional agent" that allowed the transformation to take place.

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Oswald Avery and associates (in 1944) Avery and his associates repeated Griffith's experiments with the purpose of identifying what the "instructional agent" was that led to the transformation of the non-pathogenic bacteria. He was able to show that the transformation agent was DNA. The results of the experiment sparked lots of controversy, because most scientists still thought that DNA was too simple to act as the genetic molecule and that proteins must play that role. The experiment did create some doubt and it inspired other researchers to more closely examine the issue.

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Alfred Hershey and Martha Chase (in 1952) Hershey and Chase worked with the T2 Bacteriophage (a virus that infects bacteria) and E. Coli bacteria. They wanted to definitively identify if protein or DNA served as the genetic material. Bacteriophages were perfect for the task because they consist of only DNA and proteins. The researchers used radioactive Sulfur 35 to label the virus's outer protein coat or capsid. Proteins, because of the amino acid Cysteine, contain sulfur. DNA does not. Hershey and Chase were able to use the radioactivity to follow where the proteins went during the experiment. In a second experiment, they then used radioactive Phosphorus 32 to label the DNA inside the virus. DNA contains phosphorus, while proteins do not. The radioactively labeled viruses were exposed to bacteria. The viruses infected the bacteria. In the radioactive Sulfur experiment, the radioactive sulfur did NOT enter the bacteria. When the viruses reproduced inside the bacteria, the new viruses that came out of the dead bacteria were NOT radioactive. In the radioactive Phosphorus experiment, the radioactive phosphorus did enter the bacteria. When the viruses reproduced inside the bacteria, the new viruses that came out of the dead bacteria WERE radioactive. The experiment showed that viruses attack bacteria by injecting their DNA, not their proteins, into the bacterial cells. This proved to most scientists that DNA was the "transformation agent" and that DNA carries the information "blueprint" from one generation to the next.

Bacteriophage

Hershey and Chase Experiment

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