History of DNA DNA Discovery RNA Transcription Translation Mutations

History of DNA DNA Discovery RNA Transcription Translation Mutations
DNA & RNA Units of Life History of DNA DNA Discovery RNA Transcription Translation Mutations

DNA: Blueprint for Life
A. History of Discovery Frederick Griffith: Mice Transformation Avery: DNA Identified Hershey-Chase: DNA and Viruses Rosalind Franklin: X-ray Evidence Chargaff’s Rules: Base Pairing Watson and Crick:The Double Helix

Discovery of DNA: A History
FREDERICK GRIFFITH (1928) Studied way in which bacteria cause pneumonia and recognized process of transformation. Showed through experiments that one strain of bacteria could be transformed into another. Hypothesized that there was a transforming factor involved.

Griffith’s Experiment
Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)

Griffith’s Experiment
Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Control (no growth) Harmless bacteria (rough colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)

DNA Discovery: A History
AVERY (1944) Repeated Griffith’s experiments and identified DNA as the transforming factor-identified DNA DNA-stores and transmits genetic information from one generation to another.

HERSHEY-CHASE (1952) Experiments with bacteria-killing viruses (bacteriophages) Confirmed again that DNA was the molecule that contained the genetic code.

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

ROSALIND FRANKLIN and MAURICE WILKINS (1950’S) Studied DNA molecule by using a purified DNA sample and x-ray pictures of molecule. Found it was a twisted “X” structure.

ERWIN CHARGAFF (early 1950’s) Observed in any DNA sample, the number of adenine molecules was equal to the number of thymine; same for guanine and cytosine. Developed nitrogen base pairing rules

Percentage of Bases in Four Organisms
Source of DNA A T G C Streptococcus Yeast Herring Human

WATSON-CRICK (1953) Tried to build 3D DNA model -couldn’t quite solve it Used Franklin’s pictures to develop the double helix model Double helix model explained much about DNA structure, including placement of nitrogen bases and the formation of bonds. Received Nobel Prize along with Wilkins (Franklin didn’t—why?)

DNA: Blueprint for Life
B. The Structure of DNA 1. Nucleotides – basic unit of DNA 2. Nitrogen Bases 3. DNA Replication

Structure of DNA DNA made of nucleotides, the basic unit
Nucleotide is made of three parts: 1. One Phosphate 2. One 5-Carbon Sugar (deoxyribose) 3. One Nitrogen base Adenine(A), Guanine(G) – Purines Thymine(T), Cytosine(C) – Pyrimidines

Structure of DNA Sugar and Phosphate are the “backbone” of DNA
Two parallel strands of sugar-phosphate groups with pairs of nitrogen bases linking the two strands together with weak hydrogen bonds, forming a double helix. WHY WEAK BONDS?

Structure of DNA Nitrogen Base Pairing ‘Rulz’:
A=T (one purine/ pyrimidine) C=G (one purine/ pyrimidine) DNA strands are complementary because of base pairing rules Nitrogen bases attached to sugars.

DNA Nucleotides Purines Pyrimidines Phosphate group Deoxyribose
Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose

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

DNA Replication A Perfect Copy
When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

DNA Replication Complementary strands of DNA serve as a pattern for a new strand. DNA replication carried out by enzymes which “unzip” the two strands by breaking the hydrogen bonds. Then, appropriate nitrogen bases are inserted. Enzymes also proofread the bases to make sure of correct base pairing (called DNA polymerases).

Chromosome Structure Nucleosome Chromosome DNA double helix Coils
Supercoils Histones

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

DNA Replication Copied DNA C G G T A A C A T T A
DNA G C C A T T G T A A T enzymes Copied DNA C G G T A A C A T T A DNA G C C A T T G T A A T

RNA: The Other Code C. RNA and Protein Synthesis
A.The Structure of RNA B. DNA and RNA Similarities/Differences C. Transcription D. Types of RNA Protein Synthesis F. Translation

RNA: The Other Code A. RNA similar to DNA
long chain made of nucleotides each nucleotide consists of: a sugar a phosphate a nitrogen-containing base sugar and phosphate still backbone of RNA

RNA: The Other Code B. RNA different from DNA
• Different type of sugar (ribose) • Single strand rather than a double strand RNA molecule is a disposable copy of DNA • Nitrogen base THYMINE found in DNA replaced by a similar base URACIL (U) in RNA ex. ( A - U ) and ( C - G )

Why RNA? C. Why does DNA need to transfer genetic information to RNA?
1. DNA is found in the nucleus. Ribosomes are outside the nucleus. 2.DNA does not leave nucleus-too large for nuclear pores. 3.Messenger must bring genetic information from the DNA to the ribosomes to make proteins/amino acid 4.Special molecule, messenger RNA (mRNA), performs this task.

RNA: The Other Code RNA - The Other Part of the Code
RNA –“messenger” between the DNA in the nucleus and the ribosomes. (mRNA) Ribosomes –organelles outside the nucleus that make proteins from amino acids. Proteins/Amino Acids –used to build and repair cells.

RNA Synthesis Transcription- process by which one strand of DNA is copied into a complementary strand of mRNA in the nucleus. mRNA C G G U A A C A U U A enzymes DNA G C C A T T G T A A T enzymes Copied DNA C G G T A A C A T T A enzymes mRNA G C C A U U G U A AU

Transcription RNA polymerase DNA RNA Adenine (DNA and RNA)
Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA

Types of RNA Transfer RNA (tRNA) A. Carries amino acids to ribosome
B. Single strand looped back on itself C. Anticodon-three nucleotides on tRNA are complementary to the three on the mRNA. D. Matching of codon (mRNA) to anticodon (tRNA) allows the correct amino acid to be put in place. Ribosomal RNA (rRNA) A. makes up majority of ribosome

Bring amino acids to ribosome
Types of RNA RNA can be Messenger RNA Ribosomal RNA Transfer RNA also called which functions to also called which functions to also called which functions to mRNA Carry instructions rRNA Combine with proteins tRNA Bring amino acids to ribosome from to to make up DNA Ribosome Ribosomes

Protein Synthesis A. Nucleotides in DNA have all the information to make proteins. B. DNA code copied into mRNA C. Proteins are made of amino acids which are coded from mRNA. D. mRNA code is read in triplet form called a CODON which specifies certain amino acids using a decoder (p.201)

Protein Synthesis: Translation
Only 20 amino acids make all life as we know it! How can this be? *AUG - codes for amino acid methionine or be an “initiator codon” and will always start mRNA *Some are “stop” codons which end mRNA Translation -the decoding of mRNA code into an amino acids--proteins

Translation mRNA Nucleus Messenger RNA mRNA Lysine Phenylalanine tRNA
Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA Transfer RNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Methionine Ribosome mRNA Start codon

Translation (continued)
The Polypeptide “Assembly Line” The ribosome joins the two amino acids—methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome

The Genetic Code Decoder
BACK

Translation DNA T A C T T T G T A A C T mRNA A U G A A A C A U U G A
enzymes mRNA A U G A A A C A U U G A

Determining the Sequence of a Gene
DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

Mutations Mutations can occur on individual chromosomes by way of gene mutations. Base sequence gets rearranged and may cause insertion, deletion, or substitution of genes Mutations can also occur with entire chromosomes.

Gene Mutations: Substitution, Insertion, and Deletion

Chromosome Mutations Deletion Duplication Inversion Translocation

Impact of Genetics Autosome Disorders caused by Recessive alleles
Dominant alleles Codominant alleles include include include Albinism Galactosemia Tay-Sachs disease Huntington’s disease Sickle cell disease Cystic fibrosis Phenylketonuria Achondroplasia Hypercholes- terolemia

Pedigrees A circle represents a female. A square represents a male.
A horizontal line connecting a male and female represents a marriage. A vertical line and a bracket connect the parents to their children. A half-shaded circle or square indicates that a person is a carrier of the trait. A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait. A completely shaded circle or square indicates that a person expresses the trait.

Blood Groups A. Four major blood groups: A, B, O, AB
B. Each type carries certain Antigens C. Antigens are markers on surface of cells that identify the type of cell. Allows antibodies to attack if they aren’t identified correctly. D. Antibodies found in the body, they provide protection from diseases and foreign substances. As you are exposed to diseases, your body builds up antibodies—resistance.

Blood Groups E. Blood Type Antigen Antibodies
A A b B B a AB AB none O none a and b F. Type O blood is the universal donor blood Why? There are no markers (but O can only receive O) G. Type AB is the universal recipient blood Why? Carry both markers; lack antibodies

Blood Groups Safe Transfusions Phenotype (Blood Type Antigen on
Red Blood Cell Genotype To From

Blood Groups-Rh Factor
Rh factor identified in rhesus monkey and later found in human blood. Rh+ is dominant over Rh- If you have Rh+ blood (O+, A+, etc)= O+O+, A+O- , B+O+, etc If you have Rh- blood (O-, B-, etc)= O-O-, B-O- ,A-O- , etc

Blood Types-Rh Factor Blood types must match up correctly when getting blood or death results. Important during pregnancy: if mom is Rh- and has Rh+ fetus, mom’s antibodies don’t recognize Rh+ and begin to attack. Could result in death. This can be detected early and treated with blood supplements. What was the dad’s Rh type?

Homologous chromosomes fail to separate
Nondisjunction Homologous chromosomes fail to separate Meiosis I: Nondisjunction Meiosis II

Sex-Linked Traits: Colorblindness
Father (normal vision) Normal vision Colorblind Male Female Daughter (normal vision) Son (normal vision) Mother (carrier) Daughter (carrier) Son (colorblind)

History of DNA DNA Discovery RNA Transcription Translation Mutations

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