DNA & RNA Units of Life
-
Upload
nathaniel-gates -
Category
Documents
-
view
20 -
download
1
description
Transcript of DNA & RNA Units of Life
DNA & RNAUnits of Life
A. History of DNAB. DNA DiscoveryC. RNAD. TranscriptionE. TranslationF. Mutations
DNA: Blueprint for Life
A.History of Discovery1. Frederick Griffith: Mice
Transformation2. Avery: DNA Identified3. Hershey-Chase: DNA and Viruses4. Rosalind Franklin: X-ray Evidence5. Chargaff’s Rules: Base Pairing6. 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
Disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth colonies)
Control(no growth)
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)
Dies of pneumonia
Section 12-1
Griffith’s Experiment
Disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough
colonies)
Heat-killed, disease-causing bacteria (smooth
colonies)
Control(no growth)
Heat-killed, disease-causing bacteria (smooth colonies)
Harmless bacteria (rough colonies)
Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)
Dies of pneumonia
Section 12-1
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.
DNA Discovery: A History
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 infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Hershey-Chase Experiment
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Hershey-Chase Experiment
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
DNA Discovery: A History
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.
DNA Discovery: A History
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 CSource 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
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
DNA Discovery: A History
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 DNA1. Nucleotides – basic unit of DNA2. Nitrogen Bases3. DNA Replication
Structure of DNA
DNA made of nucleotides, the basic unitNucleotide is made of three parts:1. One Phosphate2. 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 NucleotidesPurines Pyrimidines
Adenine Guanine Cytosine Thymine
Phosphate group Deoxyribose
Structure of DNA
Weak Hydrogen bonds
Nucleotide
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.
Chromosome Structure
Chromosome
Supercoils
Coils
Nucleosome
Histones
DNA
double
helix
Growth
Growth
Replication fork
DNA polymerase
New strand
Original strand DNA
polymerase
Nitrogenous bases
Replication fork
Original strand
New strand
DNA Replication
DNA Replication
DNA G C C A T T G T A A T Copied DNA C G G T A A C A T T A
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 SynthesisA.The Structure of RNAB. DNA and RNA
Similarities/DifferencesC. TranscriptionD. Types of RNAE. Protein SynthesisF. 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 CodeA.RNA –“messenger” between
the DNA in the nucleus and the ribosomes. (mRNA)
B.Ribosomes –organelles outside the nucleus that make proteins from amino acids.
C. 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.
DNA G C C A T T G T A A TCopied DNA C G G T A A C A T T A
mRNA C G G U A A C A U U A
mRNA G C C A U U G U A AU
enzymes
enzymes
enzymes
Transcription
RNADNA
RNApolymerase
Adenine (DNA and RNA)Cystosine (DNA and RNA)Guanine(DNA and RNA)Thymine (DNA only)Uracil (RNA only)
Types of RNA
Transfer RNA (tRNA)A. Carries amino acids to ribosome B. Single strand looped back on itselfC. 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
Types of RNA
from to to make up
also called which functions to also called also called which functions towhich functions to
can be
RNA
Messenger RNA Ribosomal RNA Transfer RNA
mRNA Carry instructions rRNACombine
with proteins tRNABring
amino acids toribosome
DNA Ribosome Ribosomes
Protein Synthesis
A. Nucleotides in DNA have all the information to make proteins.
B. DNA code copied into mRNAC. 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
TranslationMessenger RNA
Messenger RNA is transcribed in the nucleus.
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.
mRNA Start codon
Ribosome
Methionine
Phenylalanine tRNALysine
Nucleus
mRNA
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.
mRNARibosome
Translation direction
Lysine tRNA
tRNA
Ribosome
Growing polypeptide chain
mRNA
Completing the PolypeptideThe process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain.
The Genetic Code Decoder
BACK
Translation
DNA T A C T T T G T A A C TmRNA A U G A A A C A U
U G A
enzymes
Determining the Sequenceof 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
Substitution InsertionDeletion
• Original The fat cat ate the wee rat.
• Point Mutation The fat hat ate the wee rat.• Frame Shift The fat caa tet hew eer at.• Deletion The fat __ ate the wee rat.• Insertion The fat cat xlw ate the wee rat• Inversion The fat tar eew eht eta tac.
Chromosome Mutations
Deletion
Duplication
Inversion
Translocation
Mutagen.
• Ultraviolet light, nuclear radiation, and certain chemicals can damage DNA by altering nucleotide bases so that they look like other nucleotide bases
Environmental Impact
• Ultraviolet light, nuclear radiation, and certain chemicals can damage DNA by altering nucleotide bases so that they look like other nucleotide bases.
Mutagens are environmental agents that can cause mutations in the genetic code.
• High energy radiation from radioactive elements, X-rays, gamma rays, microwaves, and ultraviolet light (please use sunscreen and wear a hat).
• Industrial chemicals such as PCB's (support the ban).
• Pollutants such as cigarette smoke (please don't smoke and if you do work hard to quit)
• Pesticides (eat organic).
• Food Additives (read food labels).
• Drugs (use only when necessary).
• Viruses (wash your hands and practice safe sex).
Mutagen
• An agent, such as a chemical, ultraviolet light, or a radioactive element, that can induce or increase the frequency of mutation in an organism.
• Spontaneous DNA replication and repair errors, spontaneous modification of nucleotides
• All types of mutations produced UV irradiation
• Pyrimidine dimers induce error prone repair (SOS) Mainly G-C to A-T transitions, but all other types of mutations including deletions, frameshifts, and rearrangements
Impact of Genetics
caused by
includeincludeinclude
AutosomeDisorders
Recessive alleles
Dominant allelesCodominant
alleles
Albinism Galactosemia Tay-Sachs disease
Huntington’s disease
Sickle cell disease
Cystic fibrosis
Phenylketonuria AchondroplasiaHypercholes-
terolemia
Pedigrees
A completely shaded circle or square indicates that a person expresses 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 half-shaded circle or square indicates that a person is a carrier of the trait.
A horizontal line connecting a male and female represents a marriage.
A circle represents a female.
A square represents a male.
A vertical line and a bracket connect the parents to their children.
Blood Groups
A. Four major blood groups: A, B, O, AB
B. Each type carries certain AntigensC. 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 GroupsE. Blood Type Antigen Antibodies A A b
B B aAB AB noneO 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
Phenotype(Blood Type Genotype
Antigen on Red Blood Cell
Safe Transfusions
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?
NondisjunctionHomologous
chromosomes fail to
separate
Meiosis I:Nondisjunction
Meiosis II
NondisjunctionHomologous
chromosomes fail to
separate
Meiosis I:Nondisjunction
Meiosis II
NondisjunctionHomologous
chromosomes fail to
separate
Meiosis I:Nondisjunction
Meiosis II
Sex-Linked Traits: Colorblindness
Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Male
Female
Sex-Linked Traits: Colorblindness
Father(normal vision)
ColorblindNormal vision
Mother (carrier)
Daughter(normal vision)
Son(normal vision)
Daughter(carrier)
Son(colorblind)
Male
Female