Introduction The Central Dogma of Molecular Biology

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IntroductionThe Central Dogma of Molecular
Biology
Cell
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DOGMA?

• This central dogma was develop by Crick.
• This was a hypothesis on how the code was read
  from DNA then used to make proteins. Scientists
  did not like this term for this hypothesis
  because it sounds like a problem!

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DOGMA!

• Principle, idea, or statement that is considered
  to be absolutely true. Kind of like a
  theory!!!!! But Crick called it a DOGMA!!!
• DNA ---- RNA ----- Proteins!!!!!!

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Central Dogma of Biology

• The flow of information in the cell starts at
  DNA,

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How does DNA determine what you look like?
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What is the purpose for proteins?

• antibody fight diseases
• Muscle contractions
• Enzymes
• Hormones
• Hair, feathers, beaks, nails, horns, etc.
• Egg whites
• Transport proteins blood(hemoglobin)

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Protein Structure

• Made up of amino acids
• Polypeptide- string of amino acids
• ONLY 20 amino acids are arranged in different
  orders to make a variety of proteins!!!! Amino
  acids are in the cytoplasm.
• Assembled on a ribosome

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DNA vs. RNA

• DNA
• Double Helix
• Deoxyribose sugar
• Adenine pairs with Thymine (A-T)
• Stays in nucleus

• RNA
• Single strand
• Ribose sugar
• Uracil replaces Thymine!
• Leaves nucleus to do the work

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DNA vs. RNA

• DNA RNA
• Deoxyribose Ribsose
• Thymine Uracil is one of the bases in
  RNA. There is thymine no thymine.
  This means A goes with U and G still
  goes with C.
• Double Strand Single Strand

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Steps to Protein Synthesis

• Transcription process where DNA message is
  changed into mRNA then out of nucleus to the
  ribosomes!!!
• 2. Translation process when mRNA is translated
  into amino acid chains(protein) on the ribosomes.

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How does a protein get built??

• This is where RNA becomes involved.
• DNA is too large to get out of the nuclear
  membrane pores.
• SO RNA has to be made to go to the ribosomes!!!

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SO, HOW DOES AN AMINO ACID CHAIN GET BUILT?
RNA stands for ribonucleic acid
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Stars of Translation and Transcription

1. mRNA
2. DNA
3. rRNA
4. tRNA
5. Ribsomes
6. RNA polymerase

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Three types of RNA

• 1. mRNA
• messenger RNA
• Carries code for proteins from DNA
• Carries codon

• 2. tRNA
• transfer RNA
• Attaches specific Amino Acids to the protein
  chain by matching the mRNA codon with the
  anticodon.

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RNA TRANSCIPTION
There are three (3) types RNA
1. Messanger RNA (mRNA) carries messages from
the DNA in the nucleus to the ribosomes.
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tRNA

• 2. Transfer RNA (tRNA) 20 different kinds
  which are only able to bond with one (1) specific
  type of amino acid.

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rRNA

• 3. Ribosomal RNA (rRNA) major component (part)
  of the ribosomes

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3. Ribosomal RNA rRNA

• Where Protein synthesis occurs

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How Does RNA polymerase(complex) know where to
start and stop?

• Promoter site starting point on DNA. Specific
  base sequences that represents a gene.
• Termination site Place where RNA polymerase
  stops!!!
• REMEMBER - only a gene is being read to make mRNA
  not all of your DNA.

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Step 1

• RNA polymerase complex attaches to DNA at special
  places that serve as the start signal(promoter
  sites). Only one gene!!!!!

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Step 2

• DNA splits at site of RNA polymerase.
• RNA polymerase attaches matching bases to form
  new RNA strand from DNA template.

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• RNA polymerase keeps adding bases making the RNA
  strand grow

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Step 3

• RNA polymerase leaves DNA when reaches the stop
  signal.
• RNA strand is released and goes to cytoplasm.
• DNA rewinds itself into the double helix.

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Results of Transcription

• Strand of mRNA made from the DNA

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FYI

• RNA polymerase doesnt check for mistakes in the
  code. Doesnt cause mutations when there is a
  few mistakes in proteins unlike replication.

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Protein Synthesis Transcription
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Making mature mRNA

• Original mRNA transcribed
• is not mature mRNA
• Exonsreadable segments
• Of mRNA that go to the
• ribsome
• Introns nonreadable
• Segments that must be removed before leaving
• Nucleus.

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Exons vs. Introns
Once introns removed, mRNA is ready to leave the
nucleus!!!!
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Eukaryotic Transcription
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Prokaryotic Protein Synthesis

• All occurs in the cyotplasm!!!

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Transcription is donewhat now?

• Now we have mature mRNA transcribed from the
  cells DNA. It is leaving the nucleus through a
  nuclear pore. Once in the cytoplasm, it finds a
  ribosome so that translation can begin.

• We know how mRNA is made, but how do we read
  the code?

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Translation

• Translation is the process of decoding a mRNA
  molecule into a polypeptide chain or protein.
• ALWAYS read mRNA!!!!!!
• Three RNAs play the key roles!!

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RNA TRANSLATION
Protein Synthesis the formation of a protein
using information coded on DNA and carried out by
RNA in the assembly of amino acids.

• Proteins are
• Amino acids in chains 20 kinds
• Made of 10s or 100s or 1000s of amino acids
• Must be arranged in a specific sequence for each
  type of protein
• Function type of protein is determined by amino
  acid sequence
• DNA makes RNA
• RNA constructs amino acids

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mRNA - Codons

• Read 3 bases at a time on the mRNA called
  CODONS!!!!
• Each combination of 3 nucleotides on mRNA is
  called a codon or three-letter code word.
• Each codon specifies a particular amino acid that
  is to be placed in the polypeptide chain
  (protein).

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Protein Synthesis Translation
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A Codon
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Start codons and Stop codons

• For translation to begin, there is a START codon.
• AUG is the 3 letter codon that starts the
  process.
• UAA, UGA, UAG Stop codons.

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Start Codon

• Start codon codon AUG also serves as the
  initiator codon, which starts the synthesis of
  a protein.

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Stop Codon

• STOP codon Codon that signal the end of the
  protein. (UAA, UAG, UGA
• Besides selecting the amino acid methionine, the
  codon AUG also serves as the initiator codon,
  which starts the synthesis of a protein

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Protein Synthesis Translation

• A three-letter code is used because there are 20
  different amino acids that are used to make
  proteins.
• If a two-letter code were used there would not be
  enough codons to select all 20 amino acids.
• That is, there are 4 bases in RNA, so 42 (4x
  4)16 where as 43 (4x4x4)64.

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Translation

• Therefore, there is a total of 64 codons with
  mRNA, 61specify a particular amino acid.
• This means there are more than one codon for
  each of the 20 amino acids.

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Protein Synthesis Translation
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Protein Synthesis Translation

• Transfer RNA (tRNA)
• Each tRNA molecule has 2 important sites of
  attachment.
• One site, called the anticodon, binds to the
  codon on the mRNA molecule.
• The other site attaches to a particular amino
  acid.
• During protein synthesis, the anticodon of a tRNA
  molecule base pairs with the appropriate mRNA
  codon.

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tRNA

• Transfer RNA
• Bound to one amino acid on one end
• Anticodon on the other end complements mRNA codon
• If they do not match then the tRNA is rejected!!!!

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Met-tRNA
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tRNA parts
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Parts of a Ribosomes - rRNA

• Ribosomes are composed of 2 subunits separate in
  cytoplasm
• Large
• Small
• Contain 3 binding sites helps tRNA align
• to codon.
• E
• P
• A

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Steps of Translation

• 1. INITIATION
• A.The initiator(start) codon AUG binds to the
  first anticodon of tRNA, signaling the start of a
  protein.
• B. Two parts of the ribosome join around the
  tRNA and mRNA.
• The amino acid methionine, the codon AUG also
  serves as the initiator codon, which starts the
  synthesis of a protein at site P.

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Translation

• 2. ELONGATION The anticodon of another tRNA
  binds to the next mRNA codon at site A, bringing
  the 2nd amino acid to be placed in the protein.
  This will continue until stop codon.
• As each anticodon codon bind together a peptide
  bond forms between the two amino acids.

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Protein Synthesis Translation

• 3. Termination The protein chain continues to
  grow until a stop codon reaches the ribosome,
  which results in the release of the new protein
  and mRNA, completing the process of translation.
  The amino acids are bonded with a peptide bond to
  form a protein.
• Release factor causes the release of tRNA and
  mRNA.

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http//staff.jccc.net/pdecell/proteinsynthesis/tra
nslation/steps.html
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Summary of Translation

• Ribosome 2 parts come together.
• mRNA attaches to ribosome.
• AUG start codon.
• tRNA brings in making anticodon with amino acid.
• rRNA continues to read mRNA and bring in
• making tRNA.
• Stop codon will stop process. Peptide bonds
  will form to make a protein.

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Translation - Initiation
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Translation - Elongation
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Translation - Elongation
Aminoacyl tRNA
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Translation - Elongation
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Translation - Elongation
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The Genetic Code
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Protein Synthesis
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Transcription And Translation In Prokaryotes ALL
IN CYTOPLASM!!!
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Transcription vs. Translation Review

• Transcription
• Process by which genetic information encoded in
  DNA is copied onto messenger RNA
• Occurs in the nucleus
• DNA mRNA

• Translation
• Process by which information encoded in mRNA is
  used to assemble a protein at a ribosome
• Occurs on a Ribosome
• mRNA protein

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Pigment is produced in the petal cells of the
plant as the result of a chemical reaction. A
chemical reaction takes place in the cytoplasm of
a cell in which a colorless molecule is changed
to a different molecule that now absorbs light
and reflects red light without assistance. This
reaction would take place very slowly and not
much pigment would be produced during the life of
the plant. As with almost all chemical reactions
inside cells, this reaction is catalyzed by an
enzyme which speeds up the rate of the reaction
hundreds of thousands of times. In the presence
of the enzyme, enough pigment is produced to
quickly turn the cells and petals of the flower
red. Without the enzyme, the cells would
essentially stay colorless. With the enzyme, the
plant flowers can turn red. The red flower trait
is thus the result of the activity of an enzyme.
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http//www.bioinformatics.org/tutorial/1-1.html
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How Is DNA Responsible for What you Look Like or
How You Feel? The DNA in each chromosome makes up
many genes (as well as vast stretches of
noncoding DNA(introns), the function of which is
unknown). A gene is any given segment along the
DNA that encodes instructions that allow a cell
to produce a specific product - typically, a
protein such as an enzyme - that initiates one
specific action. There are between 50,000 and
100,000 genes. These PROTEINS determine
everything about you. SO your DNA control this
code and what you look like!!!! It determines
the amino acid codes!!
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MUTATIONS

• Changes in DNA that affect genetic information

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Gene Mutations

• Point Mutations changes in one or a few
  nucleotides
• Substitution
• THE FAT CAT ATE THE RAT
• THE FAT HAT ATE THE RAT
• Insertion
• THE FAT CAT ATE THE RAT
• THE FAT CAT XLW ATE THE RAT
• Deletion
• THE FAT CAT ATE THE RAT
• THE FAT ATE THE RAT

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Gene Mutations

• Frameshift Mutations shifts the reading frame
  of the genetic message so that the protein may
  not be able to perform its function.
• Insertion
• THE FAT CAT ATE THE RAT
• THE FAT HCA TAT ETH ERA T
• Deletion
• THE FAT CAT ATE THE RAT
• TEF ATC ATA TET GER AT

H
H
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Sex Chromosome Abnormalities

• XYY Syndrome
• Normal male traits
• Often tall and thin
• Associated with antisocial and behavioral problems

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Chromosome Mutations

• Changes in number and structure of entire
  chromosomes
• Original Chromosome ABC DEF
• Deletion AC DEF
• Duplication ABBC DEF
• Inversion AED CBF
• Translocation ABC JKL
• GHI DEF

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Significance of Mutations

• Most are neutral
• Eye color
• Birth marks
• Some are harmful
• Sickle Cell Anemia
• Down Syndrome
• Some are beneficial
• Sickle Cell Anemia to Malaria
• Immunity to HIV

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What Causes Mutations?

• There are two ways in which DNA can become
  mutated
• Mutations can be inherited.
• Parent to child
• Mutations can be acquired.
• Environmental damage
• Mistakes when DNA is copied

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Chromosome Mutations

• Down Syndrome
• Chromosome 21 does not separate correctly.
• They have 47 chromosomes in stead of 46.
• Children with Down Syndrome develop slower, may
  have heart and stomach illnesses and vary greatly
  in their degree of inteligence.

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Chromosome Mutations

• Cri-du-chat
• Deletion of material on 5th chromosome
• Characterized by the cat-like cry made by
  cri-du-chat babies
• Varied levels of metal handicaps

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Sex Chromosome Abnormalities

• Klinefelters Syndrome
• XXY, XXYY, XXXY
• Male
• Sterility
• Small testicles
• Breast enlargement

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Sex Chromosome Abnormalities

• XYY Syndrome
• Normal male traits
• Often tall and thin
• Associated with antisocial and behavioral problems

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Sex Chromosome Mutations

• Turners Syndrome
• X
• Female
• sex organs don't mature at adolescence
• sterility
• short stature

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Sex Chromosome Mutations

• XXX
• Trisomy X
• Female
• Little or no visible differences
• tall stature
• learning disabilities
• limited fertility

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