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DNA Module B: Bio. B.1

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Describe the sculpture

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Bio. B.1.2: Explain how genetic information is inherited Bio.B.1.2.1-Describe how the process of DNA replication results in the transmission and/or conservation of genetic material.

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Before we get started What is genetics? What is the genetic material?

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The Role of DNA: What is the role of DNA in heredity? DNA must be capable of: 1. Storing information 2. Copying information 3. Transmitting information

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DNA stores information

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DNA copies and transmits information

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DNA is made of nucleotides Nucleotides are the building blocks of DNA Nucleotides composed of: 1. Phosphate 2. Sugar (deoxyribose) 3. Nitrogen Base Adenine (A) Guanine (G) Cytosine (C) Thymine (T)

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Nucleotides link together

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STRUCTURE of DNA Chargaff: Chargaffs Rule: percentages of A (adenine) and T(thymine) were equal in many sample of DNA percentages of C (Cytosine) and G (Guanine) were also equal

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STRUCTURE of DNA Chargaffs Data If a species has 35% adenine in its DNA, what is the percentage of the other three bases? Can you figure it out?

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STRUCTURE of DNA Rosalind Franklin X-ray picture of DNA DNA had two strands that twisted around each other like a coil

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STRUCTURE of DNA Watson and Crick James Watson and Francis Crick built a three dimensional model of DNA Shape of the DNA = double helix. Strands run in opposite direction (anti-parallel) Base pairing rules (A pairs with T; C pairs with G) Strands held together by hydrogen bonds Watson TED talk

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Antiparallel DNA Strands:

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What happens to the DNA structure during S phase? DNA replicates (duplicates, is copied, etc.) Watson and Cricks 3D model immediately proposed a replication mechanism animation

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DNA Replication: DNA gets copied during interphase Ensures that each resulting cell has the same complete set of DNA Each strand has all the information needed to construct the other strand

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Process of DNA Replication: 1. DNA is unzipped or separated Enzyme = helicase Breaks hydrogen bonds that hold the two strands of DNA together

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2.New strands are built Enzyme = DNA polymerase Joins individual nucleotides together to produce a new strand of DNA that is complementary to the other Proofreads each new strand Process of DNA Replication:

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How is replication different in prokaryotes? In eukaryotes, replication begins at many different locations and proceeds in both directions until each chromosome is completely copied In prokaryotes, replication begins at one point and proceeds in two directions until the entire chromosome Is copied

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DNA Replication Prokaryotes Vs eukaryotes

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Quick Check 1. A nucleotide does not contain A.A 5-carbon sugar B.An amino acid C.A nitrogen base D.A phosphate group

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Quick Check 2. According to Chargaffs rule of base pairing which of the following is true about DNA? A.A=T and C=G B.A=C and T=G C.A=G and T=C D.A=T=G=C

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Quick Check 3. The bonds that hold the two strands of DNA together come from A.The attraction of phosphate groups for each other B.Strong bonds between nitrogenous bases and the sugar-phosphate backbone C.Weak hydrogen bonds between bases D.Carbon-to-carbon bonds in the sugar portion of the nucleotides

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Quick Check 4. In prokaryotes, DNA molecules are located in the A.Nucleus B.Ribosomes C.Cytoplasm D.histones

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Quick Check 5. In eukaryotes, nearly all the DNA is found in the A.Nucleus B.Ribosomes C.Cytoplasm D.histones

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Quick Check 6. The main enzyme involved in linking individual nucleotides into DNA molecules is A.DNA protease B.Ribose C.Carbohydrate D.DNA polymerase

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PREC-CLASS All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell?

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Central Dogma of Molecular Biology Describes flow of information from DNA to protein RNADNAProtein transcriptiontranslation RNA is the link between DNA and proteins.

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Analogy for central dogma The master plan has all the information needed to construct a building.

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Analogy for central dogma But builders never bring a valuable master plan to the building site where is might be damaged or lost.

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Analogy for central dogma Instead, builders work from blueprints, inexpensive disposable copies of the master plan.

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Analogy for central dogma Master plan = DNA Building site = ribosomes (in cytoplasm) Blueprint copies = RNA

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DNA vs RNA DNA Double stranded Made of nucleotides Sugar = deoxyribose Bases = C,G, A, T RNA Single stranded Made of nucleotides Sugar = ribose Bases = U instead of T

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Different types of RNA 1.Messenger RNA carries the instructions from DNA to cytoplasm on how to make the protein 2.Ribosomal RNA form ribosomes in cytoplasm to help build the protein 3.Transfer RNA delivers the amino acids needed to build the protein

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Transcription (RNA synthesis) DNA RNA Occurs in the nucleus Requires RNA polymerase Builds RNA strand Uses one strand of DNA as template Involves single gene Produces MANY RNA copies

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RNAi Video RNAi Video

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Replication vs Transcription Replication copies the entire DNA Transcription only copies one gene Replication only makes one copy Transcription makes many copies BOTH involve complex enzymes BOTH follow complementary base pairing BOTH occur in the nucleus

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If you were given the sequence of a DNA strand, could you figure out the sequence of the mRNA strand? Remember, U instead of T in RNA!!! For example: DNA T A C G C C C T A T T G A T mRNA ?? A U G C G G G A UA AC U A

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Central Dogma of Molecular Biology Describes flow of information from DNA to protein RNADNAProtein transcriptiontranslation

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Translation (protein synthesis) RNA protein Occurs in the cytoplasm Involves ribosome, mRNA, tRNA and amino acids RNA is translated into amino acid sequence

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The language of protein synthesis Language of RNA = nucleotides Language of protein = amino acids Triplet code: three mRNA bases (codon) code for one amino acid

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Genetic Code: Codon = a group of three nucleotide bases in the mRNA that codes for a particular amino acid

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Genetic Code: (mRNA codon to amino acid)

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Genetic Code START codon signals the start of translation AUG also codes for methionine STOP codons signal stop of translation UGA, UAA, UAG Do not code for any amino acid

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Genetic Code = common language UNIVERSAL shared by all organisms REDUNDANT more than one codon may code for the same amino acid Allows flexibility if mistakes are made

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Quick Check A certain gene has the following base sequence: GACAAGTCCAATC Write the sequence of the mRNA molecule transcribed from this gene Divide you mRNA sequence into codons How many codons? What amino acid does each codon code for? How many amino acids?

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QUICK CHECK Remember, U instead of T in RNA!!! For example: DNA T A C G C C C T A T T G A T A mRNA ?? Amino acids

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The role of ribosomes in translation Ribosomes act as the machinery Ribosomes use the sequence of codons in mRNA to assemble amino acids into protein chains

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Each tRNA molecule carries one kind of amino acid Anticodon on tRNA recognizes complementary codon on mRNA For example, tRNA for methionine has the anticodon UAC which pairs with the methionine codon (AUG) The role of tRNA in translation

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Process of Translation 1.Ribosome binds to mRNA 2.mRNA codons attract complementary tRNA anticodons 3.peptide bond forms between amino acids then breaks bond holding the amino acid to the tRNA 4.Empty tRNA leaves; the ribosome pulls the mRNA exposing the next codon

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QUICK CHECK Remember, U instead of T in RNA!!! For example: DNA T A C G C C C T A T T G A T A mRNA ?? Amino acids tRNA

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Central Dogma of Molecular Biology Describes flow of information from DNA to protein RNADNAProtein transcriptiontranslation

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Mutations are changes in the DNA 1.Gene mutations (single gene) 2.Chromosomal mutations (multiple genes involved) mutated base

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1. Gene Mutations Also known as point mutations because they occur at a single point in the DNA sequence Occur during replication Different types A.Substitutions B.Insertions and deletions

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A. Substitutions One base is changed to a different base Only affect one amino acid Sometimes have no effect (silent) EX: changing mRNA codon from CCC to CCA Codon still specifies proline; SILENT EX: changing mRNA codon from CCC to ACC Replaces proline with threonine

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B. Insertions and Deletions Frameshift mutations shift the reading frame Effects are dramatic Can change every amino acid after the mutation

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Frameshift Mutations

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2. Chromosome mutations Changes in number or structure of chromosomes Occur during meiosis Four types A.Deletion (loss of all or part of a chromosome) B.Duplication (extra copy) C.Inversion (reverse in the direction of a chromosome) D.Translocation (one chromosome attaches to another)

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Mutagens Chemical or physical agents in the environment that can cause mutations in DNA Include Pesticides, tobacco, environmental pollutants, UV light, X-rays

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Harmful and Helpful Mutations Mutations can be harmful if They cause drastic changes in the protein that is produced Defective proteins can disrupt normal function Ex: sickle cell anemia, some cancer

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Harmful and Helpful Mutations Beneficial effects Variation produced by mutations can be highly advantageous to organisms in different or changing environments Responsible for evolution EX: pesticide resistance (bad news for humans but good news for mosquitoes) EX: human resistance to HIV