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DNA
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Nucleic Acids DNA and RNA are examples Deoxyribonucleic acid
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Nucleic Acids A gene is a section of DNA that provides the code to make a protein.
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Nucleic Acids Built from monomers of nucleotides
Consists of a phosphate group, a sugar molecule, and a nitrogenous base
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Nitrogenous bases Purines – double ring -adenine, guanine
A=T C=G Purines – double ring -adenine, guanine Pyrimidines – single ring thymine, cytosine
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Tight helical fiber (30-nm diameter)
Huge molecule over 3 billion base pairs per cell Condenses by wrapping/coiling around histones -called a chromosome Linker DNA double helix (2-nm diameter) “Beads on a string” Tight helical fiber (30-nm diameter) Metaphase chromosome Histones Nucleosome (10-nm diameter) Supercoil (300-nm diameter) 700 nm Figure 11.2a-0 DNA packing in a eukaryotic chromosome
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How did we discover DNA is the genetic material?
In a group or individually, read through page 182 and figure 10.1B (183) What did Fredrick Griffith discover? What did Alfred Hershey and Martha Chase discover? What was their experiment?
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Hershey Chase Animation
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Batch 1: Radioactive protein labeled in yellow
Phage Bacterium Radioactive protein DNA Empty protein shell Phage DNA Centrifuge Pellet Batch 1: Radioactive protein labeled in yellow Radioactive DNA The radioactivity is in the pellet. The radioactivity is in the liquid. Batch 2: Radioactive DNA labeled in green Figure 10.1b-0 The Hershey-Chase experiment
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How was the double helix discovered?
Read pages 186 and 187
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Thymine (T) Cytosine (C) Adenine (A) Guanine (G) Pyrimidines Purines
Figure 10.2b-0 The nitrogenous bases of DNA
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Recall: The experiment from Hershey and Chase (1952) demonstrated DNA is the passed from parents to offspring, but what is its structure? Phage Bacterium Radioactive protein DNA Empty protein shell Phage DNA Centrifuge Pellet Batch 1: Radioactive protein labeled in yellow Radioactive DNA The radioactivity is in the pellet. The radioactivity is in the liquid. Batch 2: Radioactive DNA labeled in green Figure 10.1b-0 The Hershey-Chase experiment
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Discovering the Structure of DNA
Watson and Crick were the first to discover the structure of DNA. Used data x-ray crystallography data from Wilkins and Franklin without their permission
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Earliest Model of DNA
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Make our own models Two simple steps Label the nitrogenous bases
Fold it
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DNA We know the structure of DNA, and that more than 3 billion base pairs are in each cell, what about new cells?
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DNA Replication Depends on specific base pairs adenine – thymine
guanine – cytosine If this is one half of DNA, what would the other half be?
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DNA Replication Semiconservative model
The two DNA strands separate (parent strands). Each parent strand then becomes a template for a new, complementary strand (daughter strand) forming two new daughter molecules of DNA Each new DNA helix has one old strand with one new strand.
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Daughter DNA molecules
Figure 10.4b A T G C A T Parental DNA molecule A T T A C G G C T Daughter strand Parental strand A C C G G G C T G C T T C A A G Figure 10.4b The untwisting and replication of DNA A G T A C C A G T A T A T A G Daughter DNA molecules T C
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DNA Replication Over a dozen enzymes and other proteins needed to replicate DNA DNA polymerase – adds nucleotides one at a time to the strand Other enzymes “proofread” and fix mistakes
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DNA Replication Replication occurs at multiple points at the same time
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DNA Replication Carbons are labeled The direction DNA polymerase moves is determined by the sugar phosphate backbone There is a 5’ end and a 3’ end Nucleotides are added onto the 3’ end, moving towards the 5’ end
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DNA polymerase molecule 3′
This daughter strand is synthesized continuously 5′ Parental DNA 5′ 3′ Replication fork This daughter strand is synthesized in pieces 3′ 5′ 5′ Figure 10.5c How daughter DNA strands are synthesized 3′ DNA ligase Overall direction of replication
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Recall A gene is a section of DNA that provides the code to make a protein. Genes carry different information on them Human Genome mapped it out – ethical questions
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https://www. youtube. com/watch
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Parent molecule Daughter molecules
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Parent strand Daughter strand
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Daughter DNA molecules
Parental DNA molecule A T T A C G G Daughter strand C T Parental strand A C C G G G C T G C T C A A T G Figure 10.4b The untwisting and replication of DNA A G T A C C A G T A T A T A G Daughter DNA molecules T C
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Hypothetical DNA If this is the parent strand? What is the daughter strand? A - T - C - G -
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What was the main enzyme in DNA replication
What was the main enzyme in DNA replication? What was unique as a result of the sugar phosphate backbone?
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DNA polymerase molecule 3′
This daughter strand is synthesized continuously 5′ Parental DNA 5′ 3′ Replication fork This daughter strand is synthesized in pieces 3′ 5′ 5′ Figure 10.5c How daughter DNA strands are synthesized 3′ DNA ligase Overall direction of replication
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3’ 5’
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After DNA replicates, the cell divides
Looking at that after break. Why is DNA Critical?
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Transcription and Translation
DNA is transcribed into RNA RNA is translated into protein DNA NUCLEUS CYTOPLASM RNA Transcription Translation Protein
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DNA Ingredientes: 2 1 / 4 tazas de harina para todo uso
1 cucharadita de bicarbonato de soda 1 cucharadita de sal 1 taza (2 palos) de mantequilla, suavizada 3 / 4 taza de azúcar granulada 3 / 4 taza de azúcar morena 1 cucharadita de extracto de vainilla 2 huevos grandes 2 tazas (12 oz. Pkg.) TELEPEAJE CASA NESTLÉ ® ® semi-dulce de chocolate bocados 1 taza de nueces picadas
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RNA Ingredients: To 2 1/4 cups all-purpose flour
1 teaspoon baking soda 1 teaspoon salt 1 cup (2 sticks) butter, softened 3/4 cup granulated sugar 3/4 cup brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12 oz. Pkg.) NESTLÉ TOLL HOUSE ® ® semi-sweet chocolate morsels 1 cup chopped walnuts
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Protein
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Transcription Sections of DNA called genes are used
RNA polymerase attaches to the DNA at a ‘promoter’ site It moves along the gene forming a new RNA strand using the base pair rules
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Transcription DNA Base pairs
A-T G-C There is no thymine in RNA, a different nucleotide Uracil is used RNA Base pairs A-U G-C
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DNA Transcription RNA Codon Translation Polypeptide Amino acid
A A A C C G G C A A A A Transcription RNA U U U G G C C G U U U U Codon Translation Figure Transcription and translation of codons (partial) Polypeptide Amino acid
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Quick review
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DNA replication Lots of enzymes, DNA polymerase one of them
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DNA codes for protein Only part of DNA is a gene
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Transcription and Translation
DNA is transcribed into RNA RNA is translated into protein DNA NUCLEUS CYTOPLASM RNA Transcription Translation Protein
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DNA Ingredientes: 2 1 / 4 tazas de harina para todo uso
1 cucharadita de bicarbonato de soda 1 cucharadita de sal 1 taza (2 palos) de mantequilla, suavizada 3 / 4 taza de azúcar granulada 3 / 4 taza de azúcar morena 1 cucharadita de extracto de vainilla 2 huevos grandes 2 tazas (12 oz. Pkg.) TELEPEAJE CASA NESTLÉ ® ® semi-dulce de chocolate bocados 1 taza de nueces picadas
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RNA Ingredients: To 2 1/4 cups all-purpose flour
1 teaspoon baking soda 1 teaspoon salt 1 cup (2 sticks) butter, softened 3/4 cup granulated sugar 3/4 cup brown sugar 1 teaspoon vanilla extract 2 large eggs 2 cups (12 oz. Pkg.) NESTLÉ TOLL HOUSE ® ® semi-sweet chocolate morsels 1 cup chopped walnuts
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Protein
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Transcription Sections of DNA called genes are used
RNA polymerase attaches to the DNA at a ‘promoter’ site It moves along the gene forming a new RNA strand using the base pair rules
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Transcription DNA Base pairs
A-T G-C There is no thymine in RNA, a different nucleotide Uracil is used RNA Base pairs A-U G-C
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Figure 10.7-1 Transcription and translation of codons (partial)
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Transcription RNA polymerase recognizes part of the DNA strand and attaches at the promoter region
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Transcription RNA synthesis begins after attachment
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Transcription Using DNA as a template, RNA polymerase adds RNA nucleotides one at a time
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Transcription Using DNA as a template, RNA polymerase adds RNA nucleotides one at a time If the DNA strand is: ATAGGC Then the RNA will be: UAUCCG U U A C G C A U A G C G DNA - A A T G C G T A T C G C
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Transcription RNA synthesis ends when RNA polymerase reaches the terminator DNA sequence
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Initiation Elongation Termination Direction of transcription
RNA synthesis begins after RNA polymerase attaches to the promoter. Unused strand of DNA RNA polymerase Terminator DNA DNA of gene Newly formed RNA Template strand of DNA Promoter Elongation Direction of transcription Using the DNA as a template, RNA polymerase adds free RNA nucleotides one at a time. Free RNA nucleotide DNA strands reunite U A T C C A A T C G T A U G A U C C A A A T A G G T T A DNA strands separate Figure Transcription of a gene (step 3) Newly made RNA Termination RNA synthesis ends when RNA polymerase reaches the terminator DNA sequence. Terminator DNA Completed RNA RNA polymerase detaches
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Transcription and Translation
DNA is transcribed into RNA RNA is translated into protein DNA NUCLEUS CYTOPLASM RNA Transcription Translation Protein Before leaving the nucleus, the RNA is processed
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Transcription Addition of cap and tail
Exon DNA Intron Transcription Addition of cap and tail Tail Introns removed Exons spliced together Cap Coding sequence RNA transcript with cap and tail mRNA Figure The production of eukaryotic mRNA NUCLEUS CYTOPLASM
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RNA processing A ‘cap’ and ‘tail’ are added – helps protect the RNA
Introns (intervening sequences) are removed Exons (expressed sequences) are spliced together Exon DNA Intron
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Transcription and Translation
DNA is transcribed into RNA RNA is translated into protein DNA NUCLEUS CYTOPLASM RNA Transcription Translation Protein
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Translation The genetic code is the amino acid translations of each of the nucleotide triplets. Three nucleotides specify one amino acid
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Translation Sixty-one codons correspond to amino acids
64 Total Sixty-one codons correspond to amino acids AUG codes for methionine and signals the start of translation Three “stop” codons signal the end of translation
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Strand to be transcribed
T A C T T C A A A A T C DNA A T G A A G T T T T A G Figure 10.8b-1 Deciphering the genetic information in DNA (step 1)
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Strand to be transcribed
T A C T T C A A A A T C DNA A T G A A G T T T T A G Transcription RNA A U G A A G U U U U A G Figure 10.8b-2 Deciphering the genetic information in DNA (step 2)
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Strand to be transcribed
T A C T T C A A A A T C DNA A T G A A G T T T T A G Transcription RNA A U G A A G U U U U A G Figure 10.8b-3 Deciphering the genetic information in DNA (step 3) Start codon Stop codon Translation Polypeptide Met Lys Phe
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Translation Types of RNA
Messenger RNA – RNA that will be coded into protein (mRNA) Transfer RNA – RNA that is used in the decoding process (tRNA) Ribosomal RNA – part of the ribosome that puts the protein together (adds amino acids together) (rRNA)
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Translation tRNA There are 61, for each of the codons
Contains a section called the anticodon that base pairs with the codon on mRNA
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Translation Ribosome A complex of rRNA and protein
A small subunit and a large subunit Contains two sites for tRNA – A site and P site
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Translation How does it actually work?
Recall, mRNA was just transcribed in the nucleus and then processed before entering the cytoplasm DNA NUCLEUS CYTOPLASM RNA Transcription Translation Protein
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Translation mRNA binds to a the small subunit of a ribosome
a tRNA recognizes the start codon and binds
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Translation The large ribosomal subunit binds to the small subunit
The tRNA fits into the P site
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Translation A new tRNA carrying an amino acid moves into the A site, amino acids are combined The tRNAs shift over This repeats until stop codon is reached
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Amino acid Polypeptide Anticodon P site A site mRNA Codons
1 Codon recognition Figure Polypeptide elongation (step 1)
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Peptide bond formation
Amino acid Polypeptide Anticodon P site A site mRNA Codons 1 Codon recognition Figure Polypeptide elongation (step 2) 2 Peptide bond formation
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Peptide bond formation
Amino acid Polypeptide Anticodon P site A site mRNA Codons 1 Codon recognition Figure Polypeptide elongation (step 3) New peptide bond 2 Peptide bond formation 3 Translocation
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Peptide bond formation
Amino acid Polypeptide Anticodon P site A site mRNA Codons 1 Codon recognition mRNA movement Stop codon Figure Polypeptide elongation (step 4) New peptide bond 2 Peptide bond formation 3 Translocation
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Try it DNA: T A C A A T C G T A C G (one strand) RNA: Amino Acid:
A U G U U A G C A U G C Met – Leu – Ala – Cys
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