Figure 10.9B_3

Figure 10.9B_3

Figure 10.9B_3 3 Completed RNA Termination Growing RNA RNA polymerase 10.10 Eukaryotic RNA is processed before leaving the nucleus as mRNA Messenger RNA (mRNA) encodes amino acid sequences and conveys genetic messages from DNA to the translation

machinery of the cell, which in prokaryotes, occurs in the same place that mRNA is made, but in eukaryotes, mRNA must exit the nucleus via nuclear pores to enter the cytoplasm. Eukaryotic mRNA has introns, interrupting sequences that separate exons, the coding regions. 2012 Pearson Education, Inc. 10.10 Eukaryotic RNA is processed before leaving the nucleus as mRNA Eukaryotic mRNA undergoes processing before leaving the nucleus. RNA splicing removes introns and joins exons to produce a continuous coding sequence. A cap and tail of extra nucleotides are added to the ends of the mRNA to

facilitate the export of the mRNA from the nucleus, protect the mRNA from attack by cellular enzymes, and help ribosomes bind to the mRNA. 2012 Pearson Education, Inc. Figure 10.10 Exon Intron Exon Intron Exon DNA Cap RNA transcript

with cap and tail Transcription Addition of cap and tail Introns removed Tail Exons spliced together mRNA Coding sequence NUCLEUS CYTOPLASM 10.11 Transfer RNA molecules serve as interpreters during translation Transfer RNA (tRNA) molecules function as a language interpreter,

converting the genetic message of mRNA into the language of proteins. Transfer RNA molecules perform this interpreter task by picking up the appropriate amino acid and using a special triplet of bases, called an anticodon, to recognize the appropriate codons in the mRNA. 2012 Pearson Education, Inc. Figure 10.11A Amino acid attachment site Hydrogen bond RNA polynucleotide chain

Anticodon A tRNA molecule, showing its polynucleotide strand and hydrogen bonding A simplified schematic of a tRNA Figure 10.11B Enzyme tRNA ATP 10.12 Ribosomes build polypeptides Translation occurs on the surface of the ribosome. Ribosomes coordinate the functioning of mRNA and tRNA and, ultimately, the synthesis of polypeptides.

Ribosomes have two subunits: small and large. Each subunit is composed of ribosomal RNAs and proteins. Ribosomal subunits come together during translation. Ribosomes have binding sites for mRNA and tRNAs. 2012 Pearson Education, Inc. Figure 10.12A Growing polypeptide tRNA molecules Large subunit Small subunit mRNA

Figure 10.12B tRNA binding sites Large subunit P A site site Small subunit mRNA binding site Figure 10.12C The next amino acid to be added to the polypeptide

Growing polypeptide mRNA tRNA Codons 10.13 An initiation codon marks the start of an mRNA message Translation can be divided into the same three phases as transcription: 1. initiation, 2. elongation, and 3. termination. Initiation brings together mRNA, a tRNA bearing the first amino acid, and

the two subunits of a ribosome. 2012 Pearson Education, Inc. 10.13 An initiation codon marks the start of an mRNA message Initiation establishes where translation will begin. Initiation occurs in two steps. 1. An mRNA molecule binds to a small ribosomal subunit and the first tRNA binds to mRNA at the start codon. The start codon reads AUG and codes for methionine. The first tRNA has the anticodon UAC. 2. A large ribosomal subunit joins the small subunit, allowing the ribosome to function. The first tRNA occupies the P site, which will hold the growing peptide chain. The A site is available to receive the next tRNA. 2012 Pearson Education, Inc.

Figure 10.13A Start of genetic message Cap End Tail Figure 10.13B Met Met Large ribosomal subunit Initiator

tRNA P site mRNA U A C A U G Start codon 1 Small ribosomal subunit 2 U A C A U G

A site 10.14 Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation Once initiation is complete, amino acids are added one by one to the first amino acid. Elongation is the addition of amino acids to the polypeptide chain. 2012 Pearson Education, Inc. 10.14 Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation Each cycle of elongation has three steps. 1. Codon recognition: The anticodon of an incoming tRNA molecule, carrying its amino acid, pairs with the mRNA codon in the A site of the ribosome.

2. Peptide bond formation: The new amino acid is joined to the chain. 3. Translocation: tRNA is released from the P site and the ribosome moves tRNA from the A site into the P site. 2012 Pearson Education, Inc. 10.14 Elongation adds amino acids to the polypeptide chain until a stop codon terminates translation Elongation continues until the termination stage of translation, when the ribosome reaches a stop codon, the completed polypeptide is freed from the last tRNA, and the ribosome splits back into its separate subunits. Animation: Translation 2012 Pearson Education, Inc.

Figure 10.14_s1 Polypeptide P site mRNA Amino acid A site Anticodon Codons 1

Codon recognition Figure 10.14_s2 Polypeptide P site mRNA Amino acid A site Anticodon Codons 1

Codon recognition 2 Peptide bond formation Figure 10.14_s3 Polypeptide P site mRNA Amino acid A

site Anticodon Codons 1 Codon recognition 2 New peptide bond 3 Translocation Peptide bond

formation Figure 10.14_s4 Polypeptide P site mRNA Amino acid A site Anticodon Codons 1

Codon recognition mRNA movement Stop codon 2 New peptide bond 3 Translocation Peptide bond formation

10.15 Review: The flow of genetic information in the cell is DNA RNA protein Transcription is the synthesis of RNA from a DNA template. In eukaryotic cells, transcription occurs in the nucleus and the mRNA must travel from the nucleus to the cytoplasm. 2012 Pearson Education, Inc. 10.15 Review: The flow of genetic information in the cell is DNA RNA protein Translation can be divided into four steps, all of which occur in the cytoplasm: 1. amino acid attachment, 2. initiation of polypeptide synthesis, 3. elongation, and 4. termination. 2012 Pearson Education, Inc.

Figure 10.15 Transcription DNA 1 mRNA Transcription RNA polymerase CYTOPLASM Translation Amino acid Amino acid

attachment 2 Enzyme tRNA ATP Anticodon Initiator tRNA Large ribosomal subunit Start Codon mRNA Initiation of

polypeptide synthesis 3 Small ribosomal subunit New peptide bond forming Growing polypeptide 4 Elongation Codons mRNA Polypeptide

5 Stop codon Termination Figure 10.15_1 DNA mRNA Transcription 1 RNA polymerase Transcription

Figure 10.15_2 CYTOPLASM Translation Amino acid Amino acid attachment 2 Enzyme tRNA ATP Anticodon Initiator

tRNA Large ribosomal subunit Start Codon mRNA Small ribosomal subunit Initiation of polypeptide synthesis 2 3 Figure 10.15_3

New peptide bond forming Growing polypeptide 4 Elongation Codons mRNA Polypeptide 5 Stop codon Termination

10.16 Mutations can change the meaning of genes A mutation is any change in the nucleotide sequence of DNA. Mutations can involve large chromosomal regions or just a single nucleotide pair. 2012 Pearson Education, Inc. 10.16 Mutations can change the meaning of genes Mutations within a gene can be divided into two general categories. 1. Base substitutions involve the replacement of one nucleotide with another. Base substitutions may have no effect at all, producing a silent mutation, change the amino acid coding, producing a missense mutation, which produces a different amino acid, lead to a base substitution that produces an improved protein that enhances the success of the mutant organism and its descendant, or

change an amino acid into a stop codon, producing a nonsense mutation. 2012 Pearson Education, Inc. 10.16 Mutations can change the meaning of genes 2. Mutations can result in deletions or insertions that may alter the reading frame (triplet grouping) of the mRNA, so that nucleotides are grouped into different codons, lead to significant changes in amino acid sequence downstream of the mutation, and produce a nonfunctional polypeptide. 2012 Pearson Education, Inc. 10.16 Mutations can change the meaning of genes Mutagenesis is the production of mutations. Mutations can be caused by spontaneous errors that occur during DNA replication or recombination or mutagens, which include

high-energy radiation such as X-rays and ultraviolet light and chemicals. 2012 Pearson Education, Inc. Figure 10.16A Normal hemoglobin DNA C T Mutant hemoglobin DNA C A T T mRNA mRNA G A A

G U A Normal hemoglobin Sickle-cell hemoglobin Val Glu Figure 10.16B Normal gene mRNA Protein Nucleotide substitution

A U G A Met A U G A Met A G U Lys U U G G C G C

Phe Gly Ala U A G C A G U U Lys Phe Ser G C A

A Ala U Deleted Nucleotide deletion A U G A Met A G U U G G C G Ala

Leu Lys C A U His Inserted Nucleotide insertion A U G A Met A G

Lys U U G Leu U G G C G C Ala His THE GENETICS OF VIRUSES AND BACTERIA

2012 Pearson Education, Inc. 10.17 Viral DNA may become part of the host chromosome A virus is essentially genes in a box, an infectious particle consisting of a bit of nucleic acid, wrapped in a protein coat called a capsid, and in some cases, a membrane envelope. Viruses have two types of reproductive cycles. 1. In the lytic cycle, viral particles are produced using host cell components, the host cell lyses, and viruses are released. 2012 Pearson Education, Inc. 10.17 Viral DNA may become part of the host chromosome 2. In the Lysogenic cycle

Viral DNA is inserted into the host chromosome by recombination. Viral DNA is duplicated along with the host chromosome during each cell division. The inserted phage DNA is called a prophage. Most prophage genes are inactive. Environmental signals can cause a switch to the lytic cycle, causing the viral DNA to be excised from the bacterial chromosome and leading to the death of the host cell. Animation: Phage Lambda Lysogenic and Lytic Cycles Animation: Phage T4 Lytic Cycle 2012 Pearson Education, Inc. Figure 10.17_s1 Phage Attaches to cell Phage DNA 4

The cell lyses, releasing phages 1 Bacterial chromosome The phage injects its DNA Lytic cycle Phages assemble 3 2 New phage DNA and

proteins are synthesized The phage DNA circularizes Figure 10.17_s2 Phage Attaches to cell Phage DNA 4 The cell lyses, releasing phages 1 Bacterial

chromosome The phage injects its DNA 7 Lytic cycle Phages assemble Environmental stress Lysogenic cycle 2 The phage DNA circularizes Prophage 6

The lysogenic bacterium replicates normally OR 3 Many cell divisions New phage DNA and proteins are synthesized 5 Phage DNA inserts into the bacterial chromosome by recombination Figure 10.17_1

Phage Attaches to cell Phage DNA 4 The cell lyses, releasing phages 1 Bacterial chromosome The phage injects its DNA Lytic cycle Phages assemble

2 3 New phage DNA and proteins are synthesized The phage DNA circularizes Figure 10.17_2 Phage Attaches to cell Phage DNA 1 Bacterial

chromosome The phage injects its DNA 7 Environmental stress Many cell divisions Lysogenic cycle 2 The phage DNA circularizes 5 Prophage

6 The lysogenic bacterium replicates normally, copying the prophage at each cell division Phage DNA inserts into the bacterial chromosome by recombination 10.18 CONNECTION: Many viruses cause disease in animals and plants Viruses can cause disease in animals and plants. DNA viruses and RNA viruses cause disease in animals. A typical animal virus has a membranous outer envelope and projecting spikes of glycoprotein. The envelope helps the virus enter and leave the host cell. Many animal viruses have RNA rather than DNA as

their genetic material. These include viruses that cause the common cold, measles, mumps, polio, and AIDS. 2012 Pearson Education, Inc. 10.18 CONNECTION: Many viruses cause disease in animals and plants The reproductive cycle of the mumps virus, a typical enveloped RNA virus, has seven major steps: 1. 2. 3. 4. 5. entry of the protein-coated RNA into the cell, uncoatingthe removal of the protein coat, RNA synthesismRNA synthesis using a viral enzyme, protein synthesismRNA is used to make viral proteins, new viral genome productionmRNA is used as a

template to synthesize new viral genomes, 6. assemblythe new coat proteins assemble around the new viral RNA, and 7. exitthe viruses leave the cell by cloaking themselves in the host cells plasma membrane. 2012 Pearson Education, Inc. 10.18 CONNECTION: Many viruses cause disease in animals and plants Some animal viruses, such as herpesviruses, reproduce in the cell nucleus. Most plant viruses are RNA viruses. To infect a plant, they must get past the outer protective layer of the plant. Viruses spread from cell to cell through plasmodesmata. Infection can spread to other plants by insects, herbivores, humans, or farming tools. There are no cures for most viral diseases of plants or animals.

Animation: Simplified Viral Reproductive Cycle 2012 Pearson Education, Inc. Figure 10.18 Glycoprotein spike Protein coat Membranous envelope Viral RNA (genome) Plasma membrane of host cell 1 Entry 2

Uncoating 3 RNA synthesis by viral enzyme CYTOPLASM Viral RNA (genome) 4 Protein synthesis 5 mRNA

New viral proteins 6 RNA synthesis (other strand) Template Assembly Exit 7 New viral genome Figure 10.18_1

Glycoprotein spike Protein coat Membranous envelope Viral RNA (genome) Plasma membrane of host cell CYTOPLASM 1 Entry 2 Uncoating

3 RNA synthesis by viral enzyme Viral RNA (genome) Figure 10.18_2 4 Protein synthesis 5 mRNA New

viral proteins 6 RNA synthesis (other strand) Template Assembly Exit 7 New viral genome 10.19 EVOLUTION CONNECTION: Emerging viruses threaten human health Viruses that appear suddenly or are new to medical scientists are called emerging viruses. These

include the AIDS virus, Ebola virus, West Nile virus, and SARS virus. 2012 Pearson Education, Inc. 10.19 EVOLUTION CONNECTION: Emerging viruses threaten human health Three processes contribute to the emergence of viral diseases: 1. mutationRNA viruses mutate rapidly. 2. contact between speciesviruses from other animals spread to humans. 3. spread from isolated human populations to larger human populations, often over great distances. 2012 Pearson Education, Inc.

Figure 10.19 Figure 10.19_1 Figure 10.19_2 10.20 The AIDS virus makes DNA on an RNA template AIDS (acquired immunodeficiency syndrome) is caused by HIV (human immunodeficiency virus). HIV is an RNA virus, has two copies of its RNA genome, carries molecules of reverse transcriptase, which causes reverse transcription, producing DNA from an RNA template. 2012 Pearson Education, Inc. Figure 10.20A

Envelope Glycoprotein Protein coat RNA (two identical strands) Reverse transcriptase (two copies) 10.20 The AIDS virus makes DNA on an RNA template After HIV RNA is uncoated in the cytoplasm of the host cell, 1. reverse transcriptase makes one DNA strand from RNA, 2. reverse transcriptase adds a complementary DNA strand, 3. double-stranded viral DNA enters the nucleus and integrates into the chromosome, becoming a provirus, 4. the provirus DNA is used to produce mRNA,

5. the viral mRNA is translated to produce viral proteins, and 6. new viral particles are assembled, leave the host cell, and can then infect other cells. Animation: HIV Reproductive Cycle 2012 Pearson Education, Inc. Figure 10.20B Reverse transcriptase Viral RNA 1 DNA strand CYTOPLASM NUCLEUS Chromosomal

DNA 2 Doublestranded DNA 3 Provirus DNA 4 5 Viral RNA and proteins

RNA 6 10.21 Viroids and prions are formidable pathogens in plants and animals Some infectious agents are made only of RNA or protein. Viroids are small, circular RNA molecules that infect plants. Viroids replicate within host cells without producing proteins and interfere with plant growth. Prions are infectious proteins that cause degenerative brain diseases in animals. Prions appear to be misfolded forms of normal brain proteins, which convert normal protein to misfolded form. 2012 Pearson Education, Inc. 10.22 Bacteria can transfer DNA in three ways

Viral reproduction allows researchers to learn more about the mechanisms that regulate DNA replication and gene expression in living cells. Bacteria are also valuable but for different reasons. Bacterial DNA is found in a single, closed loop, chromosome. Bacterial cells divide by replication of the bacterial chromosome and then by binary fission. Because binary fission is an asexual process, bacteria in a colony are genetically identical to the parent cell. 2012 Pearson Education, Inc. 10.22 Bacteria can transfer DNA in three ways Bacteria use three mechanisms to move genes from cell to cell. 1. Transformation is the uptake of DNA from the surrounding environment. 2. Transduction is gene transfer by phages. 3. Conjugation is the transfer of DNA from a donor to a

recipient bacterial cell through a cytoplasmic (mating) bridge. Once new DNA gets into a bacterial cell, part of it may then integrate into the recipients chromosome. 2012 Pearson Education, Inc. Figure 10.22A DNA enters cell A fragment of DNA from another bacterial cell Bacterial chromosome (DNA) Figure 10.22B

Phage A fragment of DNA from another bacterial cell (former phage host) Figure 10.22C Mating bridge Sex pili Donor cell Recipient cell Figure 10.22D

Donated DNA Recipient cells chromosome Crossovers Degraded DNA Recombinant chromosome 10.23 Bacterial plasmids can serve as carriers for gene transfer The ability of a donor E. coli cell to carry out conjugation is usually due to a specific piece of DNA called the F factor. During conjugation, the F factor is integrated into the bacteriums chromosome.

The donor chromosome starts replicating at the F factors origin of replication. The growing copy of the DNA peels off and heads into the recipient cell. The F factor serves as the leading end of the transferred DNA. 2012 Pearson Education, Inc. Figure 10.23A-B F factor (integrated) F factor (plasmid) Donor Donor Origin of F replication Bacterial

chromosome F factor starts replication and transfer of chromosome Bacterial chromosome F factor starts replication and transfer Recipient cell Only part of the chromosome transfers Recombination can occur The plasmid completes its

transfer and circularizes The cell is now a donor Figure 10.23A F factor (integrated) Donor Origin of F replication Bacterial chromosome F factor starts replication and transfer of chromosome Recipient cell

Only part of the chromosome transfers Recombination can occur 10.23 Bacterial plasmids can serve as carriers for gene transfer An F factor can also exist as a plasmid, a small circular DNA molecule separate from the bacterial chromosome. Some plasmids, including the F factor, can bring about conjugation and move to another cell in linear form. The transferred plasmid re-forms a circle in the recipient cell. R plasmids pose serious problems for human medicine by carrying genes for enzymes that destroy antibiotics.

2012 Pearson Education, Inc. Figure 10.23B F factor (plasmid) Donor Bacterial chromosome F factor starts replication and transfer The plasmid completes its transfer and circularizes The cell is now a donor Figure 10.23C Plasmids

You should now be able to 1. Describe the experiments of Griffith, Hershey, and Chase, which supported the idea that DNA was lifes genetic material. 2. Compare the structures of DNA and RNA. 3. Explain how the structure of DNA facilitates its replication. 4. Describe the process of DNA replication. 5. Describe the locations, reactants, and products of transcription and translation. 2012 Pearson Education, Inc. You should now be able to 6. Explain how the languages of DNA and RNA are used to produce polypeptides. 7. Explain how mRNA is produced using DNA. 8. Explain how eukaryotic RNA is processed before leaving the nucleus. 9. Relate the structure of tRNA to its functions in

the process of translation. 10. Describe the structure and function of ribosomes. 2012 Pearson Education, Inc. You should now be able to 11. Describe the step-by-step process by which amino acids are added to a growing polypeptide chain. 12. Diagram the overall process of transcription and translation. 13. Describe the major types of mutations, causes of mutations, and potential consequences. 14. Compare the lytic and lysogenic reproductive cycles of a phage. 15. Compare the structures and reproductive cycles of the mumps virus and a herpesvirus. 2012 Pearson Education, Inc. You should now be able to 16. Describe three processes that contribute to the

emergence of viral disease. 17. Explain how the AIDS virus enters a host cell and reproduces. 18. Describe the structure of viroids and prions and explain how they cause disease. 19. Define and compare the processes of transformation, transduction, and conjugation. 20. Define a plasmid and explain why R plasmids pose serious human health problems. 2012 Pearson Education, Inc. Figure 10.UN01 Sugarphosphate backbone A Nitrogenous base G

Phosphate group Sugar Nucleotide C DNA T G C Nitrogenous G bases A T Sugar

DNA Polynucleotide RNA C G A U DeoxyRibose ribose Figure 10.UN02 Growing polypeptide Large ribosomal subunit

Amino acid tRNA Anticodon mRNA Codons Small ribosomal subunit Figure 10.UN03 DNA is a polymer made from monomers called

is performed by an enzyme called (b) (a) (c) (d) RNA comes in three kinds called (e) (f)

(g) is performed by structures called Protein molecules are components of use amino-acid-bearing molecules called (h) one or more polymers made from (i) monomers called

Figure 10.1_UN Figure 10.17_UN Figure 10.18_UN

Recently Viewed Presentations

  • Chapter 2.1

    Chapter 2.1

    Macromolecules are giant molecules made from hundreds or thousands of smaller molecules. The smaller molecules are referred to as . monomers. Monomers join together to make . polymers. The process by which monomers join to make polymers is called ....
  • Cloud in Motion: Dont Be Left Behind: What

    Cloud in Motion: Dont Be Left Behind: What

    By the end of 2016, there will be an estimated 13.3 million mobile workers in Canada, representing 73% of the total workforce. In 2006 (exactly 10 years ago), TELUS introduced Work Styles, a flexible work program that empowers team members...
  • Standard Grade Badminton Crieff High School The Overhead

    Standard Grade Badminton Crieff High School The Overhead

    Standard Grade Badminton ... Example of levers: Try hitting a shuttle with a short racket, then with a long one. Which one were you able to hit the shuttle furthest with? Homework : Fill in sheet, put answers on the...
  • PowerPoint-presentatie

    PowerPoint-presentatie

    Piet Mondriaan, Compositie met geel rood, zwart, blauw en grijs, 1920 c/oPictoright Amsterdam/Stedelijk Museum Amsterdam. Cornelis Jouke Blaauw, voorzittersstoel en vergaderstoel voor School voor Kunstnijverheid in Haarlem waar hij docent Bouwkunde was, 1918-1919. Coll.
  • Becoming a Learning Community - echoesineducation

    Becoming a Learning Community - echoesineducation

    "Victim" Experience. Think of one experience when you felt like a "victim"…what was the feeling like? How did you behave? Focus on the same circumstances, this time think of it as "events in a hero's journey towards learning something new."
  • Begin Exam Five material: Digestive System

    Begin Exam Five material: Digestive System

    During cephalic and gastric. phases, stimulation by. vagal nerve fibers causes. release of pancreatic juice. and weak contractions of. the gallbladder. Upon reaching the. pancreas, cholecystokinin. induces the secretion of. enzyme-rich pancreatic juice; secretin causes copious. secretion of bicarbonate-rich. pancreatic...
  • BASIC SPECTROSCOPY - Weebly

    BASIC SPECTROSCOPY - Weebly

    SPECTROSCOPY. The branch of science concerned with the investigation and . measurement of spectra. produced when matter (Atoms or Molecules) interacts with electromagnetic radiation (EMR). Atoms and molecules interact with electromagnetic radiation (EMR) and . absorb and/or emit . Electro...
  • Wells - typology

    Wells - typology

    Vowel-length is important. Provincial southern Irish English; also Jamaica and Barbados 2 Wells p. 182: Wells - typology Type II: augmented D-system because of R-Dropping. Vowel length. Most accents of England and Wales including RP; Southern Hemisphere accents 3 Wells...