DNA Replication When a cell or organism reproduces

• Watson and Crick’s model for DNA suggested that DNA replicated by a

THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN • DNA functions

How an Organism’s DNA Genotype Produces Its Phenotype • An organism’s genotype, its genetic

• What is the language of nucleic acids? – In DNA, it is

• DNA specifies the synthesis of proteins in two stages Nucleus DNA Transcription

• When DNA is transcribed, the result is an RNA molecule • RNA

Transcription: From DNA to RNA • In transcription – Genetic information is transferred from

RNA nucleotides RNA polymerase Newly made RNA Direction of transcription Template strand of DNA

• Transcription of an entire gene RNA polymerase DNA of gene Promoter DNA

• RNA processing includes n Exo – Removing introns ron n Exo Intron

• Transcription and translation – Are the processes whereby genes control the structures

• Triplets of bases – Specify all the amino acids – Are called

The Genetic Code • The genetic code is the set of rules relating nucleotide

• The genetic code is shared by all organisms Figure 10. 12 Copyright

Translation: The Players • Translation – Is the conversion from the nucleic acid language

Messenger RNA (m. RNA) • m. RNA – Is the first ingredient for translation

• An m. RNA molecule has a cap and tail that help it

Transfer RNA (t. RNA) • t. RNA – Acts as a molecular interpreter –

• A fully assembled ribosome holds t. RNA and m. RNA for use

• The process of elongation Amino acid Polypeptide P site Anticodon m. RNA

Mutations • A mutation – Is any change in the nucleotide sequence of DNA

Mutagens • Mutations may result from – Errors in DNA replication – Physical or

• DNA can be damaged by ultraviolet light – The enzymes and proteins

• Although mutations are often harmful – They are the source of the

VIRUSES: GENES IN PACKAGES • Viruses sit on the fence between life and nonlife

Bacteriophages • Bacteriophages, or phages – Attack bacteria Head Tail fiber DNA of virus

Plant Viruses • Viruses that infect plants – Can stunt growth and diminish plant

Protein spike VIRUS Protein coat Envelope Viral RNA (genome) Plasma membrane of host cell

Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

Signaling between biomolecules Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• Gene therapy Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

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DNA Replication • When a cell or organism reproduces, a complete set of genetic instructions must pass from one generation to the next Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• Watson and Crick’s model for DNA suggested that DNA replicated by a template mechanism Parental (old) DNA molecule Daughter (new) strand Daughter DNA molecule (double helices) Figure 10. 6 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN • DNA functions as the inherited directions for a cell or organism – How are these directions carried out? Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

How an Organism’s DNA Genotype Produces Its Phenotype • An organism’s genotype, its genetic makeup is the sequence of nucleotide bases in DNA – The phenotype is the organism’s specific traits Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• What is the language of nucleic acids? – In DNA, it is the linear sequence of nucleotide bases DNA molecule Gene 1 Gene 2 Gene 3 DNA strand Transcription RNA Translation Codon Polypeptide Amino acid Figure 10. 10 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• DNA specifies the synthesis of proteins in two stages Nucleus DNA Transcription RNA – Transcription – Translation Protein Cytoplasm Figure 10. 9 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• When DNA is transcribed, the result is an RNA molecule • RNA is then translated into a sequence of amino acids in a polypeptide Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

Transcription: From DNA to RNA • In transcription – Genetic information is transferred from DNA to RNA – An RNA molecule is transcribed from a DNA template Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

RNA nucleotides RNA polymerase Newly made RNA Direction of transcription Template strand of DNA (a) A close-up view of transcription Figure 10. 13 a Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• Transcription of an entire gene RNA polymerase DNA of gene Promoter DNA Initiation RNA Elongation Terminator DNA Area shown in part (a) Termination Growing RNA Completed RNA (b) Transcription of a gene Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings RNA polymerase Figure 10. 13 b

• RNA processing includes n Exo – Removing introns ron n Exo Intron Exon DNA Cap – Adding a cap and tail Int RNA transcript with cap and tail Transcription Addition of cap and tail Tail Introns removed Exons spliced together m. RNA – Splicing exons together Coding sequence Nucleus Cytoplasm Figure 10. 14 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

Transfer RNA (t. RNA) • t. RNA – Acts as a molecular interpreter – Carries amino acids – Matches amino acids with codons in m. RNA using anticodons Amino acid attachment site Hydrogen bond RNA polynucleotide chain Anticodon Figure 10. 15 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• A fully assembled ribosome holds t. RNA and m. RNA for use in translation Next amino acid to be added to polypeptide Growing polypeptide t. RNA m. RNA (b) Figure 10. 16 b Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• The process of elongation Amino acid Polypeptide P site Anticodon m. RNA A site Codons 1 Codon recognition Elongation 2 Peptide bond formation New peptide bond m. RNA movement 3 Translocation Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings Figure 10. 19

Mutations • A mutation – Is any change in the nucleotide sequence of DNA Normal hemoglobin DNA Mutant hemoglobin DNA m. RNA Normal hemoglobin Glu Sickle-cell hemoglobin Val Figure 10. 21 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

• Although mutations are often harmful – They are the source of the rich diversity of genes in the living world – They contribute to the process of evolution by natural selection Figure 10. 23 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

VIRUSES: GENES IN PACKAGES • Viruses sit on the fence between life and nonlife – They exhibit some but not all characteristics of living organisms Figure 10. 24 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

Plant Viruses • Viruses that infect plants – Can stunt growth and diminish plant yields Protein RNA – Can spread throughout the entire plant Figure 10. 27 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings

Protein spike VIRUS Protein coat Envelope Viral RNA (genome) Plasma membrane of host cell m. RNA 1 Entry 2 Uncoating 3 RNA synthesis by viral enzyme 4 Protein synthesis 5 RNA synthesis (other strand) 6 Assembly Template New viral genome New viral proteins Exit 7 Figure 10. 29 Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings