Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings When a cell or organism...
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Transcript of Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings When a cell or organism...
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• When a cell or organism reproduces, a complete set of genetic instructions must pass from one generation to the next
DNA Replication
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Watson and Crick’s model for DNA suggested that DNA replicated by a template mechanism
Figure 10.6
Parental (old)DNA molecule
Daughter(new) strand
DaughterDNA molecule(double helices)
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• DNA functions as the inherited directions for a cell or organism
THE FLOW OF GENETIC INFORMATION FROM DNA TO RNA TO PROTEIN
– How are these directions carried out?
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• An organism’s genotype, its genetic makeup is the sequence of nucleotide bases in DNA
How an Organism’s DNA Genotype Produces Its Phenotype
– 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
Figure 10.10
DNA molecule
Translation
Polypeptide
Gene 1
Gene 2
Gene 3
DNA strand
Transcription
RNA
Codon
Amino acid
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• DNA specifies the synthesis of proteins in two stages
– Transcription
– Translation
Figure 10.9
DNANucleus
Transcription
RNA
Translation
ProteinCytoplasm
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
Figure 10.13a
RNApolymerase
RNA nucleotides
Newly madeRNA Direction of
transcriptionTemplatestrand of DNA
(a) A close-up view of transcription
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Transcription of an entire gene
Figure 10.13b
RNA polymerase
DNA of gene
PromoterDNA Initiation Terminator
DNA
RNAElongation
Area shownin part (a)
TerminationGrowingRNA
Completed RNA
RNApolymerase
(b) Transcription of a gene
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• RNA processing includes
– Adding a cap and tail
– Removing introns
– Splicing exons together
Figure 10.14
DNA
RNAtranscriptwith capand tail
mRNA
Exon Intron ExonIntron Exon
Cap
Introns removed Tail
Exons spliced together
Coding sequence
Nucleus
Cytoplasm
TranscriptionAddition of cap and tail
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Transcription and translation
– Are the processes whereby genes control the structures and activities of cells
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Triplets of bases
– Specify all the amino acids
– Are called codons
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• The genetic code is the set of rules relating nucleotide sequence to amino acid sequence
The Genetic Code
Figure 10.11
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• The genetic code is shared by all organisms
Figure 10.12
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Translation
Translation: The Players
– Is the conversion from the nucleic acid language to the protein language
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• mRNA
Messenger RNA (mRNA)
– Is the first ingredient for translation
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• An mRNA molecule has a cap and tail that help it bind to the ribosome
Figure 10.17
Start of genetic message
CapEnd
Tail
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• tRNA
Transfer RNA (tRNA)
– Acts as a molecular interpreter
– Carries amino acids
– Matches amino acids with codons in mRNA using anticodons
Figure 10.15
Amino acid attachment site
Hydrogen bond
RNA polynucleotide chain
AnticodonAnticodon
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• A fully assembled ribosome holds tRNA and mRNA for use in translation
Figure 10.16b
Next amino acidto be added topolypeptide
Growingpolypeptide
mRNA
tRNA
(b)
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Polypeptide
Amino acid
P site
AnticodonmRNA A site
Codons
Elongation
2
3 Translocation
Codon recognition
Peptide bond formation
• The process of elongation
Figure 10.19
mRNAmovement
New peptidebond
1
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• A mutation
Mutations
– Is any change in the nucleotide sequence of DNA
Figure 10.21
Normal hemoglobin Sickle-cell hemoglobin
Glu Val
Normal hemoglobin DNA Mutant hemoglobin DNA
mRNA mRNA
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Mutations may result from
Mutagens
– Errors in DNA replication
– Physical or chemical agents called mutagens
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• DNA can be damaged by ultraviolet light
– The enzymes and proteins involved in replication can repair the damage
Figure 10.7
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 sit on the fence between life and nonlife
VIRUSES: GENES IN PACKAGES
– They exhibit some but not all characteristics of living organisms
Figure 10.24
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Bacteriophages, or phages
Bacteriophages
– Attack bacteria
Figure 10.25
Head
Tail
Tail fiber
DNA of virus
Bacterialcell
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Viruses that infect plants
Plant Viruses
– Can stunt growth and diminish plant yields
– Can spread throughout the entire plant
Figure 10.27
Protein RNA
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Figure 10.29
VIRUS
Entry1
2
3
4
Uncoating
RNA synthesisby viral enzyme
5 RNA synthesis(other strand)
Proteinsynthesis
6 Assembly
7
Exit
Viral RNA (genome)
Protein spike
Protein coat
Envelope
Plasma membrane of host cell
mRNA
New viral proteins
Template
New viral genome
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
Signaling between biomolecules
QuickTime™ and aCinepak decompressor
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Copyright © 2004 Pearson Education, Inc. publishing as Benjamin Cummings
• Gene therapy