How Genes Work n Genes on DNA are

Information Flow n Transcription ¨ In n Translation ¨ In n the nucleus the

RNA vs. DNA n n Both are linear nucleotide polymers RNA differs from DNA

Three Types of RNA n Messenger RNA (m. RNA) ¨ Encodes n Transfer RNA

Transcription n n DNA information is copied into RNA Similar to replication with three

Transcription n n RNA polymerase starts at promoter Its complex unwinds DNA It copies

Introns & Exons n n n Eukaryotic cells have non-coding regions in genes (introns)

The Genetic Code n n n Translation of RNA 3 bases = 1 codon

The Genetic Code Possible codons: 4 X 4 = 64 n 20 possible amino

Translation RNA sequence translated into protein sequence n Genetic code used like a dictionary

t. RNA n Two binding sites: ¨ Amino acid site ¨ Anticodon n Amino

Translation Ribosome holds m. RNA n t. RNA binds to first codon n ¨

From Gene to Phenotype Genes are inherited as DNA n DNA is transcribed into

Sickle Cell Anemia Gene for hemoglobin n One base pair change n Causes one

Process Animation 13. 1 The Flow of Genetic Information in a Eukaryotic Cell Windows

Process Animation 13. 3 Translation Windows © 2006 W. W. Norton & Company, Inc.

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How Genes Work n Genes on DNA are used to make RNA ¨ Transcription ¨ If n gene codes for protein, m. RNA is made RNA is used to make proteins ¨ Translation © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 1

RNA vs. DNA n n Both are linear nucleotide polymers RNA differs from DNA ¨ Single stranded ¨ Ribose instead of deoxyribose ¨ U base instead of T © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 3

Three Types of RNA n Messenger RNA (m. RNA) ¨ Encodes n Transfer RNA (t. RNA) ¨ Aids n proteins translation Ribosomal RNA (r. RNA) ¨ Used to make ribosomes © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 4

Transcription n n DNA information is copied into RNA Similar to replication with three differences: ¨ RNA polymerase is used instead of DNA polymerase ¨ Only genes are transcribed not the entire genome ¨ RNA is made instead of DNA © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 5

Transcription n n RNA polymerase starts at promoter Its complex unwinds DNA It copies bases using complimentary base pairing (U v. s. T) Moves down one strand Stops at terminator © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 6

Introns & Exons n n n Eukaryotic cells have non-coding regions in genes (introns) Removed after transcription Exons are connected to produce the mature m. RNA © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 7

The Genetic Code Possible codons: 4 X 4 = 64 n 20 possible amino acids n Most amino acids have more than 1 codon n ¨ Degeneracy of the code ¨ Why many mutations are silent (make no protein change) n (degenerate –having two or more states). Three codons code for no amino acid ¨ STOP codons © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 9

Translation RNA sequence translated into protein sequence n Genetic code used like a dictionary n Ribosome n ¨ Holds m. RNA ¨ Links amino acids together © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 10

t. RNA n Two binding sites: ¨ Amino acid site ¨ Anticodon n Amino Acid Serine Amino Acid attachment site t. RNA Matches the Amino acid with codon Anticodon Codon m. RNA © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 11

Translation Ribosome holds m. RNA n t. RNA binds to first codon n ¨ AUG – start codon = methionine Second t. RNA binds to next codon n Amino acids are linked n Move to next codon n Animation n © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 12

From Gene to Phenotype Genes are inherited as DNA n DNA is transcribed into RNA n RNA is translated into protein n Proteins give the organism traits n ¨ Mutations in DNA produce changes in traits © 2006 W. W. Norton & Company, Inc. DISCOVER BIOLOGY 3/e 13