1 Human chromosomes: 50->250 million base pairs. Average gene: 3000 base pairs. <5% of DNA codes for protein.

What is a Gene? Short stretch of DNA on chromosome. Short stretch of DNA on chromosome. Two parts: Two parts: Information in genes used to make proteins. Information in genes used to make proteins. Two Stages: Two Stages: TranscriptionTranscription TranslationTranslation 2 DNA Coding region Regulatory region

Protein Synthesis

4 DNAvs. RNA Double stranded Double stranded Sugar = deoxyribose Sugar = deoxyribose Thymine (no Uracil) Thymine (no Uracil) Stays in nucleus Stays in nucleus One type One type Same copy in the cell all the time Same copy in the cell all the time Single stranded Single stranded Sugar = ribose Sugar = ribose Uracil (instead of Thymine) Uracil (instead of Thymine) Nucleus & cytoplasm Nucleus & cytoplasm 3 types (mRNA, tRNA, rRNA) 3 types (mRNA, tRNA, rRNA) Disposable copies Disposable copies

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6 Ribose vs. Deoxyribose

7 RNA many functions but mostly just protein synthesis many functions but mostly just protein synthesis three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA three main types of RNA: messenger RNA, ribosomal RNA, and transfer RNA

8 Types of RNA

9 mRNA RNA molecules that carry copies of the DNA instructions = mRNA RNA molecules that carry copies of the DNA instructions = mRNA messenger RNA (mRNA) = serve as “messengers” from DNA to the rest of the cell messenger RNA (mRNA) = serve as “messengers” from DNA to the rest of the cell

10 Transcription & Translation

11 Transcription (DNA  mRNA) RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA RNA molecules are produced by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA required enzyme = RNA polymerase required enzyme = RNA polymerase 1. RNA polymerase binds to DNA (in nucleus) 2. separates the DNA strands 3. RNA polymerase then uses one strand of DNA as a template 4. nucleotides are assembled into a strand of mRNA Transcription Animation Transcription Animation Transcription Animation Transcription Animation

TRANSCRIPTION Similar to DNA replication, but different. 1. Copies only one of the two strands. 2. Makes a copy as RNA, not DNA. 12

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14 Where does RNA start? csadaksjdfllasdailsdflRaiseyourhandifyoucanreadthis.aksdjfjasd kjaskklasdjfkkjajdfiodlskj Need punctuation to identify where coding region begins and ends: Need punctuation to identify where coding region begins and ends: promoters - signals in DNA that indicate where the enzyme should bind (“start sequence”). promoters - signals in DNA that indicate where the enzyme should bind (“start sequence”). Similar signals in DNA cause transcription to stop when the new RNA molecule is completed. Similar signals in DNA cause transcription to stop when the new RNA molecule is completed.

15 RNA Editing Intron = intervening sequence of DNA; does not code for a protein Intron = intervening sequence of DNA; does not code for a protein Exon = expressed sequence of DNA; codes for a protein Exon = expressed sequence of DNA; codes for a protein When RNA molecules are formed, both the introns and the exons are copied from the DNA When RNA molecules are formed, both the introns and the exons are copied from the DNA –introns are cut out of RNA molecules while they are still in the nucleus –exons are then spliced back together to form the final mRNA

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17 The Genetic Code Proteins = long chains of amino acids Proteins = long chains of amino acids (polypeptides) (polypeptides) polypeptide = combination of any or all of the 20 different amino acids polypeptide = combination of any or all of the 20 different amino acids properties of proteins are determined by the order in which different amino acids are joined together to produce polypeptides properties of proteins are determined by the order in which different amino acids are joined together to produce polypeptides

18 The “language” of mRNA instructions is called the genetic code The “language” of mRNA instructions is called the genetic code RNA contains four different bases: A, U, C, and G RNA contains four different bases: A, U, C, and G Letters read “3” at a time = codon Letters read “3” at a time = codon Codon = a group of three nucleotides on messenger RNA that specify a particular amino acid. Codon = a group of three nucleotides on messenger RNA that specify a particular amino acid.

19 Translation (mRNA  tRNA  amino acid chain) Occurs at the Ribosome Occurs at the Ribosome mRNA = instructions for the order of the amino acid sequence mRNA = instructions for the order of the amino acid sequence Ribosome = reads the instructions of the mRNA Ribosome = reads the instructions of the mRNA

20 Translation DNA/RNA Adenine Cytosine Guanine Thymine/Uracil Protein(Amino Acid) Alanine Arginine AsparagineAspartate Cysteine Glutamine GlutamateGlycine HistidineIsoleucine Leucine Lysine Methionine Phenylalanine ProlineSerine Threonine Tyrosine Tryptophan Valine

21 rRNA Ribosomes are made up of several dozen proteins, as well as a form of RNA known as ribosomal RNA (rRNA). Ribosomes are made up of several dozen proteins, as well as a form of RNA known as ribosomal RNA (rRNA).

22 tRNA During the construction of a protein, a third type of RNA molecule transfers each amino acid to the ribosome During the construction of a protein, a third type of RNA molecule transfers each amino acid to the ribosome –as specified by coded messages in mRNA. messages in mRNA. These RNA molecules These RNA molecules are known as are known as transfer RNA (tRNA). transfer RNA (tRNA).

23 Identify the players at work

24 Steps of Translation 1. mRNA is released from the nucleus  enters cytoplasm 2. mRNA attaches to the ribosome 3. mRNA codons move through the ribosome  proper amino acid brought by tRNA 4. Amino acids are bound together  polypeptide chain

25 Each tRNA carries only one type of amino acid Each tRNA carries only one type of amino acid The three bases on tRNA = anticodon (complementary to mRNA) The three bases on tRNA = anticodon (complementary to mRNA)

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27 The ribosome forms peptide bonds between the neighboring amino acids The ribosome forms peptide bonds between the neighboring amino acids It also breaks the bonds between tRNA and the amino acids It also breaks the bonds between tRNA and the amino acids Translation ends when a “stop” codon is reached Translation ends when a “stop” codon is reached

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29 Translation Animation Translation Animation

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31 Bases in DNA/RNA form triplet code Second Base UCAG First base U UUUPhe (F)UCU Ser (S) UAU Tyr (Y) UGU Cys (C) U Third base UUCUCCUACUGCC UUALeu (L)UCAUAA Stop UGA Stop A UUGUCGUAG Stop UGG Trp (W) G C CUU Leu (L) CCU Pro (P) CAU His (H) CGU Arg (R) U CUCCCCCACCGCC CUACCACAA Gln (Q) CGAA CUGCCGCAGCGGG A AUU Ile (I) ACU Thr (T) AAU Asn (N) AGU Ser (S) U AUCACCAACAGCC AUAACAAAA Lys (K) AGA Arg (R) A AUGMet (M) Start ACGAAGAGGG G GUU Val (V) GCU Ala (A) GAU Asp (D) GGU Gly (G) U GUCGCCGACGGCC GUAGCAGAA Glu (E) GGAA GUGGCGGAGGGGG Codon Table:

32 What amino acids are made? Use the mRNA strand on the Genetic Code Chart Use the mRNA strand on the Genetic Code Chart DNA: TAC AAA CAC GGA CCA ACT DNA: TAC AAA CAC GGA CCA ACT (coding strand) (coding strand) mRNA: AUG UUU GUG CCU GGU UGA mRNA: AUG UUU GUG CCU GGU UGA tRNA: UAC AAA CAC GGA CCA ACU tRNA: UAC AAA CAC GGA CCA ACU Amino acids: Methionine – Phenylalanine – Amino acids: Methionine – Phenylalanine – Valine - Proline - Glycine - STOP Valine - Proline - Glycine - STOP

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