Bellringer-January 12, 2015 DNA Complementary – ATGATC ACC TAA DNA Template - mRNA - Amino Acid Seq- FILL IN THE DNA TEMPLATE, mRNA, and Amino Acid sequence (put the 3’ and 5’ to the DNA and mRNA sequences)

Protein Synthesis 3 major processes: – Replication → DNA copied to form 2 new DNA molecules Nucleus – Transcription → DNA info copied to RNA Nucleus – Translation → building a protein according to RNA instructions Cytoplasm

RNA & Transcription From Gene to Protein (DNA  RNA  Protein) Honors Biology Ms. Kim

DNA  RNA  Protein You are now familiar with DNA structure and how new cells are reproduced and DNA is replicated in this process We know DNA contains all the information necessary to make us who we are – But how?? – We have genes…but how do they work? Now we will look into how DNA provides the necessary information to produce proteins.

The Flow of Genetic Information DNA – information in a specific sequence (order) of nucleotides along 2 DNA strands – Leads to specific traits by controlling the synthesis of proteins Gene expression includes two stages – Transcription: DNA  RNA “transcribe” = to copy into another form – Translation: RNA  polypeptide (proteins) – “translate” = to change into another language

Proteins  Proteins are the most versatile macromolecules in living systems and serve crucial functions in essentially all biological processes such as:  Function as catalysts  Transport and store other molecules such as oxygen  Provide mechanical support and immune protection  Generate movement  Transmit nerve impulses  Control growth and differentiation.

How is Protein Made? Cells are controlled by a cellular chain of command – DNA  RNA  protein Called the “Central dogma of biology” What are proteins made out of? – Amino acids There are 20 different amino acids – building blocks of proteins All living things use the same 20 amino acids to make proteins!!!

Breaking down the genetic code DNA Humans have 23 pairs of chromosomes These chromosomes are long chains of bases (A’s, T’s, C’s, and G’s) The bases make up the thousands of genes on each chromosome – So genes gives us specific traits based up the sequence of A’s, T’s, C’s, and G’s – Genes are instructions on how to make proteins which essentially control what we look like and daily functions RNA Remember DNA cannot leave the nucleus, so we need something else to carry the information of the DNA from the nucleus to the cytoplasm of the cell It is RNA’s job to copy DNA’s information and then interpret it to make proteins

CENTRAL DOGMA stored informationworking copyfunctional molecule DNARNA Protein TranscriptionTranslation

Basic Principles of Transcription and Translation Gene (portion of DNA) is copied Transcription – the synthesis of RNA from DNA (DNA  mRNA) – Produces messenger RNA (mRNA). mRNA copies a portion of DNA strand (gene) – Occurs in the nucleus of eukaryotes and leaves nucleus to direct making of protein The mRNA is read to make specific amino acid sequences Translation (happens later) – Nucleic Acid information into Amino Acids. Each Amino Acid as a specific 3 base CODON that codes for it. – actual synthesis of a protein (polypeptide. mRNA  protein (polypeptide) – Occurs on ribosomes

What is transcription? Process of copying DNA (the template strand) into a complementary RNA strand Occurs in the nucleus Similar to DNA replication, but Uracil (U) replaces Thymine (T)

Why RNA? RNA – Ribonucleic Acid How does DNA get out of the nucleus and go to the ribosomes where the proteins are made? – It can’t! DNA cannot leave the nucleus! – So, it copies itself into RNA and that leaves and goes to the ribosomes EXAMPLE – library book, photocopy

What are the characteristics of RNA? Ribose Nucleic Acid Single stranded Made of sugars (called ribose), phosphate groups and nitrogen bases Backbone = alternating ribose sugar/phosphates held together by PHOSPHODIESTER BONDS Made of RNA nucleotides Contains bases: (A) Adenine (G)Guanine (C) Cytosine (U) Uracil (replaces Thymine)

DNA vs. RNA: Sugars = – DNA – deoxyribose – RNA – ribose Nitrogen bases = – DNA – A, C, G and thymine (T) – RNA – A, C, G and uracil (U) Location = – DNA – inside nucleus only – RNA – in and out of nucleus Stranded = – DNA – Double stranded – RNA – Single stranded

RNA: Ribose sugar Deoxyribose means deoxygenated (its lacks an oxygen) Ribose does not lack an oxygen

The 3 major types of RNA Messenger RNA (mRNA) Ribosomal RNA (rRNA) Transfer RNA (tRNA)

Type of RNAFunction JobPicture mRNA (messenger RNA) Brings message from DNA (DNA instructions) to ribosome to make protein tRNA (transfer RNA) Transfers/moves amino acids to ribosomes rRNA (ribosomal RNA) Makes up part of the ribosomes

Messenger RNA mRNA copies the DNA code and carries it into the cytoplasm where protein synthesis happens Notice how the bases of mRNA are organized into codons A codon consists of 3 consecutive bases  code for a specific amino acid Remember a chain of amino acids = a protein So….DNA codes for proteins!

The Genetic Code It’s a table used that TRANSLATES RNA nucleotides (or mRNA “letters”) into one of the 20 amino acids – 3 letter mRNA “word” = 1 amino acid – There are 4 different RNA “letters” that can be used A, U, C, and G

Codons: Triplets of Bases Genetic information is coded as a sequence of base triplets, or codons 3 letter mRNA “words” = codon – FOUND ONLY ON mRNA Codons must be read in the correct order – For specified polypeptide to be produced – Always read in the 5’  3’ direction

THE GENETIC CODE

Evolution of the Genetic Code The genetic code is nearly universal – Shared by organisms from the simplest bacteria to the most complex animals All organisms have SAME DNA “letters” and SAME RNA “letters”

During transcription, a gene determines the sequence of bases along length of mRNA. Figure 17.4 DNA molecule Gene 1 Gene 2 Gene 3 DNA strand (template) TRANSCRIPTION mRNA Protein TRANSLATION Amino acid ACC AAACCGAG T UGG U UU GGCUC A Trp Phe Gly Ser Codon

Transcription DNA  RNA RNA synthesis is done by RNA polymerase Forces DNA strands apart (breaks H bonds btw bases) and hooks together RNA nucleotides Follows same DNA base-pairing rules, except in RNA, uracil substitutes for thymine – A = U (T on DNA = A in RNA) – C = G

Synthesis of an RNA Transcript Initiation – DNA strands unwind – RNA polymerase initiates mRNA synthesis at start point on templates called promoters – RNA polymerase binds to promoter (certain base sequence (TATA box)) Elongation – RNA polymerase moves downstream, unwinding DNA & elongating mRNA transcript 5  3 direction. Makes complementary RNA strand to only one side of DNA. – In wake of transcription, DNA strands re-form a double helix. Termination – mRNA transcript is released at terminator signal – RNA polymerase detaches from the DNA

RNA is made in the 5’-3’ direction The DNA template read in the 3’-5’ direction

Template strand = antisense strand Coding strand = sense strand

RNA Polymerase Binding and Initiation of Transcription Promoters (on DNA) starts RNA synthesis (BOTH prokaryotes & eukaryotes) – RNA polymerase binds here then unwinds DNA – RNA Polymerase adds new FREE RNA nucleotides to DNA template strand in 5’  3’ direction – “TATA box” = start signal on DNA promoter Determines which strand is used as template  only 1 side is used at a time!

Transcription Animation nimat/molgenetics/transcription.swf nimat/molgenetics/transcription.swf V CELL /student_view0/chapter3/animation__ mrna_synthesis__transcription___quiz_1_.ht ml

Elongation RNA polymerase Non-template strand of DNA RNA nucleotides 3 end C A E G C A A U T A G G T T A A C G U A T C A T CCA A T T G G Newly made RNA Direction of transcription (“downstream”) Template strand of DNA

Split Genes and RNA Splicing RNA splicing and RNA Modification – Removes introns and joins exons Introns = non-coding regions Exons = coding regions that EXIT nucleus Figure TRANSCRIPTION RNA PROCESSING DNA Pre-mRNA mRNA TRANSLATION Ribosome Polypeptide 5 Cap Exon Intron 5 3 Poly-A tail Introns cut out and exons spliced together Coding segment 5 Cap UTR 5 UTR mRNA Exon Intron Mature mRNA Pre-mRNA

RNA splicing is carried out by spliceosomes in some cases RNA transcript (pre-mRNA) Exon 1 Intron Exon 2 Other proteins Protein snRNA snRNPs Spliceosome components Cut-out intron Mature mRNA Exon 1 Exon Called small nuclear RNA + proteins (ribonucleoproteins)

mRNA Codons Lets Practice: CCA AGA GUG UGA AUG

Practice Coding DNA Complementary – A T C DNA Template - A G A mRNA - U A G Amino Acid Seq-Ile-Ser-Stop T C T U C U T A G A U C A T C T A G

The Ribosome Part of cell where translation (protein synthesis) occurs Where proteins are actually made

Ribosomal RNA Ribosomal RNA (rRNA) - ribosome attaches itself to mRNA Provides the stabilizing structure to hold all substances in position as the protein is synthesized. Contains the enzymes necessary for protein synthesis.

rRNA with attached mRNA and tRNA and forming protein

Transfer RNA Transfer RNA (tRNA) - reads the mRNA code and carries the amino acid to be incorporated into the developing protein – Notice the 3 bases at the bottom of the tRNA which make up the anticodon The anticodon base pairs with the mRNA codon – At the top an amino acid is attached to the tRNA