Central Dogma Protein Synthesis 4. Genes are a set of instructions encoded in the DNA sequence of each organism that specify the sequence of amino acids in proteins characteristic of that organism. As a basis for understanding this concept: a. Students know the general pathway by which ribosomes synthesize proteins, using tRNAs to translate genetic information in mRNA. DNA does not leave the cell nucleus, but messenger RNA (mRNA), complementary to DNA, carries encoded information from DNA to the ribosomes (transcription) in the cytoplasm. (The ribosomes translate mRNAs to make protein.) Freely floating amino acids within the cytoplasm are bonded to specific transfer RNAs (tRNAs) that then transport the amino acid to the mRNA now located on the ribosome. As a ribosome moves along the mRNA strand, each mRNA codon, or sequence of three nucleotides specifying the insertion of a particular amino acid, is paired in sequence with the anticodon of the tRNA that recognizes the sequence. Each amino acid is added, in turn, to the growing polypeptide at the specified position. After learning about transcription and translation through careful study of expository texts, students can simulate the processes on paper or with representative models. Computer software and commercial videos are available that illustrate animated sequences of transcription and translation. 4. b. Students know how to apply the genetic coding rules to predict the sequence of amino acids from a sequence of codons in RNA. The sequence of amino acids in protein is provided by the genetic information found in DNA. In prokaryotes, mRNA transcripts of a coding sequence are copied from the DNA as a single contiguous sequence. In eukaryotes, the initial RNA transcript, while in the nucleus, is composed of exons, sequences of nucleotides that carry useful information for protein synthesis, and introns, sequences that do not. Before leaving the nucleus, the initial transcript is processed to remove introns and splice exons together. The processed transcript, then properly called mRNA and carrying the appropriate codon sequence for a protein, is transported from the nucleus to the ribosome for translation. Each mRNA has sequences, called codons, that are decoded three nucleotides at a time. Each codon specifies the addition of a single amino acid to a growing polypeptide chain. A start codon signals the beginning of the sequence of codons to be translated, and a stop codon ends the sequence to be translated into protein. Students can write out mRNA sequences with start and stop codons from a given DNA sequence and use a table of the genetic code to predict the primary sequences of proteins. 4. c. Students know how mutations in the DNA sequence of a gene may or may not affect the expression of the gene or the sequence of amino acids in the encoded protein. Mutations are permanent changes in the sequence of nitrogen-containing bases in DNA (see Standard 5.a in this section for details on DNA structure and nitrogen bases). Mutations occur when base pairs are incorrectly matched (e.g., A bonded to C rather than A bonded to T) and can, but usually do not, improve the product coded by the gene. Inserting or deleting base pairs in an existing gene can cause a mutation by changing the codon reading frame used by a ribosome. Mutations that occur in somatic, or nongerm, cells are often not detected because they cannot be passed on to offspring. They may, however, give rise to cancer or other undesirable cellular changes. Mutations in the germline can produce functionally different proteins that cause such genetic diseases as Tay-Sachs, sickle cell anemia, and Duchenne muscular dystrophy.

Two types of nucleic acids # of strands kind of sugar TRANSCRIPTION DIFFERS FROM REPLICATION IN THAT ONLY 1 STRAND OF THE DNA MOLEUCLE IS TRANSCRIBED AND THAT MEANS THAT THE RESULTING RNA MOLECULE IS SS ALSO MRNA IS SHORT COMPARED TO A LARGE CHROMOSOME bases used

The Importance of Protein Synthesis Specific Roles: Enzyme action Transport Motion Protection Support Communication Regulation Examples: Protein antibodies for immune system Hair, nails, skin Hemoglobin in blood Insulin to regulate blood sugar levels

Central Dogma DNA is the genetic material within the nucleus. Cytoplasm Nucleus DNA DNA is the genetic material within the nucleus. Replication The process of replication creates new copies of DNA. Transcription The process of transcription creates an mRNA using DNA information. RNA The sequence of amino acids in protein is provided by the genetic information found in DNA. In prokaryotes, mRNA transcripts of a coding sequence are copied from the DNA as a single contiguous sequence. In eukaryotes, the initial RNA transcript, while in the nucleus, is composed of exons, sequences of nucleotides that carry useful information for protein synthesis, and introns, sequences that do not. Before leaving the nucleus, the initial transcript is processed to remove introns and splice exons together. The processed transcript, then properly called mRNA and carrying the appropriate codon sequence for a protein, is transported from the nucleus to the ribosome for translation. Each mRNA has sequences, called codons, that are decoded three nucleotides at a time. Each codon specifies the addition of a single amino acid to a growing polypeptide chain. A start codon signals the beginning of the sequence of codons to be translated, and a stop codon ends the sequence to be translated into protein. Students can write out mRNA sequences with start and stop codons from a given DNA sequence and use a table of the genetic code to predict the primary sequences of proteins. Translation The process of translation creates a protein using mRNA information. Protein

Protein Synthesis Transcription Translation

Transcription The new RNA molecule is formed by incorporating nucleotides that are complementary to the template strand. DNA DNA coding strand 5’ G T C A T T C G G 3’ G RNA 5’ U C A 3’ 3’ CALLED TRANSCRIPTION BECAUSE THE NUCLEIC ACID LANGUAGE OF DNA HAS TO BE REWRITTEN AS A SEQUENCE OF BASES ON RNA ACTIVATED GENES DO NOT LEAVE THE NUCLEUS BECAUSE THE CYTOPLASM IS TOO HOSTIL INSTEAD A MESSAGE IS CARRIED ON A STRAND OF MRNA THE PROCESS OF MRNA FORMATION IS CALLED TRANSCRIPTION BECAUSE IN THE NUCLEUS THE MRNA IS TRANSCRIBED FROM THE DNA TEMPLATE C A G T A A G C C 5’ DNA template strand

Where to Begin

Production of mRNA copy of the DNA gene Transcription Production of mRNA copy of the DNA gene

Translation The process of reading the RNA sequence of an mRNA and creating the amino acid sequence of a protein is called translation. DNA T C A G template strand Transcription mRNA A G U C Messenger RNA Codon Translation THE GENETIC INSTRUCTIONS FOR THE AA SEQUENCE OF A POLYPEPTIDE CHAIN ARE WRITTEN IN DNA AND TRANSCRIBED TO RNA AS A SERIES OF 3 BASE WORDS CALLED CODONS TRIPLETS IN THE DNA ARE TRANSCRIBED INTO COMPLEMENTARY 3 BASE CODONS IN THE MRNA AND THEN THE MRNA CODONS ARE TRANSLATED INTO AA THAT WILL MAKE UP A POPYPEPTIDE Protein Lysine Serine Valine Polypeptide (amino acid sequence)

INITIATION OF TRANSLATION BRINGS TOGETHER A SMALL RIBOSOMAL SUBUNIT, MRNA AND AN INITIATIOR T RNA AND ALIGNS THEM IN THE PROPER ORIENTATION TO BEGIN TRANSLATION

Codon Translation will always begin with a start codon “AUG” (Start) and end with the “TAG” (end)

Translation Termination Stop codon Ribosome reaches stop codon mRNA 5’ U C G A U A C U G Arg C U A PROTEIN RELEASE FACTOR BONDS TO THE STOP CODON AND RELEASES THE COMPLETED PROTEIN FROM THE TRNA Release factor P Met Gly Cys Lys A

Translation Termination Once stop codon is reached, elements disassemble. U C G A C U G Release factor P THE COMPLETED PP IS FREEDED FROM THE RIBOSOME THE RIBOSOMAL SUBUNITS DETACH AND THE MRNA MAY MOVE ON TO START THE PROCESS ALL OVER AGAIN THE ENTIRE PROCESS OF TRANSLATION TAKES ABOUT 20 SECONDS Met Gly Cys Lys Arg A

EACH POLYRIBOSOME CONSISTS OF ONE STRAND OF MRNA THAT IS BEING READ SIMULTANEOUSLY BY A NUMBER OF RIBOSOMES POLYRIBOSOMES GREATLY INCREASE THE RATE OF PROTEIN SYNTHESIS BECAUSE A SINGLE STRAND OF MRNA CAN PRODUCE MANY PROTEIN MOLEUCLES IN A SHORT TIME THIS IS HOW THE GENOTYPE PRODUCES THE PHENOTYPE CHAPERONE PROTEIN HELP FOLD THE PP INTO ITS 3 D FORM GO OVER PICTURE

Who am I? Messenger RNA a.k.a. mRNA Copied from DNA, conveys information from chromosomes to ribosomes. Every three nucleotides is a codon.

Transports amino acids to ribosomes. Who am I? Transfer RNA a.k.a. tRNA Transports amino acids to ribosomes.

Subunits where the protein is assembled Who am I? Ribosomal RNA a.k.a. rRNA Subunits where the protein is assembled

Synthesis of proteins by ribosomes Translation Synthesis of proteins by ribosomes

Genes Genes: a set of instructions encoded in the DNA sequence of each organism that specify the sequence of amino acids in proteins characteristic of that organism. In eukaryotes, many general are interrupted by introns and exons. Introns – long segments of nucleotides that have no coding information. Exons – are the portions of a gene that are translated (expressed) into proteins.

Protein Synthesis General Pathway

Prokaryotes vs Eukaryotes Protein Synthesis In prokaryotes, mRNA transcripts of a coding sequence are copied from the DNA as a single contiguous sequence. Eukaryotes The initial RNA transcript, while in the nucleus, is composed of exons, and introns. Before leaving the nucleus, introns are removed and splice exons together. The processed transcript, then properly called mRNA and carrying the appropriate codon sequence for a protein, is transported from the nucleus to the ribosome for translation.

Tay-Sachs A baby with Tay-Sachs disease appears healthy at birth. Symptoms usually first appear 3 to 6 months after birth, beginning with mild motor weakness and occasional twitches of the eye (myoclonic jerks). By 6 to 10 months of age, the baby's motor skills may be lost. After this, the diseases progresses rapidly to seizures, blindness, paralysis, and death at age 4 to 5.

Mutations Mutations are permanent changes in the sequence of nitrogen-containing bases in DNA. Mutations occur when base pairs are incorrectly matched (e.g., A bonded to C rather than A bonded to T) and can, but usually do not, improve the product coded by the gene. Inserting or deleting base pairs in an existing gene can cause a mutation by changing the codon reading frame used by a ribosome.

Mutations that occur in somatic, or nongerm, cells are often not detected because they cannot be passed on to offspring. They may, however, give rise to cancer or other undesirable cellular changes. Mutations in the germline can produce functionally different proteins that cause such genetic diseases as Tay-Sachs, sickle cell anemia, and Duchenne muscular dystrophy. Tay-Sachs picture Sickle Cell Anemia Duchenne muscular dystrophy

Duchenne muscular dystrophy In individuals with the disorder, initial findings may include an unusual, waddling manner of walking (gait); difficulty climbing stairs or rising from a sitting position; and repeated falling.

Duchenne muscular dystrophy If it gets worse more problems can occur like Progressive curvature of the spine Wasting of thigh muscles and abnormal enlargement of the calves Abnormal fixation of certain joints (joint contractures) due to muscle weakness Prolonged immobility Shortening of muscle fibers By approximately age 10 to 12, most affected individuals require the use of a wheelchair.

Warm-Up The DNA in each of your cells are exactly alike. How come so many of your cells look completely different? Now talk to the person sitting next to you and see what they came up with. What does trans mean? What does scribe mean? What would transcribe mean? Look for example of genetic mutations Adaptations

Structure of DNA DNA Base Pairing Rules A T C G