How can DNA be used by the cell to make a protein? Protein Synthesis How can DNA be used by the cell to make a protein?

DNA Replication Review Draw the complimentary strand of DNA GCT TAG ACT GGC Where (in the cell) does replication occur? What does it produce? What are the 4 nitrogenous bases in DNA? When in the cell does DNA replication occur? Why does DNA need to double?

Importance of protein synthesis? Every inherited trait is controlled by one or more proteins. Protein synthesis is the process that makes these proteins.

Fill It In … What is a trait? How are the terms “protein” and “trait” related?

Importance of protein synthesis? Each cell must produce different proteins based on the function of that cell. For example, only blood cells need to produce the protein hemoglobin.

Central Dogma of Biology The central axis around which all other biological concepts rotate.

Central Dogma of Biology DNA structure controls the production of proteins. A section of DNA which is used as the blueprint or code for the production of a protein is a gene

Central Dogma of Biology Each gene is composed of a specific sequence of nucleotides. This sequence can be represented by writing the order of nitrogen bases. For example, ACGCCATGCTAC

Central Dogma of Biology Every three bases in this sequence is called a codon. A codon is like a single word in a sentence. Only by putting the words (codons) in the correct order can you create a meaningful sentence (protein)

Central Dogma of Biology Proteins are made of amino acids. Each codon directs the cell to place a specific amino acid in a particular position as the protein is built.

Central Dogma of Biology For example, the codon CAA in DNA codes for the amino acid “valine”. If this codon was the third codon in a gene, valine would be the third amino acid in the protein. DNA: TAC GGT CAA AAA met pro val phe

Central Dogma of Biology Diagram of the Central Dogma DNA RNA Protein (transcription) (translation)

Fill It In … Three DNA nucleotides makes a ______. One codon controls the placement of one _______ _______. Many amino acids make a _________.

Fill It In … Rewrite the “Central Dogma” as a sentence (use all of the words!)

Process of protein synthesis Transcription rewrites the DNA code as messenger RNA.

Process of protein synthesis DNA cannot leave the nucleus (it is far too big) to go to the ribosomes where proteins are made. Thus, it must send the instructions using RNA.

Process of protein synthesis mRNA copies the DNA when the DNA unzips one sections called a gene. One gene makes one protein.

Process of protein synthesis messenger RNA is constructed one nucleotide at a time using one side of the DNA as a template

Process of protein synthesis All RNA has a different sugar (ribose) which cannot bond to thymine. Thus, RNA must use a different nitrogen base (uracil) as a substitute for thymine.

Process of protein synthesis For example, if the DNA side read CTA, the mRNA would read GAU. DNA: CTA mRNA: GAT GAU

Process of protein synthesis mRNA leaves the nucleus through a small opening in the nuclear membrane called a pore. The DNA rezips the gene. From RNA to Protein Synthesis

Fill It In … How does transcription produce a “script” based on DNA?

Fill It In … Highlight the mRNA. Explain the diagram.

Transcription happens in the nucleus. An RNA copy of a gene is made. Then the mRNA that has been made moves out of the nucleus into the cytoplasm Once in the cytoplasm, the mRNA is used to make a protein Cytoplasm of cell Nucleus DNA mRNA

How does mRNA tell the cell what to do? Amino Acids Protein How does mRNA tell the cell what to do? mRNA is a message that codes for a protein Proteins are made in the cytoplasm and then work to keep the cell alive Translation (protein synthesis): Process of making a protein Proteins are made up of amino acids (small building blocks) There are 20 different types of amino acids

Process of protein synthesis Translation uses the mRNA to build a protein.

Process of protein synthesis In the cytoplasm of the cell, translation occurs at the ribosome. Ribosomes are made of rRNA (ribsomal RNA) and proteins.

Process of protein synthesis The mRNA “start” codon (AUG) attaches to the ribosome. The ribosome holds mRNA in place and helps link amino acids together to make a protein.

Process of protein synthesis tRNA (transfer RNA) is a molecule that carries an amino acid to the ribsomes. In order for the tRNA to leave the amino acid at the ribosome, it must bond with a codon on the mRNA.

Process of protein synthesis The ribosome allows the tRNA anticodon (made of three bases at the bottom of each tRNA) and the complementary mRNA codon to pair.

Process of protein synthesis The amino acid is removed from the tRNA by an enzyme. As each new amino acid arrives on the tRNA, amino acids are bonded together IN ORDER by a peptide bond to form a polypeptide.

Process of protein synthesis When the ribosome reaches a “stop” codon, it releases the mRNA and the string of amino acids separately. The string of amino acids folds and coils to shape the protein.

Fill It In … How does translation “read” the “script” produced in transcription?

Fill It In … Highlight the protein. Explain this diagram.

Result of protein synthesis Cells respond to their environment by producing different types and amounts of protein.

Result of protein synthesis The cell produces proteins that are structural (forming part of the cell materials) or functional (such as enzymes, hormones, or chemicals for cell chemistry)

Fill It In … What is the END RESULT of protein synthesis?

Result of protein synthesis All of an organism’s cells have the same DNA, but the cells differ based on the expression of the genes.

Result of protein synthesis Multicellular organisms begin as undifferentiated masses of cells. Variation in DNA activity determines cell types.

Result of protein synthesis Different types of cells expressing different genes leads to differentiation. Only specific parts of DNA are activated in those cells.

Result of protein synthesis Once a cell differentiates, the process cannot be reversed. For example, we have muscle cells, nerve cells, and others.

Result of protein synthesis On Epigentics Result of protein synthesis Gene regulation is the process which determines which genes will be expressed (used to make a protein). This can be affected by the cell’s history and/or environment (g+e=p) Proteins may be overproduced, underproduced or produced at incorrect times Ex: injury repair or cancer

Fill It In … If gene regulation were not possible, would cell specialization happen? Why/why not?

Result of protein synthesis Each individual is a sexually reproducing population has slightly different sequences of nucleotides in DNA when compared to other organims of the same specie. The different sequences lead to different proteins, which produce different traits (i.e. variation) For example, two humans with different eye color

Check Yourself! What controls inherited traits? What controls the production of proteins? Define a gene. Diagram the central dogma of biology. What is the purpose of transcription? What type of RNA is used in transcription? What nitrogen base in RNA is used as a substitution for thymine? What is the purpose of translation? What two types of RNA are used only in translation? What type of bond links amino acids.

Check Yourself! What controls inherited traits? ONE OR MORE PROTEIN

Check Yourself! What controls the production of proteins? PROTEIN SYNTHESIS OR DNA

Check Yourself! Define a gene. A SECTION OF DNA THAT CODES FOR A SPECIFIC TRAIT OR PROTEIN

Check Yourself! Diagram the central dogma of biology.

Check Yourself! What is the purpose of transcription? TO MAKE A COPY OF DNA

Check Yourself! What type of RNA is used in transcription? mRNA OR MESSENGER RNA

Check Yourself! What nitrogen base in RNA is used as a substitution for thymine? URACIL

Check Yourself! What is the purpose of translation? TO PRODUCE A PROTEIN

Check Yourself! What two types of RNA are used only in translation? rRNA OR RIBOSOMAL RNA AND tRNA OR TRANSFER RNA

Check Yourself! 10. What type of bond links amino acids. PEPTIDE BOND

Let’s practice … DNA: TAC AAT CGC mRNA: a.a.: DNA: TAC GCG ATT

Process of Translation Nucleus mRNA moves out of nucleus and into cytoplasm Cytoplasm mRNA attaches to a ribosome Ribosome Transfer RNA (tRNA) decodes the mRNA and brings amino acids to build up the protein Amino acid tRNA Anticodon (3 bases on tRNA): Matches up to codons on mRNA Protein (chain of amino acids) detaches from ribosome and goes off to work in the cell