DNA and Protein Synthesis What are proteins? What’s the big deal anyway?

DNA Replication Before a cell can divide by mitosis or meiosis, it must first make a copy of its chromosomes. The DNA in the chromosomes is copied in a process called DNA replication. Without DNA replication, new cells would have only half the DNA of their parents. DNA Replication

The blue strands represent the original DNA strands. DNA Replication The blue strands represent the original DNA strands. The red strands are the new, synthesized strands. DNA Replication Replication DNA Replication

DNA Replication https://www.youtube.com/watch?v=zdDkiRw1PdU

Why are proteins important? List as many reasons as you can.

Genes and Proteins The sequence of nucleotides in DNA contain information that is put to work through the production of proteins. Proteins fold into complex, three-dimensional shapes to become key cell structures and regulators of cell functions. Genes and Proteins

Genes and Proteins Some proteins become important structures, such as the filaments in muscle tissue. Other proteins, such as enzymes, control chemical reactions that perform key life functions— breaking down glucose molecules in cellular respiration, digesting food, or making spindle fibers during mitosis. Genes and Proteins

In fact, enzymes control all the chemical reactions of an organism. Genes and Proteins In fact, enzymes control all the chemical reactions of an organism. Thus, by encoding the instructions for making proteins, DNA controls cells. Genes and Proteins

Remember, proteins are polymers of amino acids. Genes and Proteins Remember, proteins are polymers of amino acids. The sequence of nucleotides in each gene contains information for assembling the string of amino acids that make up a single protein. Genes and Proteins

How does DNA tell the cell which protein to make? RNA RNA is a little different than DNA: RNA has the sugar ribose instead of deoxyribose. RNA is only a single strand. RNA contains the nitrogenous base uracil instead of thymine. * Uracil bonds with adenine.

RNA is the BLUEPRINT Architect DNA Blueprint RNA Workers Ribosomes Use bricks to Use amino acids to build buildings build proteins

3 types of RNA 1. mRNA – messenger RNA- carries instructions to build protein to the ribosome. 2. rRNA – ribosomal RNA – what the ribosome is made of. Reads the instructions 3. tRNA – transfer RNA- picks up the amino acids and brings them to the rRNA to build the protein.

2 Events of Protein Synthesis TRANSCRIPTION – The instructions from DNA are copied (transcribed)into a mRNA molecule which carries the instructions from the nucleus to the ribosome. (occurs in nucleus) TRANSLATION – The instructions are read (translated) by the ribosome. A tRNA molecule is sent to pick up and deliver the correct amino acid to the ribosome so it can build the protein(occurs at ribosome)

Transcription: An enzyme, helicase… “unzips” part of the double helix.

Transcription: 2. There is a “start” and “stop” sequence in the DNA to tell the mRNA where to start and stop. UGA = stop AUG = start UAA = stop UAG = stop

Transcription: 3. RNA nucleotides pair up to DNA nitrogenous bases and…bond in a chain

Transcription: The mRNA travels to the ribosome, where the protein will be assembled. (Note: DNA never leaves the nucleus!)

Transcription The main difference between transcription and DNA replication is that transcription results in the formation of one single-stranded RNA molecule rather than a double-stranded DNA molecule. https://www.youtube.com/watch?v=ztPkv7wc3yU Transcription

Transcription DNA strand RNA strand Transcription

In your own words explain transcription

Translation takes place at the ribosomes in the cytoplasm. The process of converting the information in a sequence of nitrogenous bases in mRNA into a sequence of amino acids in protein is known as translation. Translation takes place at the ribosomes in the cytoplasm. https://www.youtube.com/watch?v=8dsTvBaUMvw Translation

Translation In prokaryotic cells, which have no nucleus, the mRNA is made in the cytoplasm. In eukaryotic cells, mRNA is made in the nucleus and travels to the cytoplasm. Translation

TRANSLATION 5. When mRNA binds to the ribosome,… production of a protein begins

A sequence of three nitrogenous bases makes a codon. Each codon is a code for one of 20 amino acids! There are 64 different combinations of three letters, so there are 64 different codons. Some amino acids have more than one code.

TRANSLATION 6. The mRNA code is read and converted into a specific amino acid sequence in a protein chain. 7. This process continues until… a functional protein is made. https://www.youtube.com/watch?v=NJxobgkPEAo

Amino Acid Codon Chart

In your own words explain translation

Replication = copying DNA Transcription = using DNA to make RNA Summary Replication = copying DNA Transcription = using DNA to make RNA Translation = using RNA to make protein The Role of tRNA