Protein Synthesis

Proteins! https://www.youtube.com/watch?v=suN-sV0cT6c

The Genetic Code RNA has four bases: adenine, cytosine, guanine, and uracil. These bases form a “language”: A, C, G, and U. Ask: What is the genetic code and how is it read? Answer: The four bases of RNA form the “language” called the genetic code. The genetic code is read three “letters” at a time, so that each “word” is three bases long and corresponds to a single amino acid. Remind students that the four bases of RNA are adenine, cytosine, guanine, and uracil. Click to highlight these in the legend.

Protein Synthesis DNA holds the code for protein synthesis but it cannot leave the nucleus. The cell uses RNA to copy the code from DNA and bring it to the ribosomes RNA (ribonucleic acid) has three parts: Simple sugar (ribose) Phosphate group Nitrogen base (adenine, cytosine, guanine, and uracil) There is no thymine in RNA – it is replaced with uracil

RNA Ribonucleic Acid (RNA) Sugar + Phosphate Backbone Differs from DNA Single Stranded Ribose Sugar Base Pairs A-U, G-C A, U (no T’s in RNA) RNA assists DNA in manufacturing needed proteins

RNA Structure

Practice On your paper, complete the missing DNA strand by adding the complementary bases. A T C G T T G C C A T C T A G C A A C G G T A G Make the complementary RNA strand for the single strand of DNA below: A A T C A T C A C G T T U U A G U A G U G C A A

Step 1: Transcription Copying the portion of DNA that carries the code for a protein is called transcription. A portion of DNA that codes for a specific protein is unwound RNA nucleotides find their compliment DNA - ATTGCTCCG RNA - UAACGAGGC The RNA strand (mRNA) releases from the DNA strand mRNA strand is edited and released from the nucleus

Step 2: Translation Translation is the process of interpreting mRNA to build a chain of amino acids that make up a protein mRNA leaves the nucleus and heads to the ribosomes where translation will occur Each sequence of three nucleotides is called a codon. Each codon codes for a specific amino acid. UAA CGA GGC codon codon codon

tRNA anticodons – AUU GCU CCG Translation Steps Amino acids are brought to the ribosome by tRNA There are 20 different tRNA molecules, one for each type of amino acid tRNA anticodons find their compliment codon on the mRNA mRNA codons – UAA CGA GGC tRNA anticodons – AUU GCU CCG 4. Peptide bonds forms between the amino acids forming a polypeptide 5. Translation stops when a stop codon is reached tRNA

Protein Synthesis https://www.youtube.com/watch?v=gG7uCskUOrA&nohtml5=False

Genetic Code The nearly universal genetic code identifies the specific amino acids coded for by each three-nucleotide mRNA codon. The Human Genome: The entire gene sequence of the human genome, the complete genetic content, is now known. Approximately 30,000 genes.

Roles of RNA in Translation All three major forms of RNA—mRNA, tRNA, and rRNA—are involved in the process of translation. Remind students that all three major forms of RNA are involved in the process of translation. Click to reveal messenger RNA. Tell students: The mRNA molecule carries the coded message that directs the process of translation. Click to reveal transfer RNA. Tell students: The tRNA molecules deliver the amino acids, enabling the ribosome to translate the mRNA’s message into protein form. Click to reveal ribosomal RNA. Tell students: The ribosomal RNA molecules hold ribosomal proteins in place and may even carry out the chemical reaction that joins amino acids together. Point out to students that these components, which translate the genetic code for the purpose of synthesizing new protein molecules, are common to all organisms.

All that DNA does!! 1. Replication – copies DNA to make another identical double strand of DNA 2. Transcription – makes a copy of a section of DNA and creates a single strand of mRNA 3. Translation – reads the sequence of mRNA nucleotides to build a protein

After Protein is made: Protein Secretion The polypeptide ER for any further structural components Golgi bodies package the protein and send it to the cell membrane The protein is then secreted from the cell and sent where the body needs it http://courses.washington.edu/conj/cell/secretion.htm

Gene Expression When a gene (segment) of DNA code is used to build a protein, scientists say that gene has been expressed. Have students consider the illustration of gene expression in this slide―the way in which DNA, RNA, and proteins are involved in putting genetic information into action in living cells. Point out to students that this illustration is a simplification and have them review the other figures used in this presentation if they are confused on that point. Tell students: The protein made at the end of transcription and translation is the ultimate use or expression of the code in the DNA segment used in transcription. Scientists will say that region of DNA has been expressed. This means its code was used to build a protein. Summarize gene expression in the following manner: DNA carries information for specifying the traits of an organism. The cell uses the sequence of bases in DNA as a template for making mRNA. The codons of mRNA specify the sequence of amino acids in a protein. Proteins, in turn, play a key role in producing an organism’s traits. Explain that many RNA molecules are not translated into proteins but still play important roles in gene expression. Relate the diagram to the central dogma of molecular biology. Ask a volunteer to point out the DNA in the illustration. Click to highlight the DNA. Ask a volunteer to point out the RNA in the illustration. Click to highlight the RNA. Then, ask a volunteer to point out the protein in the illustration. Click to highlight the protein. Share with students that one of the most interesting discoveries of molecular biology is the near-universal nature of the genetic code. Although some organisms show slight variations in the amino acids assigned to particular codons, the code is always read three bases at a time and in the same direction. Despite their enormous diversity in form and function, living organisms display remarkable unity at life’s most basic level, the molecular biology of the gene.

Mutations If the mRNA does not copy the code correctly, the amino acid chain will be altered – this is called a mutation

Gene Mutations Point Mutations – changes in one or a few nucleotides Substitution THE FAT CAT ATE THE RAT THE FAT HAT ATE THE RAT Insertion THE FAT CAT XLW ATE THE RAT Deletion THE FAT ATE THE RAT

Gene Mutations Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function. Insertion THE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA T Deletion TEF ATC ATA TET GER AT H H

Significance of Mutations Most are neutral Eye color Birth marks Some are harmful Sickle Cell Anemia Down Syndrome Some are beneficial Sickle Cell Anemia to Malaria Immunity to HIV Image: examples of different eye color (Reddit)

What Causes Mutations? There are two ways in which DNA can become mutated: Mutations can be inherited. Parent to child Mutations can be acquired. Environmental damage Mistakes when DNA is copied

Chromosome Mutations Down Syndrome Chromosome 21 does not separate correctly. They have 47 chromosomes in stead of 46. Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.

Chromosome Mutations Cri-du-chat Deletion of material on 5th chromosome Characterized by the cat-like cry made by cri-du-chat babies Varied levels of metal handicaps

Extra Video https://highered.mheducation.com/sites/9834092339/student_view0/chapter15/protein_synthesis.html