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Biology Chapter 17
From Gene to Protein
| Term | Definition |
|---|---|
| Direction of Genetic Flow | DNA ---> RNA ---> Protein... DNA(Blueprint, Genes) ---(Transcription)---> RNA(Working Copy) ----(Translation)--->Protein(Consist of Amino Acids) |
| Gene Expression | Coding for a product. Process by which DNA directs the synthesis of proteins. Proteins connect the genotype to the phenotype |
| Protein Synthesis Event | Two steps... 1. Transcription(rewrite).. 2. Translation(decoding) |
| Types of RNA | Three major kinds... 1. Messenger RNA(mRNA).. 2. Transfer RNA(tRNA).. 3. Ribosomal RNA(rRNA) |
| Messenger RNA(mRNA) | Produced by Transcription. Represents DNA as a "rewrite, working copy". Will be translated by tRNA. Will be decoded in groups of 3 bases(triplet code) called a Codon. |
| Codon | 3 bases. Triplet code. EX: AUG/UUU/CAC |
| Transfer RNA(tRNA) | The "decoder, translator". Has an amino acid binding site and carries it to the site of protein synthesis(ribosome) for assembly. Will translate the mRNA codons by matching its anticodon in base pairing. This process is called Translation. |
| Anticodon | Will translate the codon with a group of 3 bases that match the codon in complementary base pairs. EX: UAC/AAA/GUG |
| Ribosomal RNA(rRNA) | Most abundant RNA. Major component of ribosomes. Makes up approximately half of the ribosomal structure |
| Ribosome Structure | Made of enzymatic rRNA and protein. Ribozyme. Consists of a Large subunit(has binding sites) and Small subunit(platform) and three tRNA binding sites in this order from right to left... 1. Amino Site(A).. 2. Peptide Site(P).. 3. Exit Site(E) |
| Genetic Code - Universal Code for All Lifeforms | Based on the triplet code. Each of the 64 triplet codons corresponds to a specific amino acid or a start of stop signal. Look for wobbles. |
| Wobbles | Flexible third position bases in the codon. Redundancy is built in. So even when mutation occurs, sometimes code still follows same amino acid sequence |
| Protein Synthesis | DNA ---> mRNA ---> Protein |
| Transcription | DNA(gene) -----> mRNA. Conversion of genetic information from DNA nucleotides to RNA nucleotides. Occurs in nucleus. Three steps... 1. Initiation.. 2. Elongation.. 3. Termination |
| Promoter Region(start) | The DNA sequence where RNA polymerase attaches and initiates transciption |
| Coding Region | The DNA sequence that is transcribed and will code for a polypeptide |
| Terminator Region | The DNA sequence that signals the end of transcription |
| cDNA | Nontemplate strand in DNA replication. 5'-->3'. Is called cDNA for complementary DNA |
| tDNA | Template strand in DNA replication. 3'-->5'. Is called tDNA for template DNA |
| RNA Polymerase | Pries the two DNA strands apart and joins together RNA nucleotides complementary to the DNA template strand and assembles mRNA Can only assemble the mRNA molecule in the 5'--->3' direction. Does not require a primer to start from |
| Initiation | RNA polymerase binds to the promoter region of the DNA sequence with the aid of various transcription factors(proteins) |
| Elongation | RNA polymerase moves along the template strand assembling RNA nucleotides, unwinding the helix as it travels. The DNA double helix will reform after the assembly has passed |
| Termination | The RNA polymerase transcribes a termination sequence that allows for the mRNA to be released from the RNA polymerase |
| mRNA Processing | Preparing the pre-mRNA for the next phase. Occurs in the nucleus. Two steps... 1. Modification of the ends of the mRNA.. 2. RNA Splicing |
| Modification of the Ends of the mRNA | 1. Adds a poly-A tail at the 3' end. (50-250 AAAAAAA, etc.).. 2. Adds a GTP cap to the 5' end which will catalyze next event(translation) |
| RNA Splicing | Introns are cut out and exons are joined together |
| Introns | (Intervening sequences) noncoding segments that lie between coding regions. They are cut out of the mRNA molecule |
| Exons | Coding regions. These are connected together once the introns are cut out. Then they exit the nucleus through the nuclear pores |
| Product of Transcription | A mRNA 5'----->3' sequence that can be translated. It will exit the nucleus and move out to the ribosomes |
| Translation | mRNA----->polypeptide(protein primary level). Conversion of the genetic information language of RNA to the language of Proteins(from nucleotides to amino acids). Three steps... 1. Initiation.. 2. Elongation.. 3. Termination |
| Primary Level of a Protein | Sequence of amino acids held together by peptide bonds. This sequence is determined by the sequence of nucleotides in a gene(DNA) |
| 1. Intiation Process | 1. mRNA exits the nucleus and enters the cytoplasm.. 2. mRNA will attach to the small subunit of the ribosome with help from the GTP cap, and the first codon lines up in the P site position and the second codon lines up in the A site position. |
| 2. Initiation Process | 3. The first codon is AUG. This a start or initiation codon which will match up to a tRNA which will carry the amino acid methionine(met) |
| 3. Initiation Process | 4. tRNA will carry the correct amino acid to the P site position and decode the mRNA by paring its anitcodon with mRNA's codons. The large subunit of the ribosome connects to the small ribosome subunit |
| 1. Elongation Process | 1. A second tRNA will carry the second amino acid to the A site.. 2. Peptide bonds will form between the amino acids in the P and A site of the ribosome.. |
| 2. Elongation Process | 3. The tRNAs shift on position over and the process repeats until a terminator codon is present. The tRNA exit out the E site and the growing polypeptide(protein) exits out of the Exit Tunnel |
| 1. Termination Process | A terminator codon enters the A site, signaling a release factor. The ribosome's subunits separate and release the mRNA molecule that it was translating |
| Polyribosomes | Strings of ribosomes that can translate a single mRNA strand simultaneously, allowing multiple copies of the protein to be produced quickly |
| Point Mutation | A mutation in which there is a change in just 1 base pair. Three types.. 1. Silent Mutation.. 2. Missence Mutation.. 3. Nonsense Mutation |
| Silent Mutation | The codon still codes for the same amino acid due to a wobble. EX: UGU--->UGC still codes for Cysteine |
| Missense Mutation | The codon codes for a different amino acid. EX: UGU--->UGG will code of for Tryptophan instead |
| Nonsense Mutation | The codon does not code for an amino acid, but becomes a terminator codon. Premature termination. EX: UGU--->UGA signals a release factor and not an amino acid |
| Frameshift Mutation | Due to insertion(addition) or deletion(removal) of nucleotide. The reading frame of the mRNA is shifted over one position. A completely different amino acid chain is assembled or will prematurely terminate synthesis because terminator codon could appear |
Created by:
TimBiology1
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