CHAPTER 12 - Ch 12 One Gene One Polypeptide Gene is a DNA...

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Ch. 12- One Gene/ One Polypeptide Gene- is a DNA sequence Experiment: If you alter a gene, you will also alter the phenotype. Ex). Breadmold- easy to look at, haploid form- easy to see phenotypic change. Wild type: grew on minimal nutrients (medium/media) everything essential for life. Phototroph- any wild type. Took mold and exposed to mutagen- anything that causes a mutation, then took the molds and put in minimal media. (Many could not grow, they needed something added to grow). The mutation they look at arg-(amino acid) took mutant add arg to medium, they can now grow! Noticed not all the arg mutants had the same genotype, so there were multiple mutations that cause you to have an arg mutant. There are metabolic pathways, and multiple enzymes involved for producing the arginine. They figured out each gene is specific to a particular enzyme. (Figure 12.1) Theory: after the experiment one gene produces one enzyme. Some enzymes are made of multiple poly-peptide chains. Gene can code for an RNA molecule that is not made into a poly-peptide (or protein). Some genes are expressed, and made to control the expression of other genes. DNA never leaves the nucleus! Steps producing protein from DNA: Start with DNA turn into RNA, which you then turn into protein! DNA RNA (Transcription) RNA Protein (Translation in the cytosol)
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Transcription: DNA will be made into single-stranded RNA, this happens in the nucleus. The RNA will leave the nucleus through the nuclear pores. Its now in the cytosol then have translation occur RNA converting into protein. RNA: RNA generally single-stranded Sugar for RNA is ribose Slight change in bases, C,G,U,A (no T-specific to DNA) 3 types (you will see in eukaryotic cell): mRNA: known as messenger RNA, made during transcription, copying info & carrying info out of the nucleus. tRNA: transfer RNA, used during translation (RNA-protein), tRNA specifies amino acid sequence of the protein (double-stranded, folds upon itself, clover shape). rRNA: ribosomal RNA, extremely important, stays in the nucleus, encodes protein needed to make ribosomes. Some virus’: non-living can use RNA. Polio & Flu RNA acts as their genetic info. Anything living has DNA for genetic info. HIV virus-retro virus- RNA is its genetic material, this virus infects a host cell-it takes RNA and converts it to DNA. (Reverse transcriptase: DNA DNA).
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Transcription process DNA RNA process: need DNA template need ribonucleoside triphosphates need special enzyme, RNA polymerase (makes the RNA) 3 steps of transcription: Overview: 1 strand of DNA will be unwound and used to make RNA, when the DNA unwinds, it only partially unwinds (just the region you need) form rRNA (transcript), once it’s formed it will peel away from DNA and rewind.
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