PROTEIN SYNTHESIS: (chapter 10/11)

25 July 2022
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question
Explain what is meant by the concept "one gene - one polypeptide".
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The idea, since shown to be an oversimplification, that each gene in the genome encodes only a single polypeptide - that there is a one-to-one correspondence between genes and polypeptides.
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Indicate the similarities and differences between DNA and RNA.
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DNA is double stranded, it carries the coded genetic information for making proteins, the code is in four bases, argenine, cytosine, guanine and thymine. RNA is single stranded molecule that copies the code from the DNA and carries it to the ribosomes to make new proteins. It has the same bases except that thymine is replace by uracil. And of course the sugar in DNA is deoxy ribose whereas RNA is just ribose.
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Describe and explain what is meant by transcription
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The synthesis of RNA using one strand of DNA as a template. DNA transcription is a process that involves transcribing genetic information from DNA to RNA. The transcribed DNA message, or RNA transcript, is used to produce proteins.There are three main steps to the process of DNA transcription. •RNA Polymerase Binds to DNA: • DNA is transcribed by an enzyme called RNA polymerase. • Elongation •Termination
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Describe and explain what is meant by translation.
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The synthesis of a protein (polypeptide). Takes place on ribosomes, using the information encoded in messenger RNA. Protein synthesis is accomplished through a process called translation. After DNA is transcribed into a messenger RNA (mRNA) molecule during transcription, the mRNA must be translated to produce a protein. In translation, mRNA along with transfer RNA (tRNA) and ribosomes work together to produce proteins.
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Indicate where and how transcription occurs in eukaryotic cells.
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In a prokaryotic cell, transcription and translation are coupled; that is, translation begins while the mRNA is still being synthesized. In a eukaryotic cell, transcription occurs in the nucleus, and translation occurs in the cytoplasm. Transcription and translation are spatially and temporally separated in eukaryotic cells; that is, transcription occurs in the nucleus to produce a pre-mRNA molecule. The pre-mRNA is typically processed to produce the mature mRNA, which exits the nucleus and is translated in the cytoplasm.
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Indicate where and how translation occurs in eukaryotic cells.
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In a eukaryotic cell, translation occurs in the ribosomes that are in the cell cytoplasm and the endoplasmic reticulum. Translation is the process where the codons of the mRNA are decoded. The codons are translated to the language of amino acids from the language of nucleic acids.
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Given a DNA sequence and a genetic codon dictionary, indicate the mRNA sequence.
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A = U T = A C = G
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Given a DNA sequence and a genetic codon dictionary, indicate the tRNA anticodons.
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Replace your As with Us, your Us with As, your Cs with Gs, and your Gs with Cs.
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The sequence of amino acids in the polypeptide that is formed.
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Assuming that this sequence is from 5' to 3' (this is the direction mRNA is translated), the amino acid sequence from n-terminus to c-terminus would be as follows: Leucine - Phenylalanine - Arginine - Cysteine. This is because the five codons here correspond to the following. (The last codons signals for peptide synthesis to stop, and does not correspond to an amino acid.) CUG Leucine; UUC Phenylalanine; AGG Arginine; UGU Cysteine UAG (stop)
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Know the start and stop codons for translation.
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START - AUG STOP - UAA, UAG, or UGA
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Identify concept of introns.
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Portion of a of a gene within the coding region that is transcribed into pre mRNA but is spliced out prior to translation. (Contrast with exon).
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Identify concept of exons.
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A portion of a DNA molecule, in eukaryotes, that codes for part of a polypeptide. (Contrast with intron).
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Identify concept of introns and exons.
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In most eukaryotic genes, coding regions (exons) are interrupted by noncoding regions (introns). During transcription, the entire gene is copied into a pre-mRNA, which includes exons and introns. During the process of RNA splicing, introns are removed and exons joined to form a contiguous coding sequence. This "mature" mRNA is ready for translation.
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Somatic mutation
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Permanent genetic change in a somatic cell. These mutations affect the individual only; they are not passed on to offspring. (Contrast with germ line mutation.)
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Germ line mutation
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Mutation in a cell that produces gametes (i.e., a germ line cell). (Contrast with somatic mutation.)
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Loss of function mutation
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A mutation that results in the loss of a functional protein. (Contrast with gain of function mutation.)
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Gain of function mutation
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A mutation that results in a protein with a new function. (Contrast with loss of function mutation.)
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Conditional mutation
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A mutation that results in a characteristic phenotype only under certain environmental conditions.
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Point of mutation
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A mutation that results from the gain, loss, or substitution of a single nucleotide.
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Chromosomal mutation
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Loss of or changes in position/direction of a DNA segment on a chromosome.