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Do all proteins start with methionine?

You are correct in thinking that since the translation of mRNA begins with AUG, which codes for methionine, then all proteins should contain a methionine at their N-terminus (aka start site). But, it ...
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12 votes
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Are codons that map to the same amino acids interchangeable?

I think given that you're just getting started with genetics, you can say that the codons are interchangeable. This is generally true, though not technically correct. Here are a few reasons for why ...
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11 votes

From which end of mRNA does transcription start?

They're both correct. The confusion stems from the book talking about the anticoding strand as well as the newly-formed coding RNA strand, whereas Khan Academy talks only about the coding strand. ...
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why does translation occur more frequently than transcription?

The simple answer Under the assumption that each mRNA molecule is translated at least once, by necessity translation will happen more often than transcription. This is because the only way to get a ...
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8 votes
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Stop codons and exons?

Take a look at this schematic of a mature mRNA. [source] The coding region (ie the part that is translated) is between the start and stop codons, but the 5' and 3' untranslated regions (UTRs) are ...
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8 votes
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Can ribosomes read ssDNA?

Summary Messenger RNAs that are recruited to the ribosome for protein synthesis in vivo, need to satisfy particular structural requirements and must interact with the protein initiation factors that ...
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How can a good SD / Kozak sequence enhance translation efficiency?

I would strongly recommend looking in more detail into available resources for SD and Kozak sequences, wikipedia basically answers these questions and has plenty of further reading if you desire to ...
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Why are there two replicase proteins translated from tobacco mosaic virus RNA?

Short Answer As of 2021 the rationale for the production of two proteins from the Tobacco Mosaic Virus (TMV) replicase gene is incompletely understood. The two proteins share some activities but not ...
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7 votes
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Mutation That Loses Stop Codon

No, this will not happen. mRNAs are inspected in the nucleus before they are exported into the cytoplasm (at least in eukaryotes), where transcription and translation don't happen at the same place. ...
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7 votes
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Effect of a doubling of the start codon in a gene

There is a basic misconception in the question you have asked, which @biogirl has explained. There is only one start Codon in any mRNA and it defines the open reading frame. All other AUGs in the ...
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Do two compatible tRNA codons bond together?

Yes, tRNA can form dimers. For example it was shown that E. Coli tRNA GCC forms homodimers, i.e. two identical molecules interact with each other. In this case the dimerization occurs between the anti-...
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Is the start codon regarded as part of the UTR (untranslated region)?

Because the start codon is translated into methionine, it clearly can not be part of the 5'-untranslated region, as @Johnny writes in his answer. The more contentious question would be for the stop ...
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Do all proteins start with methionine?

When ribosomes create peptides, Methionine is the starting amino acid. But, in many proteins, Methionine Aminopeptidases cut it off from N-terminus. This happens in cases when methionine is not ...
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How do aminoacyl-tRNA synthases distinguish between similar amino acids?

Aminoacyl-tRNA sythetases are highly specific to their corresponding amino acid. First, the activation site, where the amino acid binds, constitutes a complex network of intermolecular interactions. ...
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From which end of mRNA does transcription start?

@Thymine's answer is correct. I just thought I'd post a more graphic answer for clarity. ...
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How can I tell if regulation is at the transcriptional or translational level?

From the Methods section: Human TfR in plasmid cDNA was a gift from Tim McGraw (Weill-Cornell Medical College, New York, NY). Human TfR cDNA was subcloned in frame with EGFP in the Clontech ...
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Why is the DNA codon table "equal" to the RNA codon table

Genetic code and codons are always used with reference to RNA. When talking about DNA, the the sense strand of a gene is considered its sequence. The anti-sense strand though is the template for mRNA ...
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How does aminoacyl-tRNA synthetase recognize different tRNAs?

You give the answer in your question: binding areas that recognize a particular tRNA through unique identity sites at the acceptor stem and/or anticodon loop of the tRNA. The point is that ...
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How to determine the most likely reading frame of a DNA sequence?

This is what we classify as a homework question, but as it satisfies the criterion of the poster demonstrating an attempt to answer it, I provide the following suggestion of an answer. I assume that ...
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How to memorize Transcription and Translation?

I prefer a conceptual distinction rather than a mnemonic in this case. I've always thought of a transcript as an exact copy of record - that's the meaning of the word in English, and an RNA transcript ...
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Can human mRNA be translated in vitro by prokaryotes?

Short answer: Yes, you can. Usually these are coupled systems for transcription and translation. For these you clone the gene of interest into a vector which contains a prokaryotic promoter which is ...
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Are codons that map to the same amino acids interchangeable?

A good answer is already provided by @canadianer, but as with many things in biology it is important to keep in mind what organism and/or cell type we are talking about. Because the nuances of the ...
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Stop codons and exons?

You mix up translation and transcription. Transcription creates mRNA from DNA template. Transcription also includes splicing, that is excision of introns so that mature mRNA contains only exons. In ...
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Redundancy of the genetic code

Wobble pairing is just a phenomenon and not a hard and fast rule. There are some justifications for why it should exist and that is why it is still called a hypothesis. And this statement is not true:"...
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dsDNA translation

There are a few confusions here, I will try to get them resolved without adding more: First, a gene is always read in the 5' -> 3' direction, no matter on what strand of the double helix is is ...
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Effect of a doubling of the start codon in a gene

AUG functions as a start codon only when it is at the 1st position of the open reading frame. Whenever AUG is present in between, it codes for methionine amino acid. Go through the basics of ...
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How much nucleoside triphosphate is required to form one peptide bond during protein synthesis?

Although the question shows considerable effort to achieve clarity, the way it is phrased as: How many molecules of nucleoside triphosphate… [does] it take to release enough energy still allows ...
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Can mRNA be used by ribosomes more than once?

There are a few cases in translation that I can think of where an mRNA is translated more than once: the closed loop model of mRNA translation, translation reinitiation, and translation by polysomes. ...
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Why is an initiator tRNA required, distinct from the methionine tRNA used in elongation?

I think the key to understanding this is to appreciate how different the initiation process is from the rest of translation. The 30S ribosomal subunit recognises start codons via an interaction with ...
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How to find the amino acid in the DNA protein

Then you just have to read the codon until you reach a stop codon. There are three stop codon UAA, UGA and ...
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