Lyrapettigrew
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Hello, does anyone know two reasons why some of the bases in a gene do not code for amino acids?

I am not entirely sure and struggling a little, however, I do know that more than 98% of the DNA in a cell does not code for the amino acid sequences of proteins. Therefore, I thought that perhaps;

1. One reason may be introns whose information is ignored during protein synthesis. These are DNA base sequences within genes that do not code for the amino acid sequence of a polypeptide.

2. The second reason I thought may be stop codons, which are nucleotide triplets within mRNA that signal the termination of translation into proteins.

I do not think that I am correct and would appreciate any advice or suggestions ✌️
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harleyh4
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Your first reason is correct; during protein synthesis, proteins aren’t synthesised from the DNA directly, instead mRNA is made using the DNA as a template (called transcription). Introns are removed from the mRNA (splicing) and then this molecule with only exons is used to synthesise proteins (translation). Hence these introns do not code for amino acids.

Stop codons don’t really amount to much in DNA so this isn’t a major contributor to that 98%, which is why I think the big one is introns (e.g. turned off genes).

Another factor to consider transcriptional factors, which can stop the transcription of DNA, so those bases don’t code for amino acids. I don’t really know enough about transcriptional factors to say how much of an impact it would have though so take this last paragraph lightly haha.
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Lyrapettigrew
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(Original post by harleyh4)
Your first reason is correct; during protein synthesis, proteins aren’t synthesised from the DNA directly, instead mRNA is made using the DNA as a template (called transcription). Introns are removed from the mRNA (splicing) and then this molecule with only exons is used to synthesise proteins (translation). Hence these introns do not code for amino acids.

Stop codons don’t really amount to much in DNA so this isn’t a major contributor to that 98%, which is why I think the big one is introns (e.g. turned off genes).

Another factor to consider transcriptional factors, which can stop the transcription of DNA, so those bases don’t code for amino acids. I don’t really know enough about transcriptional factors to say how much of an impact it would have though so take this last paragraph lightly haha.
Thank you very much for your reply, you have helped tremendously. I will research transcriptional factors now, I think that you have set me down the right path! 😁
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harleyh4
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(Original post by Lyrapettigrew)
Thank you very much for your reply, you have helped tremendously. I will research transcriptional factors now, I think that you have set me down the right path! 😁
You’re welcome! I really hope it helps 😅
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Lyrapettigrew
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(Original post by harleyh4)
You’re welcome! I really hope it helps 😅
I looked in transcription factors, and found that they are proteins which regulate the transcription of genetic information from DNA to mRNA by binding to a DNA sequence at the point called the promoter. Their purpose is to regulate, that is turn on and off, genes to ensure they are expressed at the optimal times and in the correct cell, i.e. for growth, cell migration, cell division.
Such factors can promote or repress active transcription to make it easier/harder for RNA polymerase to catalyse the formation of phosphodiester bonds between RNA nucleotides to form a mRNA molecule during transcription. Therefore, the fact that they can repress RNA polymerase, making it so they can't bind to the promoter or begin transcription means that the entire process of protein synthesis, and thus the production of new amino acids is void and hopeless.

Do you think this would sufficiently answer the question? Or do you think the answer should be more specific as to why the bases in a gene do not code for amino acids?
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