crash course why 3 letter codons

What is the sequence above the transcription unit?

Now each transcription unit has a sequence just above it on the strand and that's called 'upstream', biologists call that 'upstream' on the strand, and that sequence sort of defines when the transcription unit is going to begin.

What is the end of a tRNA?

On one end of the tRNA is an amino acid. On the other end is a specific sequence of three nitrogenous bases. These two ends are kind of matched to each other. Each of the 20 amino acids that we have in our body has its own sequence at the end. So if the tRNA has the amino acid methionine on end end, for instance, it can have UAC as the nucleotide sequence on the other end.#N#( 8:59) Now, it's just like building a puzzle. The mRNA slides through the ribosome. The ribosome reads the mRNA three letters at a time - each set called a triplet codon. The ribosome then finds the matching piece of the puzzle: a tRNA with three bases that will pair with the codon sequence. That end of the tRNA, by the way, is called the anticodon. Sorry for all the terminology. YOU NEED TO KNOW IT!#N#( 9:19) And of course, by bringing in the matching tRNA, the ribosome is also bringing in whatever amino acid is on that tRNA. Okay so, starting at the 5' end of the mRNA that's fed into the ribosome, after the 5' cap, for almost every gene, you find the nucleotide sequence AUG on the mRNA. The ribosome finds a tRNA with the anticodon UAC, and on the other end of that tRNA is methionine. The mRNA, like a mile-long dollar bill, keeps sliding into that ribosome so that the next codon can be read, and another tRNA molecule with the right anticodon binds on.#N#( 9:51) If the codon is UUA, then the matching tRNA has an AAU on one end and a leucine on the other. And if the mRNA has an AGA, then the matching tRNA has a UCU on one end and an arginine on the other. In each case that new amino acid gets connected on to the previous amino acid - starting a polypeptide chain. Which is the beginning, the very beginning, of a protein.#N#( 10:12 ) But it turns out that here are LOTS of different ways to read this code. Because UUA is not only the triplet that codes for leucine, UUG does too! And arginine is coded for by six different triplets! This is actually a good thing. It means that we can make a few errors in copying and transcribing and translating DNA, and we won't necessarily change the end product. This process continues, with the mRNA sliding in a bit more, and the ribosome bringing in another tRNA with another amino acid, that amino acid binding to the existing chain and on and on and on and on, sometimes for THOUSANDS of amino acids to make a single polypeptide chain, for example.#N#( 10:42) This whole word is basically just the names of the amino acids in the sequence in the order in which they occur in the protein all 34, 350 of them.

How to make a hot pocket?

1. Break into the lair of the hot pocket company holding the secret manual. 2. Read the instructions on how to make the machinery to produce the hot pocket and the proportions of the ingredients. 3. Quickly write down that information in shorthand before I get caught by the hot pocket police. 4.

Which direction does DNA run?

Now, you'll remember from our episode about DNA structure that DNA strands run in one of two directions depending on which end of the strand is free and which end has a phosphate bond. One direction is 5'-3' and the other direction is 3'-5'.

What happens to RNA polymerase as it moves?

As it moves, the RNA polymerase re-zips the DNA behind it and lets our new strand of messenger RNA peel away. Eventually, the RNA polymerase reaches another sequence downstream, called a termination signal, that triggers it to pull off.

How does mRNA work?

The mRNA slides through the ribosome. The ribosome reads the mRNA three letters at a time - each set called a triplet codon. The ribosome then finds the matching piece of the puzzle: a tRNA with three bases that will pair with the codon sequence. That end of the tRNA, by the way, is called the anticodon.

What is the sequence of amino acids in a polypeptide called?

Now, the actual sequence of amino acids in a polypeptide - what you see scrolling along down there - is called its primary structure. One amino acid covalently bonded to another, and that one to another, in a single file.

How does mRNA work?

These messages – the mRNA – are transported out to the main part of the cell. Once the mRNA arrives, the cell can produce particular proteins from these instructions. The double-stranded DNA sequence is transcribed into an mRNA code so the instructions can be translated into proteins.

Where does messenger RNA come from?

Messenger RNA carries genetic information from DNA in the highly protected nucleus out to the rest of the cell, where structures called ribosomes can build proteins according to the DNA blueprint. (ttsz/iStock via Getty Images Plus) DNA is found inside the cells of every living thing.

Why is mRNA important?

As the intermediary messenger, mRNA is an important safety mechanism in the cell. It prevents invaders from hijacking the cellular machinery to produce foreign proteins because any RNA outside of the cell is instantaneously targeted for destruction by enzymes called RNases.

What is the difference between DNA and RNA?

Both RNA and DNA structures have a backbone made of sugar and phosphate molecules, but RNA’s sugar is ribose and DNA’s is deoxyribose. DNA’s sugar contains one less oxygen atom and this difference is reflected in their names: DNA is the nickname for deoxyribonucleic acid, RNA is ribonucleic acid.

Where is mRNA found?

It evolved billions of years ago and is naturally found in every cell in your body. Scientists think RNA originated in the earliest life forms, even before DNA existed. Here’s a crash course in just what mRNA is and the important job it does.

What is the function of mRNA?

It’s mRNA’s job to help fire up the cellular machinery to build the proteins, as encoded by the DNA, that are appropriate for that time and place . The process that converts DNA to mRNA to protein is the foundation for how the cell functions.

Where is DNA found in a cell?

DNA is found inside the cells of every living thing. It’s protected in a part of the cell called the nucleus. The genes are the details in the DNA blueprint for all the physical characteristics that make you uniquely you. But the information from your genes has to get from the DNA in the nucleus out to the main part of the cell – ...

Could DNA have a form of primitive "password protection"?

This question is inspired by a recent post about Covid RNA and why it had a polyA tail (a long sequence of As) at the end. The answers explained that this was a way of tracking the health of the RNA and that it was required for the proteins to be expressed.

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