And this is going to be the next codon. In theory only 22 codes are required: one for each of the 20 naturally occurring amino acids, with the addition of a start codon and a stop codon to indicate the beginning and end of a protein sequence. Instead, transcription is controlled individually for each gene or, in bacteria, for small groups of genes that are transcribed together. Proteins are made up of sequences of amino acids. And of course it'll keep going on and on and on.
Let me write that down. It is a complex process, particularly in eukaryotes, involving an array of enzymes. She graduated from the University of California, Santa Barbara, with a B. So you have 64 possible codons that need to code for 20 amino acids. It occurs in the cytoplasm either on free ribosomes or on the rough endoplasmic reticulum. The enzyme makes the complementary strand by finding the correct base through complementary base pairing, and bonding it onto the original strand.
I wanted the other side. Thymine pairs with adenine, so thymine, adenine. Researchers found experimentally that the genetic code is written in a language of three bases. And then cytosine pairs with guanine. The basic technique in gene transfer is outlined below.
These plasmids can be removed and cleaved by restriction enzymes at target sequences. Chargoff's rule states that A always bonds to T with double bonds and G always bonds to C with triple bonds. Now let's see, I have it is U A C, so it's gonna be U A C then U U then A C G okay? So this is overkill and allows codons to be used for other purposes as well. Although the resultant protein will have one incorrect amino acid it stands a high probability of being functional. Some of these modifications are shown in. U2 — Helicase unwinds the double helix and separates the two strands by breaking hydrogen bonds.
Now how does that happen? This is what's kind of doing the work of life. Thymine pairs with adenine Let me do that a little bit neater. Mutation Rates and Mutagens Mutations are normally very rare, which is why members of a species all look alike and can interbreed. These regions are called introns and make up around 95% of the genome. Actually let me write this down. So we have an adenine and thymine, adenine and thymine, adenine and thymine.
During most of the life of a cell the chromatin is dispersed throughout the nucleus and cannot be seen with a light microscope. And then let's copy and paste the other side. Or actually used to code for a certain type of protein. These kinds of mutation are called point or gene mutations because they affect specific points within a gene. Any set of three bases that determines the identity of one amino acid is called a triplet.
And then we have an A, let me make sure I change it to the right color. Figure 14: Ribosomal subunits Steps of Translation: 1. This happens in the nucleus by means of enzymatic complexes produced themselves by specific genes. And so now that thing can leave the nucleus, go attach to a ribosome, and we'll talk more about that in future videos exactly how that's happened, and then this code can be used to actually code for proteins. Translation — Protein Synthesis 1.
A2 Production of human insulin in bacteria as an example of the universality of the genetic code allowing gene transfer between species A. Basic technique used in gene transfer E. As a cell divides, the two new cells would want to have the same genetic material. T wo specific amino acids are now being held side by side. The bases therefore form base pairs, which are like rungs of a ladder.
And how many possible codons do you have? These are called complementary base pairs. As a result, each new cell has its own complete genome. These nucleotides are available to form complementary pairs with the single-stranded nucleotides of the unzipped molecule. Modifications are carried out by other enzymes and include: chain cutting, adding sugars to make glycoproteins or lipids to make lipoproteins. And we actually haven't drawn the next codon after that 'cause we need three bases to get to the next codon.
A free nucleotide locates on one opened strand at one end, and then a second nucleotide can join the first. Thymine is still going to pair with adenine, just like that. The built polypeptide chain is now ready to be folded into the destined protein. As you will recall, polypeptides are composed of amino acids covalently bonded together in a specific sequence. A well-known example is Down syndrome trisonomy 21 where there are three copies of chromosome 21 instead of the normal two. The activity of those lat genes yes or not in state of transcription is often determined by a confluence of external factors and internal cellular signals. So let's understand what a molecular basis of heredity would need to do.