 Hi everyone, welcome to basic science series. This is the third lecture of our biochemistry lecture series. In the previous lecture we discussed about the introduction of the genetics of protein synthesis and in this lecture we will be discussing about the H. Govind Kurana's experiments What are open reading frames start and stop codones in protein synthesis? Alright without delay. Let's start the lecture Previously we discussed about decoding the genetic code. What are the different experiments that were performed to decode the genetic code? First experiment was 1961, Nirenberg's and Mithai experiment and second one was 1964, Nirenberg's and Philippe Leider experiment. Both of these experiments were able to decode 54 codones out of 64, but there was an complementary approach that was adopted by professor Har-Govind Singh Kurana to decode the genetic code The complementary approach adopted by H. Govind Kurana included the production of 224 base-pale long RNA molecules. It is important to consider here that he was able to synthesize those molecules chemically. So chemical method was standardized to produce these molecules and when those molecules were expressed they were able to produce polypeptide chains that were one or few amino acid long in repeat Experimental results from H. Govind Kurana's experiment and from Nirenberg and colleagues' experiments were combined together and analyzed. After the analysis, it was found out that they were able to decode 61 codones out of 64, but still three codones were missing and the function was unknown. So three codones when they were incorporated in the sequence, it was found out they terminated the sequence so they were assigned as stop codones Decoding the genetic code was considered as the most important scientific discovery of all time because after that we were able to understand the language of life Let's talk about codones. Codones are used to translate the genetic information There is start codon and there are stop codones. Start codon initiates the translation It's also known as initiation codon and stop codon terminate the translation so they are also known as termination codon. The example of start codon is AUG The example for stop codon are UAA, UAG, UGA and they all terminate the protein synthesis and therefore they're also known as nonsense codones. I have a question to everyone that how the proteins were synthesized without knowing that there was initiation codon I mean they were trying to understand the function so they they were not aware about the UG is an initiation codon Then how the experiments were conducted? Please answer in comment section. All right. Let's talk about what is an open reading frame by definition 50 or more codon sequences without any termination codon is known as open reading frame and Long open reading frame is considered as genes and those genes are able to synthesize particular protein There are softwares that can analyze these open reading frames Approximately 60,000 Dalton protein will have an open reading frame of more than 500 codons Codons are degenerate. It means a single amino acid can be encoded by multiple codons In case of leucine There are six codon that can encode leucine and this particular property is not uniform for all amino acid for example Methionine and tyrosine they are encoded by a single codon Arginine leucine and serine they are encoded by six different codons The next important point is codons are nearly universal except few mitochondrial genes bacteria and single cell eukaryotes We all show same genetic code that means Whether it's E. Coli whether it's human tobacco plant frog or viruses we all have same genetic code that means we have common evolutionary ancestry and The genetic code is preserved throughout the generation All right, let's summarize the lecture in this lecture. We discussed about H. Covind Kuran as experiments What are open reading frames what we understand by a start and stop codons and we also discussed about some properties of genetic code We will continue the biochemistry series. I'll see you in the next video. Please subscribe the YouTube channel. Thank you and namaste