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Current time:0:00Total duration:4:50

Evidence that DNA is genetic material 1

Video transcript

one criterion that we use to define biological life is that the organism must have the ability to reproduce and the parent organism must have the ability to pass on to its offspring some sort of material that contains the instructions for living and we call this material genetic material what is genetic material well today we know that it's DNA or deoxyribonucleic acid but this wasn't always so obvious we're going to go through a couple of earlier experiments that help prove to us that DNA genetic material the first experiment we're going to discuss was one that was conducted by a scientist by the name of Friedrich Miescher and Miescher lived from 1844 to 1895 and we sure worked with cells that he took out of pus until we know that these are lymphocytes and lymphocytes happen to have very large nuclei so that's the cell the nucleus might look something like that and of course there is this material inside the nucleus and because the nuclear so large Misha was able to isolate the material inside the nucleus and he analyzed this material and came to the conclusion that it was made up of two components the first was protein and the second was this substance that acted like an acid and so he called it nucleic acid nucleic because it came from the nucleus and so Miescher was the first one to isolate and identify nucleic acid the next experiment we're going to talk about was one conducted by scientists who lived at about the same time his name was Wilhelm Roux and he lived from 1850 to 1924 Andrew worked with cells that were dividing and he analyzed these cells so I drew cell here and I drew a couple of organelles also let's just label them we have the endoplasmic reticulum here we have a couple of mitochondria and singular it's mitochondrion and then we have a couple of ribosomes I'm just going to abbreviate it like that and I also drew some vesicles and of course in the center we have the nucleus and we're going to see that this cell is undergoing mitosis right now so I'm going to draw the chromosomes like that in the center I'm going to draw four chromosomes and I'm also going to draw the mitotic spindle which will help to separate the chromosomes into the two cells that will um that are being formed and what Roux noticed was that when the cell divided so the organelles were not necessarily distributed in a very organized and even fashion you can see the cell on the Left got three mitochondria the cell there I only got two cell on the left got three ribosomes the one of the right only got two but he noticed that the material in the nucleus divided in an extremely organized fashion so each nucleus guy exactly four chromosomes and so Roux concluded that because the material in the nucleus was divided in a very orderly and even fashion that that must be the genetic material and this makes sense because the genetic material or instructions for a living is the most important thing that the parent cell has to pass on to the daughter cell if one of the daughter cells didn't get enough mitochondria well that's also terrible as long as it has the correct instructions for a living it can make more mitochondria if one of the cells accidentally didn't get a ribosome well if it has the right instructions for living it can make ribosomes so the conclusion here was that genetic material is made up of protein and or nucleic acid this was the conclusion that Friedrich Miescher experiment Andrews experiment helped prove