hello today we're going to be talking about evolution the core theme of biology the three greatest unifying ideas in science all depend on the characteristics that we use to define life these unifying ideas are the cell theory all living things are made up of cells and cells arise from cells the chromosome theory of inheritance the principle that genes are located on chromosomes and that patterns of inheritance are determined by the behavior of chromosomes during meiosis and the theory of evolution characteristics of species can be modified from generation to generation and that species are related by common ancestry changes over time in a population as mentioned in the previous lecture recording a chromosome consists of a molecule of dna and dna is the hereditary material genes consist of specific segments of dna that code for proteins or products in the cell in the previous lecture recording you were to look up how many chromosomes are in each cell if you have not done that yet this would be a good time to pause the recording and make sure that you look this information up in eukaryotic cells the dna is found within the membrane bound nucleus in prokaryotic cells the dna is in a region called the nucleoid as it does not have a membrane bound nucleus this should be one of the differences that you have noted in your chart that you made for differences between eukaryotic and prokaryotic cells remember that we referred to genes as the recipe in our dna cookbook and genes are responsible for controlling all activities of a cell genes determine your physical appearance as well as your physiology which is how things work in your notebooks in large letters i want you to write the central dogma of biology and under the central dogma of biology i want you to write dna with an arrow pointing to the right rna with an arrow pointed to the right and protein and we'll come back to that dna is a double stranded helix and a helix is just kind of like a coil sort of like the old-fashioned telephone cords and this double helix this structure of dna was discovered by james watson and francis crick in 1953. this is a really interesting story there are several books written about it the double helix is one that's from one of the perspectives uh from james watson and it's always good to read other perspectives too but there's they're short books about this process and they're really interesting they're easy to read so i strongly encourage you to read that you could probably finish it in a day but anyway each strand of this double helix is made up of varying sequences of four molecular building blocks each of those building blocks contains a different base all forms of life use these same four building blocks which means they use the same genetic code to translate the information that's stored in the dna ultimately into proteins and proteins are the workhorse molecules of the cells genes are the recipe or instructions dna is the cookbook it's the recipe or instructions to make proteins that express your physical appearance and are responsible for carrying out metabolic processes and cell function if all organisms use these same building blocks and are responsible for self-function appearance physiology then what makes humans different from grapes because humans and grapes both have the same four bases or ingredients what makes a human different from a shark a grape or a pine tree pause the recording and write down in your notebook those questions what makes all of us different if we have only four ingredients among us and the ingredients are the same how is it that that we are so different why is a grape different than a pine tree so make a note in your notebook of that question all organisms use the same dna the same four bases that make up that dna so in turn our recipes our ingredients are the same so how do we account for the diversity of life think about that and see what you come up with the four different bases that are the building blocks for our dna are adenine thymine cytosine and guanine they're symbolized by the a t c and g a sequence of this letter code is like the sequence of letters in a word it has meaning dna carries or encodes the information required for an organism's growth and reproduction the two strands of the double helix are joined by interactions between bases the base pairing occurs only between a and t and c and g these base pairs kind of are arranged like the rungs on a ladder and then the backbone here of these strands kind of act as the sides of the ladder so this is two strands that are kind of twisted around each other to form this helix and we're going to talk about this in later chapters exactly what is this backbone made up of and how are these bonded together these are things to look forward to in your notebook please make sure that you write down the bases that pair together it's always the same in all organisms this this pairing is a key because it permits the dna to be copied and it pervert preserves the information encoded within the dna this is what is copied and this is just dna molecules are incredibly long and here we can see a depiction of the cell nucleus right here and this is where all of this dna is found it's always housed in eukaryotic cells in the nucleus the central dogma that i had you write earlier can be described as the flow of information of cells and the word dogma just simply means that it's expressing that this is a framework for understanding this flow so we have this central dogma of biology and it's a way that we understand how information is passed dna codes for rna and rna codes for proteins messenger rna specifically is the molecule that determines what molecular building blocks to use to make a protein and again we will go through that that's actually called translation and we'll be addressing that later in the semester proteins are important for most tasks in the cell proteins are form structural components of this cell and they promote chemical reactions in the cell so proteins are very very important what i want you to do now is try to summarize the relationship between dna genes proteins and the diversity of life that we see so pause the recording and in your notebook see what you come up with i want you to be critically thinking so here's an example of what i mean here's a a basic summary just so that you're getting the overall gist because you want to get the overall gist when you take your test you have to understand the overall gist of what we're discussing so that you can answer questions that are much more detailed so in summary we could say that the expression or appearance of an organism is a result of the proteins produced an example of differences in dna sequences can be seen in finch beak size and shape or it can be seen in the various lengths of a giraffe's neck changes in sequence lead to heritable variations that underlie the diversity of life and it's the different combinations of the four bases that results in the differences between species so that's an example of how you want to be thinking about these processes can you describe to grandma or your dog what you learned in your lecture now another point that's really important is try to read the chapter try to read the book pages that are listed in your lecture schedule prior to the recordings and reading it gives you a lot of information the lecture recording should help to answer some of the confusion from reading a textbook and then when we meet together you should be able to ask questions on things that you don't understand um and it's not that we're going to reteach an entire lecture during our meeting time so um just simply saying i didn't understand any of it isn't going to work you need to invest the time again look at that syllabus and see how much time you have to dedicate to this class so biology or science physics all these things uh really need a lot more time than an english class uh you can bang out a paper you know from you get home at 8 pm and by midnight you've submitted it so that's not going to be possible and achieve a decent grade in this class if that's how your if that's all the time that you have to permit to it all right so let's continue on again this is a just a little piece of dna to to blow up to show you um it's housed in the nucleus hopefully you all have that in your notes and you're getting this imprinted in your brain dna is found within the membrane bound nucleus of eukaryotic cells that c's and g's are paired together a's and t's are paired together the bases that are paired together make up the inner part here or the rungs of a ladder so to speak and the backbone makes up the outer sides of the ladder the entire library of genetic instructions that an organism inherits is called its genome the multinational human genome project required more than 15 years and about 3 billion dollars to assemble the first human genome sequence it was completed in 2001 and the president at the time was bill clinton and he stated that the human genome sequence was quote the most wondrous map ever produced by humankind end quote today sequencing of human genome is becoming a routine procedure and the cost is as low as a thousand dollars per genome it might be possible that someday we can each have our own genome sequence now that brings about a whole other topic and discussion on who would have access to your genome if you do have one but that is a good question and topic for another day so we will conclude our recording here