36 terms. (A = adenine, etc). US HISTORY 2nd Semester Final Exam Study Guide PAR… 86 terms. Please refresh the page and try again. DNA: Definition, Structure & Discovery. One nucleotide of a DNA molecule consists of a phosphate group, a pentose (five-carbon) sugar called deoxyribose, and a nitrogenous base (adenine, thymine, guanine, cytosine). © These bases attach in place of the -OH group on the 1' carbon atom in the sugar ring. One of the nitrogenous bases in nucleic acids. Notice also that there are two different sizes of base. In other words, you are looking at the molecule from a bit above the plane of the ring. DNA is a double helix, while RNA is a single helix. Shares . The backbone of DNA is based on a repeated pattern of a sugar group and a phosphate group. Genetic test results can have implications for a person's health, and the tests are often provided along with genetic counseling to help individuals understand the results and consequences of the test. You will also notice that I have labelled the ends of these bits of chain with 3' and 5'. Whichever way you choose to draw this in 2-dimensions on paper, it still represents the same molecule in reality. . 44 terms. DNA helicase disrupts the hydrogen bonding between base pairs to separate the strands into a Y shape known as the replication fork. Biology DNA. The nucleotides are identical except for the base, which can be an adenine, thymine, guanine or cytosine. This material is aimed at 16 - 18 year old chemistry students. Both have sets of nucleotides that contain genetic information. These strong bonds form a sugar-phosphate backbone. One of the nitrogenous bases in nucleic acids. Thymine. Each chromosome contains a single DNA molecule. Our team of exam survivors will get you started and keep you going. On the outside of the double helix is the backbone which holds the DNA together. Notice that the individual bases have been identified by the first letters of the base names. sophianavarro21. Use the BACK button on your browser to return here later. For example, here is what the nucleotide containing cytosine would look like: Joining the nucleotides into a DNA strand. Both are right and, equally, both are misleading! Each of the four corners where there isn't an atom shown has a carbon atom. The diagram shows a tiny bit of a DNA double helix. Similarly, if the bottom of this segment of chain was the end, then the spare bond at the bottom would also be to an -OH group on the deoxyribose ring. Building a DNA chain concentrating on the essentials. Nucleotides are attached together to form two long strands that spiral to create a structure called a double helix. Live Science is part of Future US Inc, an international media group and leading digital publisher. DNA was first observed by a German biochemist named Frederich Miescher in 1869. I'm going to give you the structure of that first, because you will need it later anyway. "The point is not to store videos in bacteria," said study co-author Seth Shipman, a postdoctoral fellow at Harvard Medical School in Boston. Although DNA looks like very thin long strings under a microscope, it turns out that DNA has a specific shape. If you still aren't sure about this, look again at the page about drawing organic molecules. By convention, if you draw lines like this, there is a carbon atom where these two lines join. 08 December 2017. A quick look at the whole structure of DNA. I'm going to start with a diagram of the whole structure, and then take it apart to see how it all fits together. If the top of this segment was the end of the chain, then the phosphate group would have an -OH group attached to the spare bond rather than another sugar ring.