Bio Beyond: Genetic Replication Questions and Answers 100% Pass

Bio Beyond: Genetic Replication Questions and Answers 100% Pass Which bases pair in DNA? In the simulation below, build the strand that is complementary to the one shown. In this case, you are not replicating the strand but completing it. Thymine Adenine Guanine Cytosine Cytosine Thymine Thymine Adenine Guanine Thymine To continue, click on the image that you think best represents how DNA normally looks in the cell. First image Looking at the images, how many chromosomes are there in a typical human? 46 What do you notice about the chromosomes in both images? They come in pairs Why are chromosomes a poor way to think of how DNA is normally stored? DNA only looks like this during replication The top image, called a karyogram or karyotype, is from a human female, while the bottom one is from a human male. What major difference do you notice? The male has a set of mismatched chromosomes Thinking back to what you learned about genetics, what do the colored bands on the chromosome represent? Genes What do the images pointing to each colored band represent? Phenotypes From your exploration of DNA structure and biological macromolecules, what do you recall is the function of DNA in the cell? Information storage Which of the following characteristics are different between prokaryotic and eukaryotic chromosomes? Shape Where is the information stored in DNA? Base sequence Looking at the image to the right, what has to be done to chromatin before the information in it can be accessed? It has to be unwound to uncoiled DNA From chromatin, two major processes are needed to prepare for DNA replication. Watch the video at right - what processes are needed before new DNA can be made? DNA has to be uncoiled Bonds between bases have to be broken What type of bonds are broken when the strands are split apart? Hydrogen bonds It's important to know the base pairing rules for DNA before proceeding. Which of the following are valid pairings for DNA? Select all that apply A-T C-G One last question: How many bases do you think can be added to the new DNA strand each minute by the enzymes in your cells? 2 DNA Race C with G, G with C, T with A, A with T What is an isotope? An atom with a different number of neutrons than normal What does each model predict for the new DNA molecules? Connect each box on the left to one box on the right. No boxes are connected twice. Conservative model - One light and one heavy DNA Molecule -Two DNA molecules of different masses between light and heavy Semi-conservative model - Two DNA molecules halfway between light and heavy Dispersive Model - Two DNA molecules of different masses between light and heavy Is the DNA of the first generation grown in the presence of light nitrogen heavier or lighter than the original generation's DNA? Lighter What do the results Meselson and Stahl found for the first generation mean? All DNA used heavy and light nitrogen and has the same mass What do these results mean for the three proposed models? The semi-conservative model is supported Now that you've learned about how new and old DNA strands are matched during replication, you're ready to dive deeper into exactly how DNA replicates. After unwinding and breaking the bonds holding the two strands of DNA together, replication can begin. <--- Fork ---> However, DNA replication presented an interesting problem that wasn't solved until 1966: DNA is opened in one direction and DNA polymerases only work in one direction, but the two strands of DNA run in opposite directions (they are antiparallel). Why is this an issue? One DNA polymerase has to run away from the fork The strand where DNA polymerase moves away from the fork is called the lagging strand and is made in little pieces called Okazaki fragments, named after their discoverer, Reiji Okazaki. To continue, label the leading strand, lagging strand, and an Okazaki fragment in the image to the right. Leading strand on second box Okazaki fragment and lagging strand on last two boxes Why are Okazaki fragments made on the lagging strand? DNA polymerase has to copy away from the fork and jump back to copy more when the fork moves What has to happen to the Okazaki fragments after they are made? The fragments must be connected In the Replication Race, you learned that DNA Polymerase in humans copies about 33 bases per second. Assuming a total genome size of 3,000,000,000 bases, how many seconds are needed to copy the human genome once? How many minutes is that? .66667 Minutes How many hours is that? 25277.33 How many days is that? 1053.0553 How many years is that? 3 Data gathered on DNA replication in human cells indicate that the entire process takes just 8 hours - what is one way this could happen? There isn't just one polymerase copying the DNA How many polymerases must be used to reduce the time needed to copy DNA from about 25,000 hours to 8 hours? 3,125 In prokaryotes, there is typically only one origin of replication with two replication forks - areas where the DNA is opened up to be copied, like a bubble expanding. In eukaryotes, there can be many origins, each with two forks. Think back to what you learned about prokaryotes: why is it possible for prokaryotes to only have one origin? They usually have a smaller genome than eukaryotes Use your new knowledge and experience to put these stages of replication in order from first to last. One copy of genome exists DNA is uncoilded from its chormatin form the DNA double helix is straightened out to a ladder like state hydrogen bonds between bases are broken DNA polymerases make one continuous strand of new DNA and one fragmented strand of new DNA Okazaki fragments are connected two copies of the genome exist