Bio Beyond: Genetic Replication Questions With Complete Solutions

Bio Beyond: Genetic Replication Questions With Complete Solutions - ANSWER - Where is the information stored in DNA? - ANSWER -Base sequence Looking at the image to the right, what has to be done to chromatin before the information in it can be accessed? - ANSWER -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? - ANSWER -DNA has to be uncoiled Bonds between bases have to be broken What type of bonds are broken when the strands are split apart? - ANSWER -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 - ANSWER -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? - ANSWER -2 DNA Race - ANSWER -C with G, G with C, T with A, A with T What is an isotope? - ANSWER -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. - ANSWER -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? - ANSWER -Lighter What do the results Meselson and Stahl found for the first generation mean? - ANSWER -All DNA used heavy and light nitrogen and has the same mass What do these results mean for the three proposed models? - ANSWER -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. - ANSWER ---- 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? - ANSWER -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. - ANSWER -Leading strand on second box Okazaki fragment and lagging strand on last two boxes Why are Okazaki fragments made on the lagging strand? - ANSWER 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? - ANSWER -The fragments must be connected