Chapter 6 Cell Biology Comprehensive Review Exam Questions With 100% Verified Answers.

How does a DNA strand serve as a template for DNA replication? - correct answer 1) There is preferential binding between A-T and C-G to enable to act as a complementary strand. 2) Through this it can act as a template for its own replication. What does it mean that DNA replication is semi-conservative? - correct answer 1) Produces two complete double helices from the original DNA molecule 2) One strand is old while one is new which allows for old strands to remain intact for many generations. What is required for DNA synthesis to occur? - correct answer 1) DNA helix must be opened to expose unpaired bases (unwind) 2) Initiator proteins break hydrogen bonds separating a short length of DNA in replication origin areas. What is a replisome? - correct answer 1) Large protein complex/machine 2) Contains all the proteins need to copy the DNA 3) At replication forks, replication machine moves/walks along DNA to open DNa strands and replicate DNA 4) BIdirectional 5) 100 nucleotide pairs per seconds in human What is DNA helicase? - correct answer 1) Separates and open DNA strands so that proteins/enzymes have access to genetic materials 2) Utilizes ATP hydrolysis to pry apart the double helix What is DNA polymerase? - correct answer 1) Synthesizes new DNA using an old strand of DNA as a template 2) Only synthesizes in the 5' to 3' direction 3) Stays associated with DNA and moves along the template strand for many cycles of polymerization 4) At the replication fork, the two newly synthesized DNA strands are of opposite polarities. 5) Proofreading of this process occurs through the 3' strand which is why protein syntheiss occurs only in the 5' to 3' direction. What is the leading strand of DNA. - correct answer Made by continuous synthesis in the 5' to 3' direction What is the lagging strand of DNA? - correct answer Made by discontinuous lengths that are later joined covalently Since DNA polymerase works in the 5' to 3' direction there is always a leading and lagging strand. What are Okazaki fragments? - correct answer Small DNA pieces that are later joined together to form continuous strand What is primase? - correct answer An RNA polymerase that generates a short length of RNA about 10 nucleotides in length and provides base paired 3' end as starting point for DNA polymerase What is nuclease? - correct answer It breaks apart the RNA primer What is Repair polymerase? - correct answer Replaces RNA with DNA What is DNA ligase? - correct answer Joins 5' phosphate of new DNa to adjacent 3' hydroxyl end of the next. What are the steps involved in replication? - correct answer 1) A helicase binds to the ori sequence resulting in an open "bubble" DNA structure 2) Leading-strand primer synthesis starts 3) Leading-strand extension (elongation) 4) Further DNA unwinding 5) Further leading-strand extension 6) New lagging-strandp rimer synthesis 7) LAgging strand extension and ligation of "Okazaki" elements What is the Proliferating cell nuclear antigen (PCNA)? - correct answer "Donut" shaped molecule that enhances DNA synthesis elongation by associating with DNA polymerase? What is the Single-strand binding protein (SSB)? - correct answer It is known as RP-A (human) binds to single strand DNA in a cooperatie fashion and protects it from nucleases and straightens out any secondary structures. Preventing DNA from re-forming base pairs and keeping DNA elongated to serve as a template. What are the topoisomerases? - correct answer During DNA replication torsional tension is created ahead of the replication and if DNA becomes overwound it could stop replication so topoisomerase I and II resolves tension and tangled DNAs by making single or double stranded breaks in phosphate. DNA backbone is then resealed again. What is the difference between topoisomerase I and topoisomerase II? - correct answer Topoisomerase I makes a nick in one strand to relieve torsional stress while II makes a double DNA break and untangles DNA molecules. What does telomerase do? - correct answer It basically finishes the lagging strand when there is no more DNA to act as a template. What are mutations? - correct answer Permanent changes in the DNA that serve as an important role in evolution and gradual changes but if change occurs in important part DNA sequence it becomes problematic? What is sickle cell anemia? - correct answer Mutation causes fibrous precipitates and fewer red blood cells What are germ cell mutations? - correct answer It is passed to all cells.