BIOMG 3350 Final Exam Questions With Correct Answers

BIOMG 3350 Final Exam Questions With Correct Answers Describe the structure of a nucleotide. What is the difference in the structure between RNA and DNA? How are nucleotides connected in DNA? - answerpentose sugar phosphate group connected at the fifth carbon nitrogenous base connected at the first carbon OH at carbon 3 DNA has H at carbon 2 RNA has OH at carbon 2 Nucleotides are connected by a 3',5' phosphodiester linkage. This means that the 3 carbon of one nucleotide is connected to the phosphate on the 5 carbon of another nucleotide. What is the usual key feature of the origin of DNA replication for bacteria? - answerAT-rich segments because these bonds are easier for helicase to separate. AT has only two hydrogen bonds, while CG has three hydrogen bonds. Describe the steps of DNA replication. Be sure to discuss leading and lagging strands. - answer1. Helicase separates DNA strands (breaks the H-bonds holding bases together) - helicase movement causes a replication fork 2. Topoisomerases (DNA gyrase) reduces strain and supercoils, allowing helicase to continue separating 3. Single Strand Binding proteins (SSBs) stabilize/protect the isolated strands 4. RNA primer (needed to start DNA replication) is added by primase 5. DNA polymerase III adds nucleotides in the 5' to 3' direction - the leading strand has 5' to 3' synthesis in the same direction as the replication fork movement. continuous - the lagging strand has 5' to 3' synthesis in the opposite direction as the replication fork movement. Because of this the lagging strand needs multiple RNA primers to form Okasaki fragments. discontinuous EXAM STUDY MATERIALS July 30, 2024 11:26 AM 6. DNA polymerase I removes the RNA primer and replaces it with DNA 7. DNA ligase seals the nicks after the RNA primer is replaced with DNA What are the purines and pyrimidines? What's the difference? - answerpyrimidines - thymine, cytosine, uracil purines - adenine, guanine pyrimidines are 1 six carbon ring structures. purines are 2 ring structures (1 six carbon, 1 five carbon) DNA can be highly distorted during replication/transcription, but is resolved by this enzyme - answertopoisomerase What are important structural components of chromosomes? - answercentromere = a DNA sequence that functions during cell division as an attachment point for proteins that link the chromosome to the mitotic spindle telomeres = sequences at the ends of eukaryotic chromosomes that help stabilize the chromosome (highly repetitive sequences associated with these) gene = a segment of a DNA molecule that containsthe information required for the synthesis of afunctional biological product, whether protein orRNA Why don't bacterial cells have telomeres? - answerBacterial cells are circular, while eukaryotic cells have exposed ends (and thus need to be protected by these sequences). introns and exons - answerIn most eukaryotic genes, coding regions (exons) are interrupted by noncoding regions (introns). During transcription, the entire gene is copied into a pre-mRNA, which includes exons and introns. During the process of RNA splicing, introns are removed and exons joined to form a contiguous coding sequence. ~99% of human genome does not code for genes what are the functions of the four classes of RNA? - answerseveral classes of RNA: - ribosomal RNAs (rRNAs) = components of ribosomes - messenger RNAs (mRNAs) = intermediates in protein synthesis - transfer RNAs (tRNAs) = adapter molecules that translate the information in mRNA into a specific amino acid sequence - noncoding RNAs (ncRNAs) = wide variety of functions EXAM STUDY MATERIALS July 30, 2024 11:26 AM Why is RNA less stable than DNA? - answerIt has an extra Hydroxyl Group (OH) on the 2' carbon making it more likely to participate in chemical reactions The proximity of the OH group to the phosphodiester bond means that the H may react with the phosphate group, causing the bond between two nucleotides to break How in DNA denatured? Can this be fixed? - answerdenaturation, or melting, of the double helix:- due to pH extremes or high temperatures (useful in experiments) - disrupts hydrogen bonds and base-stacking interactions Yes, can be fixed. anneal = process by which two strands spontaneously rewind when temperature or pH is returned to its normal range- two-step process What are the adenine nucleotides? - answerNucleotides Carry Chemical Energy in Cells hydrolysis of nucleoside triphosphates provides chemical energy- ATP is the most widely used. ADP also cAMP are is another nucleotide that is a secondary messenger Describe the structure of the strand (macro-level structure) of DNA and RNA - answerDNA is primarily a right-handed two-stranded helix (secondary structure),whereas RNA has lots of secondary and tertiary structure (interactionsbeyond just a helix) but is a single strand. Describe DNA repair (proofreading, mismatch, and damage) - answerDNA is degraded by nucleases. exonuclease = enzyme that can remove nucleotides from the strand starting from one end of the strand. endonuclease = enzyme that can remove nucleotides from the middle of the strand Proofread: During DNA synthesis, most DNA polymerases "check their work," fixing the majority of mispaired bases in a process called proofreading. DNA pol I and DNA pol III have 3' to 5' exonuclease capabilities. This allows them to proofread and remove incorrectly matching nucleotides and replace them right away. Mismatch repair: Immediately after DNA synthesis, any remaining mispaired bases can be detected and replaced in a process called mismatch repair. First, a protein complex (group of proteins) recognizes and binds to the mispaired base. A second complex cuts the DNA near the