🧬 Biochemistry Solved MCQs with Answers

Practice 1490 approved 🧬 Biochemistry questions with verified answers from the 🧬 Medical Science subject for Pakistan exams.

1490 solved MCQs

Nucleosome isAnswer: An octamer of four histones without H1 protein The DNA polymerase in bacteria, responsible for DNA synthesis isAnswer: Polymerase III In a typical electrophoresis experiment, larger fragments of DNA move moreAnswer: Slowly, so they appear nearer the top of a gel photograph 30 nm wide helix with five or six nucleosomes per helix is known asAnswer: Solenoid Which of the following is used to determine the appropriate stringency (Wallace rule)?Answer: Tm = 4 x (No.of G:C base pair) + 2 x (No.of A:T base pair) One hypothesis of DNA replication suggested that the parental DNA molecules are broken into fragments. Both strands of DNA in each of the daughter molecules are made up of an assortment of parental and new DNA. This statement refers to which hypothesis?Answer: Dispersive theory DNA polymerases I also hasAnswer: 3'-5'exonuclease activity Without telomerase, what would happen to the ends of chromosomes after each round of replication?Answer: Chromosomes would become progressively shorter The melting of 40-45 bp at the oriC site of E. coli requiresAnswer: DNA + ATP + HU Overwinding or overtightening of DNA during replication is caused and removed byAnswer: DNAb, gyrase How does ethidium bromide interact with DNA?Answer: It intercalates between bases Number of times the two DNA strands are interwined in circular DNA and is known asAnswer: Linking number The enzyme responsible for breaking the hydrogen bonds, and thus separating the DNA strands during DNA synthesis isAnswer: Helicase Which of the following species lack a 'classical' histone H1?Answer: Saccharomyces cerevisiae Which of the following is correct?Answer: All of these The size of a linear DNA fragment in a gel can be estimated byAnswer: Comparison with a molecular weight standard such as Hind III digested phage lambda Which of the following are short nucleotides strands made by DNA polymerase working in the opposite direction of the replication fork?Answer: Okazaki fragments Which of these drugs bind to DNA and cuts it, producing hydroxyl radicals?Answer: Bleomycin Replication in E. coli is initiated by the generation of short RNA primers usingAnswer: Both (a) and (b) DNA replication results inAnswer: Two DNA molecules such that each one contains a strand of the original Which enzyme catalyzes the elongation of DNA molecules?Answer: DNA polymerase What is the IUPAC code for an A, C, T ambiguity in a nucleic acid sequence?Answer: H There is a single origin for DNA replication in bacteria. How many origins of replication are found in the much larger genomes of eukaryotes such as mammals?Answer: Thousands and tens of thousands Automated DNA sequencing uses the chain termination methodAnswer: But with an oligonucleotide primer labeled with a fluorescent dye Okazaki fragments occur on the __________ and are bonded together by __________Answer: Lagging strand, ligase The RNA primers used to initiate replication in E. coliAnswer: Are removed by Pol I An enzyme that recognizes foreign DNA, and results in a cut in that DNA is calledAnswer: Reverse transcriptase Which of the following is an active site on its single polypeptide chain for DNA Polymerase I?Answer: 5' → 3' polymerase Which of the following is not a structural motif in DNA binding proteins?Answer: TFIID DNA with a G-C content of 50% will melt at approximatelyAnswer: 90 °C