18. DNA is composed of ... a) pyrimidines, purines, phosphate groups and deoxyribose sugar. b) pyrimidines, purines, phosphate groups and ribose sugar. c) ribosomes, tRNA, mRNA. d) proteins only. e) amino acids only. 19. Which of the following mutations would be expected to have the most harmful effect on the resulting protein? a) a base deletion near the start codon. b) a base deletion near the stop codon. c) a three-base addition near the stop codon. d) a base substitution. 20. DNA ligase joins ________________________ by creating ________________________ bonds a) Okazaki fragments ; peptide b) Okazaki fragments ; polypeptide c) Okazaki fragments ; phosphodiester d) DNA pieces; phosphodiester e) RNA fragments; phosphodiester 21. Recombinant DNA is best described as a fragment of DNA a) a fragment of DNA composed of sequences originating from at least two different sources b) a palindromic sequence of DNA c) useful in Biotechnology d) all of the above choices 22. The function of the kidney is... a) to filter nutrients from the food we eat b) to filter wastes from blood c) to assist with muscle contractions d) to control enzyme activity e) to produce hormones for digestion 23. Which of the following is not a structure of a nephron? a) the Loop of Henle b) the proximal convoluted tubule c) the urinary bladder d) Bowman's capsule e) all are structures of the nephron 24. The part of the eye that supplies the cornea with nutrients is called the a) the fovea centralis b) aqueous humour c) sclera d) vitreous humour 25. While the body is moving, balance is maintained by the fluid-filled ossicles A) the three fluid-filled semicircular canals B) the basilar membrane C) the organ of Corti D) the cochlea 26. The hormone aldosterone: a) causes the kidneys to increase water reabsorption b) causes an increase in Na+ reabsorption from the distal tubule and collecting duct c) is produced in the medulla of the adrenal glands d) is responsible for maintaining the pH of blood e) Is responsible for causing the release of angiotensin
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Step 1:** Identify the components of DNA mentioned in the explanation: - Purines - Pyrimidines - Phosphate group - Deoxyribose sugar ** Show more…
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29. The top diagram is of a transcription. Select DNA template used in transcription of mRNA. a) strand A c) both A and B are templates b) strand B d) neither A nor B 30. DNA polymerase unlike RNA polymerase a) catalyzes formation of phosphodiester bonds b) uses deoxyribonucleotides c) catalyzes synthesis of a new DNA strand in 5' - 3' direction d) B and C e) A, B and C 31. The strain of E. coli is resistant to antibiotic tetracycline. The resistance gene is on E. coli's plasmid. Assume that tetracycline resistant E. coli was mixed with Staphylococcus aureus. The mixed population continues growing and reaches stationary phase. Is it possible that S. aureus develops resistance to tetracycline? a) Yes, but only if mutation occurs in S. aureus transport mechanism gene. b) Yes. S. aureus cells could become transformed with E. coli plasmids. c) Yes. S. aureus cells could obtain E. coli plasmid through conjugation. d) No, because they are different bacterial species. 32. Transcription is the process that in bacterial cells creates a) RNA molecules b) proteins c) enzymes d) B and C 33. During DNA replication single nucleotide got deleted. The nucleotide was within the second codon of a gene that encodes an enzyme. What will the consequence of the deletion of a single nucleotide on gene expression be? a) Encoded enzyme will have one less amino acid b) Encoded enzyme will have amino acid sequence that differs from the un-mutated, but will maintain the properties of an enzyme. c) The protein product will have different amino acid sequence and will not act as an enzyme d) Encoded enzyme will differ from un-mutated version in one amino acid only 34. Bacterial virus, bacteriophage, is essential for a) bacterial transformation process c) bacterial transduction b) bacterial conjugation d) bacterial replication 35. Streptococcus pyogenes is β hemolytic microorganism. When grown on sheep blood agar plate the colonies of this microorganism a) form cloudy, olive green zone around each colony b) excrete hemolysins c) do not create distinct zone around colony d) A and B e) B and C
Sri K.
30) According to the complementary base pairing all the following pairs are possible except: a) G≡C b) A=U c) A=T d) G≡A 31) The enzyme that binds to DNA during replication is: a) RNA polymerase b) ATPase c) DNA polymerase d) DNA replicase 32) The enzyme that binds to DNA during transcription is: a) RNA polymerase b) ATPase c) DNA polymerase d) DNA replicase 33) A sequence of 3 nucleotides on mRNA that directs the placement of AA in protein synthesis is called: a) codon b) anticodon c) Intron d) Exon 34) A sequence of 3 nucleotides on tRNA that directs the placement of AA in protein synthesis is called: a) codon b) anticodon c) Intron d) Exon 35) A change in DNA sequence is called: a) chromosomal aberration b) mutation c) trisomy d) alteration 36) The RNA that forms the Ribosome is: a) mRNA b) tRNA c) rRNA d) nRNA 37) The product of transcription is: a) RNA b) DNA c) mRNA d) protein 38) The product of replication is: a) RNA b) DNA c) mRNA d) protein 39) The first step in translation is: a) tRNA binding to mRNA b) mRNA binding to tRNA c) mRNA binding to ribosomal unit d) tRNA binding to ribosomal unit 40) Amino Acids that are to be used in synthesizing a protein are carried by: a) mRNA b) rRNA c) tRNA d) DNA 41) Translation ends when the __________ reach to a stop codon: a) RNA polymerase b) DNA polymerase c) mRNA d) Ribosome 42) The sections of the RNA that must be removed before the molecule leaves the nucleus are called: a) codons b) anticodons c) exons d) introns 43) The protein coding region present on a gene is located after the: a) promoter region b) termination region c) regulatory region d) codons 44) When enzymes cut DNA molecules without producing open staggering ends then this type of enzyme cutting produces: a) Sticky ends b) Blunt sections c) 5' Overhang d) 3' Overhang 45) The product of translation is: a) RNA b) DNA c) mRNA d) protein
Adi S.
In Glenn Croston and his colleagues studied the relation between chromatin structure and transcription activity. In one set of experiments, they measured the level of in vitro transcription of a Drosophila gene by RNA polymerase II in the presence of DNA and various combinations of histone proteins (G. E. Croston et al. 1991. Science 251:643-649). First, they measured the level of transcription of naked DNA, with no associated histone proteins. Then they measured the level of transcription after nucleosome octamers (without H1) were added to the DNA. The addition of the octamers caused the level of transcription to drop by $50 \% .$ When both nucleosome octamers and H1 proteins were added to the DNA, transcription was greatly repressed, dropping to less than $1 \%$ of that obtained with naked DNA, as shown in the table below. GAL4-VP16 is a protein that binds to the DNA of certain eukaryotic genes. When GAL4-VP16 is added to DNA, the level of transcription by RNA polymerase II is greatly elevated. $$\begin{array}{cc} \text { Treatment } & \text { Relative amount of } \\ \text {} & \text { transcription }\\ \text { Naked DNA } & 100 \\ \text { DNA + octamers } & 50 \\ \text { DNA + octamers $+\mathrm{H}_{1}$ } & <1 \\ \text { DNA + GAL4-VP16 } & 1000 \\ \text { DNA + octamers + GAL4-VP16 } & 1000 \\ \text { DNA + octamers $+\mathrm{H} 1+$ GAL4-VP16 } & 1000\\ \end{array}$$ Even in the presence of the H1 protein, GAL4-VP16 stimulates high levels of transcription. Propose a mechanism by which the H1 protein represses transcription and by which GAL4-VP16 overcomes this repression. Explain how your proposed mechanism would produce the results obtained in these experiments.
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