In eukaryotes, DNA replication: A) starts from multiple origins on each chromoso
ID: 84966 • Letter: I
Question
In eukaryotes, DNA replication: A) starts from multiple origins on each chromosome B) is catalyzed entirely by DNA polymerase III C) does NOT require primer, only telomerase D) does NOT require any remodelling of chromatin When a 18 kb fragment of DNA is cleaved with HindIII the fragments formed are 10 and 8 kb. AluI cleavage produces fragments of 15 and 3 kb. A double digest with Hindlll and AluI produces fragments of 8, 7 and 3 kb. Which of the following is true? A) The AluIl site is in the 10 kb Hindlll fragment. B) The AluI site is in the 8 kb Hindlll fragment. C) The Hindlll site is in the 3 kb AluI fragment. D) AluI cleaves at 2 sites within the 18 kb fragment PCR uses: a) E. coli DNA polymerase b) S1 nuclease c) one incubation temperature over 90 C d)electrophoresis E) all of the above In E. coli, DNA replication is: a) conservative b) unidirectional C) accomplished by synthesis in the 5' to 3' direction D) started from several origins E) all the above are true Telomerase: A) can be active in immortal cells B) contains RNA C) adds bases to the ends of chromosomes D) all of the above A Southern blot transfers ________ to a nitrocellulose membrane. a) protein b) DNA c) RNA In vertebrate genes, dispersed promoters: A) start transcription at one specific base pair B) are associated with genes that are transcribed constitutively C) are rare or absent D) all the above Which of the following is FALSE?Explanation / Answer
33. Ans-a
a) Generally DNA replication in eukaryotes is initiated from specific origin called origins of replication . In prokaryotic cells, there is only one point of origin, replication occurs in two opposing directions at the same time, and takes place in the cell cytoplasm. Eukaryotic cells on the other hand, have multiple points of origin, and use unidirectional replication within the nucleus of the cell.
b) In eukaryotes, initiation is the first stage of DNA. There are several types of DNA polymerase that play a role in DNA replication and synthesizes to identical DNA strand from single stranded DNA
c) A primer is a short stranded RNA or DNA. It serves as a starting point for DNA synthesis. The synthesis of a primer is required because the enzymes that synthesize DNA called DNA polymerases can attach new DNA nucleotides only in existing strand of nucleotides. Therefore, RNA primer helps to prime and leave a foundation for DNA synthesis.
d) In eukaryotic DNA is wound into a complex called chromatin and this complex can be "opened” at the time of specific genes expression. This ‘’opening ‘’ process is called chromatin remodeling, and it is play an importance role for the proper functioning of all eukaryotic cells.
35. Ans- d
a) In PCR reaction, DNA polymerase enzyme is required to make new strands of DNA from using template strand. The DNA polymerase used in PCR is called Taq polymerase, which is isolated from Thermus aquaticus. T. aquaticus is a bacterium that lives in hot springs and thermo stable and able to withstand the protein-denaturing conditions at high temperature during PCR. Thus,it replaced the DNA polymerase from E. coli which is originally used in PCR.
b) S1 Nuclease is an endonuclease that degrades single-stranded nucleic acids including DNA, RNA or DNA/RNA and also introduce single-stranded nicks and breaks in duplex DNA, RNA and DNA/RNA. S1 Nuclease specially targets DNA over RNA. This endonuclease is used in gel electrophoresis for removal of single-stranded regions from double-stranded DNA .
c) The steps of PCR include:
Denaturation (96°C) that separate, or denature, the DNA strands
Annealing (55 - 65°C) that cool the reaction so that primers can bind to their complementary sequences on the single-stranded template DNA.
Extension (72°C) that raise the reaction temperatures so that Taq polymerase extends the primers, synthesizing new strands of DNA.
d) After PCR, the results of a PCR reaction are visualized in gel electrophoresis in which fragments of DNA are pulled through a gel matrix by an electric current and separates DNA fragments according to size.
36.ans- c
a) Prokaryotic DNA is circular and and semiconservative in nature.
b) it is bidirectional
c)The template DNA is unwound by DNA helicase and synthesized in 5’-3’ direction
d) replication starts from a single point of origin
37.Ans- d
a)...Telomerase is also called terminal transferase and active in normal stem cells and most cancer cells and normally absent in very low levels somatic cells.
b) Telomerase is a ribonucleoprotein
c) Telomerase adds a species-dependent telomere repeat sequence to the 3' end of telomeres.
38. Ans-b
A Southern blot is a method used in molecular biology which is used for detection of a specific DNA sequence in DNA samples.
39.Ans- b
a) Dispersed transcription have multiple weak start sites over a broad region of about 50 to 100 nucleotides.
b) Dispersed transcription is observed in constitutive promoters in CpG islands
c) Dispersed transcription is the most common type of transcription in vertebrates.