1: B,C, E and F are wrong 2: B,C,D are wrong 4: B is wrong 7: B,D and E are wron

Question

1: B,C, E and F are wrong 2: B,C,D are wrong 4: B is wrong 7: B,D and E are wrong Please help me all quétions and explain. Thank you : 1. Researchers noted that about half of all species of bacteria contain small segments of DNA of about 20-50 base pairs derlved from plasmids or viruses. The phrase clustered regular interspaced short palindromic repeats (CRISPR) describes the organization of these viral DNA segments in the bacterial genome. Bacteria use cRispR to: (sevect an that apply O transcribe RNA that combines with a protein that has a RNA-cleaving fu "remember" the first time it was infected with a virus. transcribe RNA that combines with a protein that has a DNA-cleaving function identify viral DNA by complementary base pairing with RNA. copy part of the bacteria genome and incorporate it into a viral genome. identify viral DNA by complementary base pairing with template DNA. 3 2. Cas9 cleaves both strands of the target DNA. Which of the following could occur when cells will try to repair the damage after cleavage by Cas9? (Select all that a no change in the targeted gene deletions of the targeted gene the insertion of a DNA sequence into the targeted gene mutations that result in changes to the open reading frame (ORF) of the targeted gene loss-of-function mutations within the targeted gene

Explanation / Answer

1.

"remember" the first time it was infected with a virus. Bacteria develop memory to distinguish different viruses which have infected them earlier. It like memory immune response.

transcribe RNA that combines with a protein that has a DNA-cleaving function. Transcribed RNA combines with CRISPR-associated protein 9 (Cas9) which can cleave DNA.

identify viral DNA by complementary base pairing with RNA. Transcribed RNA combines with Cas9, and guides it to take at target DNA site and hybridize using complementary base pairing.

2.

All the options are correct except

"deletions of the target gene." The repair process may result in mutations but not the complete deletion of target gene.

There are two types of repair mechanisms: non-homologous end joining, NHEJ (error-prone) and homology-directed (error free). NHEJ may result in loss of free bases from cleavage site, mutations resulting in change in ORF, or loss of function mutation.

4.

4, 3, 5, 1, 2.

sgRNA combined with Cas9 to form the complex. The complex then scans for PAM sites in the target sequence and binds when site is found. Cas9 unzips the DNA allowing sgRNA to form complementary base pairing with target DNA. Once it is bind perfectly, Cas9 makes double stranded breaks in DNA.

7.

Bind target DNA by interacting with PAM site through arginine residue of Cas9.

Bind sgRNA to form sgRNA-Cas9 complex.

Cleave target DNA as Cas9 is DNA endonuclease.

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