Question

In: Biology

2.a) RNA polymerase adds RNA monomers to where? Select one: a. 3' end of the growing...

2.a) RNA polymerase adds RNA monomers to where?

Select one:

a. 3' end of the growing RNA transcript

b. 5' end of the growing RNA transcript

c. 5' end of the DNA template

d. 3' end of the DNA template

b) The "charging" of tRNA requires which of the following? Select all that apply.

Select one or more:

a. ATP

b. Aminoacyl tRNA synthetase

c. tRNA lacking an amino acid

d. aminoacyl tRNA

c) Which of the following is/are methods of chromatin remodelling? Select all the apply.

Select one or more:

a. DNA methylation

b. Histone modification

c. tRNA alteration

d. Nucelosome formation

Expert Solution

1) The correct option is (a) 3' end of the growing RNA transcript.

Transcription is a process in which the information in a DNA strand is copied into a new strand of RNA (mRNA). It is facilitated by an enzyme called RNA polymerase which acts only in 5' to 3' direction. Therefore, 3' to 5' directionally strand will act as a template strand. Hence, the new RNA monomers are added to the 3' hydroxyl end of the growing strand by RNA polymerase.

Option (b) is incorrect because RNA polymerase acts in a 5' to 3' direction and therefore a new monomer will be added to the 3' end and not to the 5' end.

Option (c) and (d) are incorrect because in transcription, synthesis of RNA from DNA takes place and hence new monomer cannot be added to a DNA template strand.

2) The correct options are (a),(b) and (c).

The "charging" of tRNA is also know as activation of amino acid or aminoacylation. In this process attachment of an amino acid to its tRNA takes place. There are two enzymes that facilitate this process and they are Aminoacyl transferase and Aminoacyl t-RNA synthetase. Aminoacyl transferase facilitates the binding of amino acid to ATP to form AMP-amino acid and then Aminoacyl tRNA synthetase facilitates binding of this AMP-aminoacid to tRNA to form an aminoacyl tRNA or a charged tRNA.

Option-d is incorrect because Aminoacyl tRNA is already charged and thus does not need charging.

3) The correct options are (a), (b) and (d).

Chromatin remodeling is the modification or the rearrangement of chromatin from a condensed state to a transcriptionally accessible state. There are various methods of chromatin remodeling and they are:-

i) Histone modification - It is done by specific genes like histone acetyl transferases, deacetylases, etc. These modifications affect the binding of histone and DNA and thus facilitate loosening or tightening of the remodeled DNA.

ii) DNA methylation is an epigenetic process and it regulates gene expression. Methylation of cytosine residues by methyltransferase represses transcription and thus inhibit the gene expression.

iii) ATP dependent chromatin remodeling is done by either moving, ejecting or restructuring or reforming of nucleosome in order to regulate expression.

Option-(c) is incorrect because tRNA alteration has no role in chromatin remodeling as tRNA itself formed after transcription that takes place after chromatin remodeling. It helps mainly in the transcription process and not before it.

gladiator answered 1 year ago

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