Question

Under physiological conditions, most DNA exist in which form? a. DNA A b. b. DNA B c. c. DNA C d. d. DNA Y e. DNA Z

What type of RNAs directs the methylation of eukaryotic rRNA? a. Small nucleolar b. small nuclear c. ribozyme d. pre mRNA e. miRNA

Ultra violet light causes formation of (a) thymidine dimers (b) 6’-4’ photoproduct (c) cyclobutane ring (d) all of the above (e) both ‘a’ and ‘b

Which of the following enzymes is/are involved in the removal of RNA primers of Okazaki fragments? (a) RNase H1 (b) replication protein A (c) flap endonuclease 1 (d) both a and b (e) both a and c

Answer 1

1)B DNA B

generally three forms are mainly present that is A form B form and Z form

but the most common form present in DNA at neutral pH and physiological salt conditions is B form

2)A SMALL NECLEOLAR

small nucleolar RNAs(snoRNAs) are aclass of small RNA molecules that primarily guide two different type of rRNA modifications(METHYLATION and pseudouridylation)

3)ALL THE ABOVE

two main products of UV light are cyclobutane pyrimidine dimers (CPDs including thymine dimers) and 6-4 photo products

thymidine is nothing but pyrimidine deoxynecleoside

so cyclobutane ring ,thymidine dimers and 6-4 photoproducts are formed

4) C FLAP ENDONUCLEASE 1

flap endonuclease 1 (FEN1) is responsible for processing okazaki fagments.

it works with DNA polymerase to remove the RNA primer of okazaki fragments

thus FEN1 function is neccessary for okazaki fragment maturation in forming a long continous DNA strand.