Question

Fill in the blank:

1. During chromosome replication, the _________ enzyme synthesizes short RNA primers that get extended to form the ___________ fragments. This process uses the __________ strand as the template.
2. Type II topoisomerases such as DNA gyrase change the LINKING number of DNA in increments of ____. They use a _________ amino-acid side chain at the active site to form a ___________ linkage to the broken DNA strands.
3. The protein core of a nucleosome consists of ___ copies each of __________ proteins ____, _____, _____, and ______. The ______________ protein binds DNA where it enters and exits the nucleosome and promotes DNA compaction.

Multiple choice or true/false- circle the correct choice, presented in parentheses,

1. DNA wrapped around a histone core particle forms a (plectonemic) (solenoidal) supercoiled structure.
2. Most DNA in cells is (underwound) (overwound) relative to it’s relaxed state.
3. Type I topoisomerases can concatenate or link together two circular DNA molecules. (true) (false)
4. Acetylation of histone tails usually occurs on (lysine) (arginine) (serine) (cysteine) residues.
5. The “histone fold” consists entirely of (alpha helices) (beta sheets) (unstructured random coil).
6. There are typically (1) (2) (3) copies of the replicative polymerase, Pol III, at the E. coli replication fork.
7. The most abundant DNA polymerase in the E. coli cell is Pol I, accounting for ~99% of total measurable polymerase activity [that part is true]. Mutant E. coli cells that lack this enzyme are not viable. (true) (false)
8. Presence of the beta-sliding clamp enhances the (processivity) (dNTP recognition) (5’->3’ exonuclease activity) (proofreading ability) of DNA Pol III.
9. “Firing” the origin involves the regulated oligomerization of (DnaA) (SeqA) (OriC) (Dam methylase) on DNA at the origin of replication.
10. A protein that binds newly replicated origins of replication in E. coli and prevents re-initiation of DNA synthesis is (DnaA) (SeqA) (OriC) (Dam methylase)

Answer 1

DNA Pol

Okazaki fragments

5'-3' strand

Twist number (T_{​​​​​​w}) i.e the total number if helical turns in the DNA .

Tyrosine

Transient phosphotyrosine

2 copies

Histone proteins

H2A ,H2B , H3 and H4

Linker histone protein H1

MCQ's / True - false

* Solenoidal form because in super coiled form DNA exist in two confirmations either zig-zag or solenoidal form .

* Underwound .

* False beacuse type1 topiisomerase can separate two lonked circular DNA molecules .

* Lysine

* The histone fold consist entirely of unstructured random coils .

*Only (1) single copy of pol lll .

* Processivity

* DnaA

* Seq A negatively regulates the DNA proliferation .

( For all above answers no explanation is needed beacuse all are facts based on literature ) .