Define/Explain the following:
$1.$ Nucleotide
$2.$ Central Dogma

Select the correct statement from the following.

In Lederberg's replica plating experiment,what should be used to obtain streptomycin-resistant strains?

Consider the following four statements $(a-d)$ and select the option which includes all the correct ones only $:-$
$(a)$ Transcription and translation can be coupled in bacteria.
$(b)$ The split gene arrangements represent the advanced feature of the genome.
$(c)$ The process of splicing represents the dominance of $\text{RNA-}$world.
$(d)$ The presence of introns in split gene is reminiscent of antiquity.

Given below are two statements:
Statement $I$: Transfer $\text{RNAs}$ and ribosomal $\text{RNA}$ do not interact with $\text{mRNA}$.
Statement $II$: $\text{RNA}$ interference $\text{(RNAi)}$ takes place in all eukaryotic organisms as a method of cellular defence.
In the light of the above statements,choose the most appropriate answer from the options given below.

Read the following statements carefully and choose the correct statements.
$(A)$ In a transcription unit,the promoter is located at the $5'$ end of the coding strand.
$(B)$ The single strand $DNA$ having the polarity $5' \rightarrow 3'$ is the template strand.
$(C)$ $RNA$ polymerase binds to the operator during transcription.
$(D)$ Single base $DNA$ differences occurring in humans are called Single Nucleotide Polymorphisms $(SNPs)$.