Which bond connects the phosphate group to the sugar in a nucleotide?
A phosphoester bond connects the phosphate group to the 5-prime carbon of the pentose sugar. In a DNA strand, the linkage between two nucleotides involves two such bonds, forming a phosphodiester linkage.
Question 42 of 668
📘 CLASS XII
Uracil is present in RNA instead of which base found in DNA?
In RNA, Uracil replaces Thymine. Both Uracil and Thymine are pyrimidines that pair with Adenine. Thymine is essentially 5-methyl uracil, making it chemically more stable for DNA storage.
Question 43 of 668
📘 CLASS XII
According to Chargaff’s rule, in a double-stranded DNA?
Chargaff’s rule states that in double-stranded DNA, the ratio of purines to pyrimidines is 1:1. This means the amount of Adenine plus Guanine (Purines) equals the amount of Cytosine plus Thymine (Pyrimidines). Also, A=T and G=C.
Question 44 of 668
📘 CLASS XII
The negatively charged DNA is wrapped around a positively charged histone octamer to form a?
The fundamental unit of chromatin packaging is the nucleosome. It consists of negatively charged DNA wrapped approximately 1.75 times around a positively charged histone octamer core, resembling "beads on a string".
Question 45 of 668
📘 CLASS XII
A typical nucleosome contains how many base pairs of DNA helix?
A typical nucleosome contains approximately 200 base pairs of DNA helix wrapped around the histone octamer. This packaging compacts the DNA significantly.
Question 46 of 668
📘 CLASS XII
Which organism has approximately 4.6 x 10^6 base pairs?
Escherichia coli (E. coli) has a genome size of approximately 4.6 million base pairs (4.6 x 10^6 bp). In comparison, the human haploid genome is much larger at 3.3 x 10^9 bp.
Question 47 of 668
📘 CLASS XII
In the Griffith experiment, which strain of Streptococcus pneumoniae was virulent?
The S-strain (Smooth) was virulent because it possessed a polysaccharide mucous coat that protected it from the host immune system, causing pneumonia. The R-strain (Rough) lacked this coat and was non-virulent.
Question 48 of 668
📘 CLASS XII
Biochemical characterization of the transforming principle showed that transformation was inhibited by?
Avery, MacLeod, and McCarty showed that adding DNase (an enzyme that degrades DNA) to the heat-killed S-strain extract stopped the transformation of R-strain bacteria. This proved that DNA was the substance causing transformation.
Question 49 of 668
📘 CLASS XII
RNA is considered the first genetic material because?
The "RNA World" hypothesis suggests RNA was the first genetic material because it can store genetic information (like DNA) and catalyze chemical reactions (like proteins/enzymes, e.g., Ribozymes). DNA evolved later as a more stable storage molecule.
Question 50 of 668
📘 CLASS XII
The discontinuously synthesized fragments on the lagging strand are called?
Because DNA polymerase can only synthesize in the 5-to-3 direction and the two DNA strands are antiparallel, one strand (lagging strand) must be synthesized in short, backward bursts. These short segments are called Okazaki fragments.
