Question

I need the explanation for why is this the answer ! please. And answer the other ones if you can.

3) If a species contains 23% A in its DNA, what is the percentage of guanine it would contain? A)23% B)46% C)25% D)44% E)27% 4) A nucleotide contains ADNA and RNA. Ba sugar and a phosphate. C)complementary purines and pyrimidines. D)RNA, protein, and lipids. E)a sugar, a phosphate, and a nitrogen-containing base. 5) In the Watson-Crick model of DNA, the "sides" of the ladder are composed of A sugars. Bbases. C)hydrogen bonds. D)sugar-phosphate molecules. E)phosphate groups. 6) Which of the following statements about DNA replication is correct? A)As hydrogen bonds break, the DNA molecule unwinds. B)The process is known as semiconservative replication because one old strand is conserved in the new molecule. C)The enzyme that catalyzes DNA replication is DNA polymerase. D)Complementary base pairs are held together with hydrogen bonds. E)All of the answer choices are correct statements about DNA replication,

Answer 1

3) According to Chargaff rule: Equimolar concentration of A=T and G=C Now if A=23%, therefore T=23%, A+T=23+23=46%, thus, G+C=( 100-46)%=54%, so amount of Guanine and cytosine is  (54/2)=27% each, so the percentage of Guanine it would contain is 27%.

4) Nucleotides are a group of small complex molecules forming a part of the information transform system. A nucleotide contains a cyclic nitrogenous base (Adenine, Guanine, Cytosine, thymine and uracil), sugars (ribose and deoxyribose) and a phosphate. So the correct option is (E).

5) In the Watson-Crick model of DNA, the "sides" of the ladder are composed of sugar and phosphate. This forms the backbone of the two strands of DNA. So the correct option is (D).

6) DNA replication is the process of producing two identical replicas of DNA from one parental DNA molecule. It involves four major steps which includes (a) Initiation of DNA replication, (b) Unwinding of helix, (c) Formation of primer strand and (d) Elongation of new strand. DNA replication requires that the double helical parental molecule is unwound so that its internal bases are available for replication. Unwinding is brought by enzyme Helicase with the dissociation of hydrogen bonds. The process of DNA replication is semi-conservative in nature as the new daughter DNA molecules formed made of one old or parental strand and another newly formed complementary strand. The enzyme that catalyzes DNA replication is DNA-dependent DNA polymerase which is the main enzyme of the said process. It is highly efficient and can able to polymerise 2000 bp per second. Complementary base pairs of the two polynucleotide strands are held together with hydrogen bonds. Adenine and thymine form two hydrogen bonds whereas Guanine and cytosine form three hydrogen bonds. So, all the answer choices are correct statements about DNA replication. Option (E) is the correct one.