Question

Which of the following is an accurate statement regarding the relationship between primers and nucleic acid synthesis?

		During DNA replication, primers are used to initiate DNA synthesis, and these primers are incorporated into the final daughter strand products.
		During DNA replication, leading strands are synthesized by DNA polymerase III without utilizing a primer.
		During DNA replication, every Okazaki fragment synthesized by DNA polymerase III is elongated from a separate RNA primer.
		Primase catalyzes the de novo polymerization of DNA.

Thymine is used in DNA instead of uracil because:

		It allows for the detection and correction of the potentially mutation-causing spontaneous deamination of cytosine to uracil.
		uracil cannot form a base pair with adenine.
		Uridine mono phosphate (UMP) is not a substrate for ribonucleotide reductase.
		uracil prevents the binding of DNA polymerase III during mismatch repair.

		It is a sequence in the promoter region of genes that marks transcription start sites.
		It is a sequence in chromosomes that marks replication origins.
		It is a sequence in primary transcripts that marks cleavage and polyadenylation sites.
		It is a sequence in mRNAs that marks translation start sites.

Which of the following enzymes catalyzes a highly regulated step involved in both amino acid synthesis and amino acid degradation?

	Alanine aminotransferase
		Aspartate aminotransferase
		Glutamate dehydrogenase
		Glutamine synthetase
		None of the above

Which of these directly donates amino groups into the urea cycle for incorporation into and disposal as urea?

		aspartate
		glutamate
		glutamine
		ornithine

Answer 1

1. Answer: Option C is correct
Explanation:
A primer is a short oligonucleotide sequence that provides a free 3'-OH group for the strand extension.
RNA primers are synthesized during DNA replication. These primers are later replaced by DNA polymerase.
The leading strand requires a single primer.
The leading strand requires multiple primers i.e. each Okazaki fragment requires a single primer.

2. Answer: Option A is correct
Explanation:
The spontaneous deamination of Cytosine produces Uracil.
If DNA contains Uracil, the repair systems would not able to distinguish whether C is mutated to U or the complementary base G is misincorporated.