Question

How are purines different from pyrimidines?

		Pyrimidines form hydgrogen bonds, while purines form phosphodiester bonds
		Purines are only found in DNA, pyrimidines are only found in RNA
		Pyrimidines use deoxyribose as a sugar, while purines use ribose
		Pyrimidines have a single ring of carbons, while purines have two

The following two bacteria are crossed:

Hfr amp^s arg⁺ bio^- leu⁺X F^- amp^R arg^- bio⁺ leu^-

Assuming the order of the genes is as shown above, which of the following recombinants would be expected be expected to be LEAST abundant from this cross?

		F- ampR arg+ bio+ leu+
		F- ampR arg+ bio- leu+
		F- ampR arg+ bio+ leu-
		F- ampR arg+ bio- leu-

Answer 1

Solution of 1st Question:-The correct option will be "Pyrimidines have a single ring of carbons, while purines have two".

Explanation:-Pyrimidines Contains one carbon-nitrogen ring and two nitrogen atoms while purines contains two carbon-nitrogen rings and four nitrogen atoms.

Solution of 2nd Question:- The correct option will be F^- ampR arg+ bio-leu⁺

Explanation:- We see that the above genotype matches the genotype of one of the parents. Since recombination indicates a mix of the parental genes, this strain will be the least likely to be seen.