The probability that a child will inherit a mutant allele from each carrier parent is equal to p1 x p2 =1/4 because these are independent events (Choices A, B, and D).
(Choice C) The probability of having two future children both inherit an autosomal recessive disease from parents who are heterozygous carriers is 1/4 x 1/4 = 1/16 (each 1/4 representing the likelihood of 1 child inheriting the disease). In this case, this family already has an affected child, making the probability of a single subsequent child with the disease remain at 1/4.
(Choice F) The probability that a child will inherit an autosomal dominant disorder if one parent is affected is 1/2.

(Choice A) Eukaryotic and prokaryotic DNA polymerases synthesize daughter strand DNA in the 5′ to 3′ direction. The leading strand is formed continuously, whereas the lagging strand is formed discontinuously, creating Okazaki fragments.
(Choice B) DNA unwinding is an energy-dependent process performed by the enzyme helicase in both prokaryotes and eukaryotes.
(Choice D) Proofreading of daughter strands during DNA replication is necessary to preserve the genetic code and prevent potentially lethal mutations. All 3 prokaryotic DNA polymerases and most eukaryotic DNA polymerases (eg, y, o, E) possess 3′ to 5′ exonuclease (“proofreading”) activity.
(Choice E) Prokaryotic and eukaryotic DNA polymerases require an RNA primer before they can initiate synthesis of complementary DNA on a single-stranded template. Primase (prokaryotes) and DNA polymerase a (eukaryotes) are the enzymes responsible for synthesizing this primer.

(Choices A and F) The non-essential glucogenic amino acids alanine and serine can be converted to pyruvate through a transamination reaction catalyzed by alanine transaminase and a deamination reaction catalyzed by serine dehydratase, respectively.
(Choice B) Asparagine is catabolized to aspartate and subsequently transaminated to produce glutamate and oxaloacetate, an intermediate of the TCA cycle. Oxaloacetate by itself cannot be used to produce energy; it must first undergo condensation with acetyl-CoA to form citrate.
(Choice C) The monosaccharide galactose is metabolized in the glycolytic pathway; dietary intake will result in elevated levels of lactate in patients with pyruvate dehydrogenase deficiency.
(Choice D) Glycerol is metabolized to glyceraldehyde 3-phosphate, a glycolysis intermediate. It can be used as a substrate to form pyruvate and, subsequently, lactate.