Proper division of chromosomes fails more frequently in mammalian oogenesis than in mammalian spermatogenesis. What is the most likely reason for this phenomenon? a. Crossover events occur in oogenesis but do not occur in spermatogenesis.
b. Oogenesis creates polar bodies, whereas spermatogenesis does not.
c. Primary oocytes are haploid, whereas primary spermatocytes are diploid.
d. Oogenesis is arrested in prophase I, whereas spermatogenesis is not arrested.

Mouse liver cells were homogenized and the homogenate subjected to equilibrium density-gradient centrifugation with sucrose gradients. fractions obtained from these gradients were assayed for marker molecules (i.e., molecules that are limited to specific organelles). the results of these assays are shown in the figure. the marker molecules have the following functions: cytochrome oxidase is an enzyme involved in the process by which atp is formed in the complete aerobic degradation of glucose or fatty acids; ribosomal rna forms part of the protein-synthesizing ribosomes; catalase catalyzes decomposition of hydrogen peroxide; acid phosphatase hydrolysis monophosphoric esters at acid ph; cytidylyltransferase is involved in phospholipid biosynthesis; and amino acid permease aids in transport of amino acids across membranes. a) name the marker molecule and give the number of the fraction that is most enriched for each of the following cell components: lysosomes; peroxisomes; mitochondria; plasma membrane; rough endoplasmic reticulum; smooth endoplasmic reticulum.

Which statement best describes lactic acid fermentation? a. lactic acid fermentation is the first step of cellular respiration. o b. lactic acid fermentation is the final step of cellular respiration. re to berate c. in the absence of oxygen, cells release atp by breaking down lactose into glucose. e der lade res o d. in the absence of oxygen, cells release atp by breaking down glucose into lactate. ar

Which of these substances does not protect against invaders in the nonspecific immune response? a. saliva b. mucus c. tears d. urine