How does crossing-over result in genetic recombination? A. It reduces the original cell’s chromosome number by half.

B. It mixes half the maternal chromosomes with half the paternal chromosomes.

C. It randomly separates the maternal and paternal chromosomes.

D. It permits the exchange of genetic material between homologous chromosomes.

Which part of cellular respiration must occur before any of the other steps can occur

How is ribosomal rna useful as a molecular clock? a. a large portion of the dna ring is not vital to structure or function, allowing it to accumulate neutral mutations. b. its rate of mutation increases over time as organisms continue to evolve and differentiate from each other. c. a slow mutation rate makes it useful for determining evolutionary relationships between ancient species. d. it is only found in select organisms, making it easier to compare relationships between species that have it.

When you run, you begin to breathe heavier and faster. your heart beats more quickly, bringing more oxygen to your cells. which organ systems are working together here?