The tail of a comet usually faces A) toward the Sun. B) away from the Sun C) toward the Earth. D) away from the Earth.

The outer cells of a blastocyst become the, an organ that offers protection and nourishment.

Photon energy is proportional to which of the following? A. period of the light wave B. frequency of the light wave C. speed of the light wave D. color of the light wave

Why is DNA replication necessary before each cell division?

Which is false? a. Enzymes are very specific for certain substrates. b. Enzymes are used up in chemical reactions. c. An enzyme binds to its substrate at the enzyme's active site. d. Enzymes emerge unchanged from the reactions they catalyze.

Human eggs and sperm each contain 23 chromosomes. Explain the significance of this during fertilisation in terms of chromosome numbers.

Immune privileged sites, such as the brain, the eye, and the testis, are often the targets of autoimmune attack.

How does the size of lactobacillus compared with that of oscillatoria and gloeocapsa?

g A polypeptide has the following amino acid sequence: Met-Ala-Gln-Arg-Glu-Leu. This polypeptide was mutated to produce the following mutant sequence: Met-Ala - Gln-Gly-Glu-Leu.

Where is a trench formed

Which statement best describes an operon? a. several genes, next to each other in eukaryotic DNA, that are transcribed as a single piece of mRNA b. a single gene in prokaryotic DNA that is transcribed as a single piece of mRNA c.