A prenatal diagnosis procedure that has recently come into wide use and can be performed earlier than amniocentesis

involves sampling the _____.
a. yolk sac material
b. allantois
c. chorion
d. yolk sac
e. umbilical cord


ANSWER: c

Biology & Microbiology

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The common basilisk lizard will run across water on its hind legs in an erect position when startled by predators. This lizard has large feet and flaps of skin along its toes. What properties of water allow this lizard to walk on water?

A. Hydrogen bonds absorb heat when they break and release heat when they form. This helps to minimize temperature changes. B. The surface tension created by hydrogen bonds is greater than the weight of the lizard initially. C. Polar molecules are attracted to ions and polar compounds, making these compounds soluble. D. Hydrogen bonds hold water molecules together; many hydrogen bonds must be broken for water to evaporate.

Biology & Microbiology

Rolling circle replication of the lambda genome differs from replication of a bacterial chromosome in that

A) bidirectional replication forks are not formed. B) only a single strand of the genome is copied. C) no concatamers are formed. D) only a single strand of the genome is copied and no concatamers are formed.

Biology & Microbiology

Sponges are heavily preyed upon by marine fishes

Indicate whether the statement is true or false

Biology & Microbiology

The receptor potential is the

A) membrane potential produced when a neurotransmitter molecule binds to its receptor. B) membrane potential produced in the receptor cell by sensory transduction. C) electrical signal produced by an action potential. D) membrane potential produced at a muscle cell.

Biology & Microbiology