Which of the following is the unit of contraction in a skeletal muscle cell?
a. Myofibril
b. Myosin
c. Actin filament
d. Sarcomere
d. Sarcomere
The sarcomere is the unit of contraction in a skeletal muscle cell. They are stimulated by an electrochemical signal from a nerve cell associated with the muscle fiber.
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The methylation and demethylation of regions
of DNA triggered by changes in the environment and resulting in phenotypic changes are an example of
a. pleiotropy. b. environmental effects. c. epistasis d. epigenesis. e. more than one of these
What discoveries in the fossil record led to
questioning the concept that species didn’t change?
a. the oldest layers contain fossils of simpler organisms b. more recent layers contain fossils more similar to existing species c. many fossils were found of extinct animals d. more recent layers contain fossils that are more complex than earlier ones e. all of these are discoveries in the fossil record that led to questioning the concept that species didn’t change
Which situation demonstrates only the genetic influence on a trait?
A) Hair dye turns Angela's brown hair to red. B) Sandy's hair becomes blonder when she spends time out in the sun. C) Jen has brown hair, just like her mother and father. D) Identical twins Kiera and Tanya have different colored hair.
Chemotaxis is made possible by help of:
A. Pili B. Cilia C. Quorum sensing D. Flagella