How did evolutionary changes cause the loss of forelimbs in snakes?
What will be an ideal response?
Most snakes lack limbs. However, they have Hoxc6 and Hoxc8 genes that are associated with the
formation of limb buds and forelimbs, but their expression suppresses the development of limb buds
and forelimbs because of where they are found. Therefore, the spatial patterns of gene expression
caused the loss of forelimbs in snakes.
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The receptors on T cells and B cells bind to _____
A) antibodies B) antigens C) natural killer cells D) double-stranded RNA E) immunoglobulins
Which of the following are the mechanoreceptors that detect motion and sense gravity?
A. baroreceptors B. stereocilia C. hair cells D. semicircular canals
Imagine that you have two people using breathing gear under water. Diver 1 is using an old style "rebreather" that removes carbon dioxide before the mixture is "rebreathed" and therefore decreases overall carbon dioxide concentrations in the blood. Diver 2 is using regular SCUBA gear and is breathing air with the normal amount of carbon dioxide that does not lower blood levels of carbon dioxide. Which diver would have a higher blood pH and which would feel more an "urge to breathe"?
A. Diver 1 would have higher blood pH and would feel the "urge to breathe" sooner. B. Diver 2 would have higher blood pH and feel the "urge to breathe" sooner. C. Diver 1 would have higher blood pH, while Diver 2 would feel the "urge to breathe" sooner. D. Diver 2 would have higher blood pH, while Diver 1 would feel the "urge to breathe" sooner. E. There would be no difference in blood pH or breathing between the two divers.
In crossing a homozygous recessive with a heterozygote, what is the chance of getting a homozygous recessive phenotype in the F1 generation?
A) 75% B) 50% C) 25% D) 100% E) 0%