Which of the following would be the last form of prezygotic barrier that could take place in maintaining reproductive isolation between two individuals?
a. Mechanical isolation
b. Hybrid breakdown
c. Gametic isolation
d. Habitat isolation
e. Behavioral isolation
Answer: c. Gametic isolation
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The selection and differentiation of B cells during clonal selection is an example of:
A. mitosis. B. meiosis. C. binary fission. D. cytokinesis.
In response to injury, cell fragments called platelets get activated to induce clotting. Activated platelets release factors that can in turn bind to specific membrane receptors on nearby cells. What type of signaling would this be considered?
A. Direct contact B. Paracrine C. Endocrine D. Synaptic E. Autocrine
Imagine that horn color in Hodags (folkloric creatures of Wisconsin) is controlled by a single gene so that when you mate a Hodag homozygous for bright orange horns (COCO) with a Hodag homozygous for ivory horns (CICI), numerous offspring are produced, all with pale orange horns. Now consider that you cross an orange-horned Hodag with an ivory-horned Hodag and get an F1.
A. 9 bright orange: 6 pale orange: 1 ivory B. 1 bright orange: 2 pale orange: 1 ivory C. 3 bright orange: 1 ivory D. 1COCO: 2COCI: 1CICI E. 3COCO: 1CICI Clarify Question
Acetylation
a. adds an acetyl group (CH3CO?) to the cytosine nucleotides of DNA. b. adds an acetyl group (CH3CH2?) to the DNA of a promoter sequence. c. adds an acetyl group (CH3CO?) to the histone protecting the transcription unit of a gene. d. adds an acetyl group (CH3CO?) to the histone protecting the promoter region of a gene. e. adds an acetyl group (CH3CH2?) to the RNA polymerase that will initiate transcription at the promoter region.