Following statements are regarding to the early development in sea urchin.

A. most cells of the 16-cell embryo, the large micromeres are autonomously specified.

B. large micromeres inherit maternal determinants that were deposited at the vegetal pole of the egg; these become incorporated into the large micromeres at the fourth cleavage.

C. The conditionally specified large micromeres are now able to produce paracrine and juxtacrine factors that autonomously specify the fates of their neighbors.

D. Large micromeres become skeletogenic mesenchyme cells that will leave the blastula epithelium, enter the blastocoel, migrate to particular positions along the blastocoel wall, and then differentiate into the larval skeleton.

Which of the following statement is false?

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#Question id: 15658

#Unit 13. Methods in Biology

You are studying a new strain of E. coli that can utilize the disaccharide melibiose very efficiently. You find that utilization depends on the enzyme melibiase, which is encoded by the gene Mel1. Mel1 is not expressed unless melibiose is present in the growth medium.

Next, you isolate a third mutant, MelC–, which gives constitutive melibiase expression. The MelC– mutation is closely linked to Mel1 and MelB–. Genetic tests of the MelC– mutation yield the following:

 

As above, classify the MelC– mutation in terms of its basic genetic properties and explain how you arrived at your conclusions.

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#Question id: 15659

#Unit 8. Inheritance Biology

You calculate map distances between genes A, B, and C based on all pairwise dihybrid crosses. When you perform the trihybrid cross to verify your results, you discover that, despite analysis of a very large number of progeny, you have only about half as many double crossover progeny as you expect. Which explanation is the most reasonable?

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#Question id: 15660

#Unit 8. Inheritance Biology

Tetrad analysis automatically includes the centromere as an additional point in mapping crosses, because

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#Question id: 15661

#Unit 8. Inheritance Biology

Which of the following is NOT true of a maternal effect gene?

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#Question id: 15662

#Unit 8. Inheritance Biology

You develop an inbred strain of mice that display one of two distinct syndromes. What evidence might lead you to believe that these mice are mutant for a gene or genes affected by imprinting?

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#Question id: 15663

#Unit 8. Inheritance Biology

A mouse heterozygous at the Igf-2 locus is dwarf and has 50% dwarf progeny when mated to a homozygous Igf-2m animal. Which statement about this animal is FALSE?