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TLS Online TPP Program

#Question id: 2858

When lactose enters the cell, it is converted to allolactose. It is allolactose (rather than lactose itself) that controls the Lac repressor. Paradoxically, the conversion of lactose to allolactose is catalyzed by b-galactosidase, itself encoded by one of the lac genes. How is this possible? Which statement is incorrect according lac genes expressions?

#Unit 2. Cellular Organization

  1. The expression of the lac genes is leaky, even when they are repressed, because, allolactose binds to a part of the Lac repressor distinct from its DNA-binding domain.

  2. In the absence of allolactose, the repressor is present in a form that binds its site on DNA (and so keeps the lac genes switched off).

  3. Allolactose has altered the shape of the repressor, the protein can no longer bind DNA, and so the lac genes are no longer repressed.

  4. This leakiness ensures that there is a low level of b-galactosidase in the cell even in the absence of glucose, and so there is enzyme poised to catalyze the conversion of lactose to allolactose.

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TLS Online TPP Program

#Question id: 4857

#Unit 8. Inheritance Biology

Sturtevant provided genetic evidence for the existence of four pairs of chromosomes in Drosophila in which of these ways?
TLS Online TPP Program

#Question id: 4858

#Unit 8. Inheritance Biology

Which of the following statements is true?
TLS Online TPP Program

#Question id: 4859

#Unit 8. Inheritance Biology

How would one explain a testcross involving F1 dihybrid flies in which more parental-type offspring than recombinant-type offspring are produced?
TLS Online TPP Program

#Question id: 4860

#Unit 8. Inheritance Biology

 A plant of genotype GGHH is crossed with another plant of the genotype gghh. If the F1 is test crossed, what percentage (%) of the test cross progeny will have the genotype gghh when the two genes are - (P) unlinked, (Q) completely linked with no crossing over, (R) 10 m.u. (genetic map unit) apart, (S) 24 m.u. apart?
TLS Online TPP Program

#Question id: 4861

#Unit 8. Inheritance Biology

Two character X and Y, both follow law of dominance due to 3:1 F2 phenotypic ratio monohybrid cross separately. If carry out dihybrid selfing cross for heterozygous genotype for both character does not follow law of independence assortment in normal environmental condition due to  these two loci for character are linked at 20 map unit as cis configuration. Which of the following proportional genotype that homozygous for all loci in F2 generation?
TLS Online TPP Program

#Question id: 4862

#Unit 8. Inheritance Biology

In guinea pigs, white coat (w) is recessive to black coat (W) and wavy hair (v) is recessive to straight hair (V). A breeder crosses a guinea pig that is homozygous for white coat and wavy hair with a guinea pig that is black with straight hair. The F1 are then crossed with guinea pigs having white coats and wavy hair in a series of testcrosses. The following progeny are produced from these testcrosses:

black, straight  -   220             black, wavy  -30

white, straight  -30                   white, wavy- 220

If the genes are not assorting independently, what is the distance between coat color and hair shape governing gene