In this problem we will explore some of the many ways that mutations in two different genes can interact to produce different Mendelian ratios. Consider a hypothetical insect species that has red eyes. Imagine mutations in two different unlinked genes that can, in certain combinations, block the formation of red eye pigment yielding mutants with white eyes. In principle, there are two different possible arrangements for two biochemical steps responsible for the formation of red eye pigment. The two genes might act in series such that a mutation in either gene would block the formation of red pigment. Alternatively, the two genes could act in parallel such that mutations in both genes would be required to block the formation of red pigment.

Further complexity arises from the possibility that mutations in either gene that lead to a block in enzymatic activity could be either dominant or recessive. If the crosses is made between a wild type insect with red eyes and a true breeding white eyed strain with mutations in both genes. Such considerations yield the Pathways in series with recessive mutations in both genes, what will be the phenotype in F1 progeny?

#Question id: 2533

#Unit 2. Cellular Organization

Cellulose microfibrils have an ordered structure and are synthesized at the plasma membrane, given characteristics of microfibrils;

a) Each microfibril is composed of an estimated 18 parallel chains of (1,4)-linked β-D-glucose chains tightly bonded to each other to form a crystalline microfibril

b) Microfibrils have hydrophilic surfaces, populated by polar –OH groups extending from theplane of the sugar rings

c) Microfibrils have hydrophobic surfaces, populated by nonpolar C–H groups populating thesides of stacked glucose chains

 d) microfibril important for enzymatic attack by microbial cellulases, which dock onto the hydrophobic surface and remove one glucan chain at a time

Which of the following from given characterstics of microfibrils is incorrect?

#Question id: 2534

#Unit 2. Cellular Organization

How the matrix polysaccharides are differ from the cellulose?

#Question id: 2535

#Unit 2. Cellular Organization

Expansins belong to a large superfamily of proteins, divided into two major expansin families, α-expansins (EXPAs) and β-expansins (EXPBs), what is the function of these two?

a) EXPAs are more active on eudicot cell walls,whereas EXPBs are more active on grass cell walls

b) EXPAs are more active on grass cell walls, whereas EXPBs are more active on eudicot cell walls

c) EXPAs loosen cellulose–cellulose junctions containing xyloglucan, whereas EXPBs loosen wall complexes containing GAX

d) EXPAs loosen wall complexes containing GAX, whereas EXPBs loosen cellulose–cellulose junctions containing xyloglucan

Which combination is correct from some given above functions of expansins,?

#Question id: 2536

#Unit 2. Cellular Organization

If the cytoplasm of a cell is at pH 7, and the mitochondrial matrix is at pH 8, then the concentration of H+ ions ________.

#Question id: 2537

#Unit 2. Cellular Organization

Which of the following is the smallest structure that would most likely be visible with a standard (not super-resolution) research-grade light microscope?

#Question id: 2538

#Unit 2. Cellular Organization

Which of the following frequently imposes a limit on cell size?