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 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 parallel with a recessive mutation in one gene and a dominant mutation in the other, determine the phenotype of the F1 progeny and the expected phenotypic ratio of red to white eyed insects in the F2.

#Question id: 10347

#Unit 6. System Physiology – Plant

NH4+ is toxic to plants, inhibit dinitrogenase and also interfere energy metabolism by dissociating ATP formation  from ETC  in both mitochondria and chloroplasts. What will plant cells do to avoid this problem?

a) Plant cells avoid ammonium toxicity by rapidly converting the ammonium generated from nitrate assimilation or photorespiration into nitrate

b) Plant cells avoid ammonium toxicity by rapidly converting the ammonium generated from nitrate assimilation or photorespiration into amino acids

c) The pathway for this conversion involves the sequential actions of glutamine synthetase (GS) and glutamate synthase (GOGAT)

d) The pathway for this conversion involves the sequential actions of Aspartate aminotransferase (Asp-AT) and Asparagine synthetase (AS)

Which of the above statements is incorrect?

#Question id: 10346

#Unit 6. System Physiology – Plant

Nitrite reductase will convert nitrite to ammonium. There are two types of nitrite reductase characteristics given below;

a) Both nitrite reductase consist of a single 63kD polypeptide

b) In leaf chloroplasts and root plastids contain different forms of the nitrite reductase enzyme

c) In shoot nitrite reductase directly dependent on the light reaction by the ferredoxin, it activates nitrite reductase in choloroplast

d) NADPH in the roots is provided by pentose phosphate pathway, it also activate nitrite reductase in the plastids

Which of the correct statement about nitrite reductase characteristics?

#Question id: 10345

#Unit 6. System Physiology – Plant

In Leaf Chloroplasts and root plastids contain different forms of the enzyme, nitrite reductase such as

a) Roots contain fd-dependent nitrite reductase

b) Shoots contain NADPH dependent nitrite reductase

c) Shoots contain fd-dependent nitrite reductase

d) Roots contain NADPH dependent nitrite reductase

Which one of the following is correct combination?

#Question id: 10344

#Unit 6. System Physiology – Plant

Some of the following caracteristics of Nitrite reductase, which one of the is incorrect?

#Question id: 10342

#Unit 6. System Physiology – Plant

Nitrate reductase is an important enzyme for nitrate assimilation. Given below some regulation of nitrate reductase activity through phosphorylation and dephosphorylation.

a) Light, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby activates the enzyme

b) In Dark, and Mg2+ stimulate a protein kinase that phosphorylates the same serine residues, which then interact with a 14-3-3 inhibitor protein, and thereby inactivate nitrate reductase

c) In Light, and Mg2+ stimulate a protein kinase that phosphorylates the serine residues, and thereby activate nitrate reductase

d) In Dark, and other environmental factors stimulate a protein phosphatase that dephosphorylates a key serine residue in the hinge 1 region of nitrate reductase and thereby inactivates the enzyme

Which of the following statements about regulation of nitrate reductase is correct?

#Question id: 10339

#Unit 6. System Physiology – Plant

Nitrate assimilates into the root where the conversion of nitrate to nitrite in the cytosol, a reduction reaction that involves the transfer of two electrons catalyzes by an enzyme that is NAD(P)H dependent is known as