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 parallel with recessive mutations in both genes, determine the phenotype of the F1 progeny and the expected phenotypic ratio of red to white eyed insects in the F2.

#Question id: 10902

#Unit 6. System Physiology – Plant

P-proteins from the genus Cucurbita consist of two major proteins: PP1, the phloem filament protein, and PP2, the phloem lectin. Both PP1 and PP2 are thought to be synthesized in_______A___________and transported via the_______B_________to the_______C______, where they associate to form P-protein filaments and P-protein bodies.

#Question id: 10903

#Unit 6. System Physiology – Plant

Materials translocated in the phloem, such as sucrose, amino acids, hormones and some inorganic ions. Some inorganic solutes that move in the phloem called mobile elements. In contrast, some are relatively immobile in the phloem.

A) Immobile elements

B) Mobile elements

i) potassium, magnesium, phosphate, and chloride

ii) caesium, zinc, magnesium and iron

iii) nitrate, calcium, sulfur, and iron

iv) potassium, calcium, cobalt and caesium

Which of the following are the correct match of mobile and immobile elements in the phloem?

#Question id: 10904

#Unit 6. System Physiology – Plant

The sugar is a carbohydrate that are generally translocated  in the phloem in which form?

#Question id: 10905

#Unit 6. System Physiology – Plant

The rate of movement of materials in the sieve elements can be expressed in two ways: as velocity, or as mass transfer rate. In early publications reporting on rates of transport in the phloem, what is the velocity and the mass transfer rate?

i) velocity-centimeters per hour (cm h^-1) and mass transfer- grams per hour per square centimeter (g h^-1 cm^-2)

ii) velocity-the linear distance traveled per unit time and mass transfer rate-the quantity of material passing through a given cross section of phloem or sieve elements per unit time.

iii) velocity- the quantity of material passing through a given cross section of phloem or sieve elements per unit time and mass transfer rate- the linear distance traveled per unit time

iv) velocity- per hour per square centimeter (h^-1 cm^-2) and mass transfer- kg centimeters per hour (cm h^-1)

#Question id: 10906

#Unit 6. System Physiology – Plant

The pressure-flow model explains phloem translocation as a flow of solution (bulk flow) driven by an osmotically generated pressure gradient between source and sink.

a) Phloem translocation, both active and passive mechanisms were considered. All theories, both active and passive, assume an energy requirement in both sources and sinks.

b) In sources, energy is necessary to move photosynthate from producing cells into the sieve elements. This movement of photosynthate is called phloem loading.

c) In sinks, energy is essential for some aspects of movement from sieve elements to sink cells, which store or metabolize the sugar. This movement of photosynthate from sieve elements to sink cells is called phloem unloading.

d) The Active mechanisms of phloem transport further assume that energy is required in the sieve elements of the path between sources and sinks simply to maintain structures.

From the given statements find out the correct for pressure-flow model.

#Question id: 10907

#Unit 6. System Physiology – Plant

The mechanism of phloem translocation in angiosperms is best explained by the pressure-flow model, this model is an example of,