You are running a human assisted reproduction clinic and providing state-of-the-art genetic diagnostic services. A married couple who already had a child with cystic fibrosis approach you because they wish to have another child, but only if they can be assured that the child will not have cystic fibrosis. You genotype the woman and discover that she is a heterozygote for Del508, the most common mutation causing cystic fibrosis. You suggest that the couple consider first polar body testing, in which several unfertilized oocytes (each with its first polar body) are retrieved from the woman, the first polar bodies are removed, and PCR tests are conducted on DNA from each of the first polar bodies. The couple agrees, and you obtain the following results:

 

the observation that the polar bodies for oocytes #1 and #5 test positive for both Del508 and the wild type sequence, because

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#Question id: 13204

#Unit 6. System Physiology – Plant

Many of the carriers of Sucrose–H+ symporters in the phloem play various role in transport, most of the transporters are found in source, path, and sink tissues. Some carriers are characterized such as;

a) SUT1, has high-affinity / low-capacity transporter found in the minor veins of source tissues, appears to be important in phloem loading.

b) Important role of SUT1 in phloem loading appears to be complemented by SUT4, which is low-affinity/high-capacity carrier

c) SUT2, appears to function as a sucrose sensor. This is indicated by findings showing that SUT2 is more highly expressed in sink and path tissues than in source leaves.

d) The major sucrose transporters in phloem loading into the companion cells and final uptake into companion cells appears to be the function of SUT4

Which of the following combination is correct?

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#Question id: 13205

#Unit 6. System Physiology – Plant

The mechanisms that regulate the loading of sucrose from the apoplast to the sieve elements by the sucrose–H+ symporter await characterization. Possible regulatory factors include the following:

a) The solute potential or, more likely, the turgor pressure of the sieve elements

b) Sucrose concentration in the apoplast

c) The available number of symporter protein molecules

Which one of the mechanism that involve to regulate the loading of sucrose?

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#Question id: 13206

#Unit 6. System Physiology – Plant

Given below are some of the statements that regulate the sucrose loading mechanism;

A) The solute potential or, more likely, the turgor pressure of the sieve elements

B) Sucrose concentration in the apoplast

C) The available number of symporter protein molecules

Possible observation given on how to avoid regulation;

i) increase in sieve element turgor above a certain threshold would lead to a compensatory increase in loading

ii) High sucrose concentrations in the apoplast would increase phloem loading

iii) SUT1 transporter mRNA and protein have been lower after 15 hours of darkness than after a light treatment. These data suggest that the concentration of SUT1 transporter molecules could regulate loading

iv) Decrease in sieve element turgor below a certain threshold would lead to a compensatory increase in loading

v) The transporter mRNA and protein high in darkness than lower in the light treatment

Which of the following combinations represents correct observation?

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#Question id: 13207

#Unit 6. System Physiology – Plant

The polymer-trapping model explains symplastic loading in plants with intermediary-type companion cells, this model makes three prediction; which one of the following prediction is INCORRECT?

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#Question id: 13208

#Unit 6. System Physiology – Plant

The polymer trapping model explains that, Plasmodesmata between the  Bundle sheath cell  and intermediary cells must be smaller that allows only selective sugar to diffuse from this Plasmodesmata such as;

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#Question id: 13209

#Unit 6. System Physiology – Plant

After unloading, the sugars are transported to cells in the sink by means of a short-distance transport pathway. This pathway has also been called,