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TLS Online TPP Program

#Question id: 16147

 Which statement is not true for Natural killer (NK) cells?

#Unit 4. Cell Communication and Cell Signaling
  1. Natural killer (NK) cells are lymphoid cells that are closely related to B and T cells. However, they do not express antigen specific receptors and are considered part of the innate immune system.
  2. They are distinguished by the expression of a surface marker known as NK1.1, as well as the presence of cytotoxic granules. Once referred to as “large granular lymphocytes” because of their appearance under a microscope.
  3.  NK cells constitute 5% to 10% of lymphocytes in human peripheral blood. Th ey are effi cient cell killers and attack a variety of abnormal cells, including some tumor cells and some cells infected with virus.
  4. They distinguish cells that should be killed from normal cells in a very clever way: by “recognizing” the absence of MHC class II, which is expressed by almost all normal cells, but is specifically down-regulated by some tumors and in response to some viral infections.
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TLS Online TPP Program

#Question id: 7283

#Unit 5. Developmental Biology

The Drosophila orthodenticle gene and the vertebrate Otx genes are homologous and provide a good example of the conservation of gene function during evolution. Which of the following statement is correct regarding to the expression of gene expression.
TLS Online TPP Program

#Question id: 7282

#Unit 5. Developmental Biology

In humans, neural tube closure defects occur in about 1 in every 1000 live births. Failure to close the neural tube can result from both genetic and environmental causes. A recent report has demonstrated that zinc deficiency disrupts neural tube closure by:
TLS Online TPP Program

#Question id: 7281

#Unit 5. Developmental Biology

Evolutionary conservation of homeotic gene organization and transcriptional expression in fruit flies and mice is seen in the similarity between the Hom-C cluster on Drosophila chromosome 3 and the four Hox gene clusters in the mouse genome.

 

According to this figure, Which of the following statement is correct?
TLS Online TPP Program

#Question id: 7280

#Unit 5. Developmental Biology

In drosophila, Physical forces drive invagination of the ventral furrow. Following statements regarding to this process:

A. The cellularized blastoderm will begin to activate higher levels of myosin in the cells at the ventral midline and preferentially at their apical surface.

B. Epithelial adhesions paired with differential activation of dynein and tissue geometry create mechanical constraints that affect the orientation of actomyosin meshworks.

C. The A/P oriented arrays of myosin in the cells at the ventral midline generate tension along the anterior-posterior axis.

D. The combination of tissue geometry and tension of these anterior-to-posterior meshworks cause the tissue to fold outward at a right angle to the anterior-posterior axis, creating a long and narrow ventral furrow.

Which of the following statements are incorrect?
TLS Online TPP Program

#Question id: 7279

#Unit 5. Developmental Biology

X chromosome number alone is the primary sex determinant in normal drosophila because:
TLS Online TPP Program

#Question id: 7278

#Unit 5. Developmental Biology

The following demonstrates the blastocoel formation in the mammals. Which of the following statement is correct?