A defect in the absorption of certain nutrients in the small intestine has been linked to an abnormally-delayed initiation of differentiation. If the levels of HER2, PTEN, and Akt protein can be estimated accurately, what is the earliest point in development at which the defect could be evaluated?a. 14 weeks. b. 16 weeks. c. 20 weeks. d. 24 weeks.

B. 16 weeks

Explanation:

It has been observed that a defect in the absorption of certain nutrients in the small intestine has shown to be linked to an abnormally-delayed initiation of differentiation of the cells of the small intestines.

Factors responsible for differentition of cells.

1. HER2 (Human epidermal growth factor receptor 2). It is a gene that makes a protein found on the surface of all breast cells. It is involved in normal cell growth.

However in certain cancers, especially breast cancer, the HER2 gene mutates (changes) and makes extra copies of the gene. When this happens, the HER2 gene makes too much HER2 protein, causing cells to divide and grow too fast.

Cancers with high levels of the HER2 protein are known as HER2-positive. Cancers with low levels of the protein are known as HER2-negative. About 20 percent of breast cancers are HER2-positive.

HER2 testing looks at a sample of tumor tissue. The most common ways to test tumor tissue are:

i. Immunohistochemistry (IHC) testing measures the HER2 protein on the surface of the cells

ii. Fluorescence in situ hybridization (FISH) testing looks for extra copies of the HER2 gene

Both types of tests can tell whether the patient have HER2-positive cancer. Treatments that specifically target HER2-positive breast cancer can be very effective.

2. Phosphatase and tensin homolog (PTEN) is a protein found in humans, encoded by the PTEN gene. PTEN also acts as a tumor suppressor gene through the action of its phosphatase protein product. This phosphatase is involved in the regulation of the cell cycle, preventing cells from growing and dividing too rapidly. It is a target of many anticancer drugs.

The protein encoded by this gene is a phosphatidylinositol-3,4,5-trisphosphate 3-phosphatase. It contains a tensin-like domain as well as a catalytic domain similar to that of the dual specificity protein tyrosine phosphatases. Unlike most of the protein tyrosine phosphatases, this protein specifically dephosphorylates phosphoinositide substrates. It negatively regulates intracellular levels of phosphatidylinositol-3,4,5-trisphosphate in cells and functions as a tumor suppressor by negatively regulating Akt/PKB signaling pathway.

3. AKT1 gene/protein encodes an enzyme in humans called RAC-alpha serine/threonine-protein kinase.

So when this levels of HER2, PTEN, and Akt protein are estimated accurately within 16 weeks, the defect in the absorption of certain nutrients in the small intestine can be detected.

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