Given a context passage, generate a question from the passage such that its answer is shortest continous span from the passage.
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Question: Pancreatic ductal adenocarcinoma (PDAC) is one of the most lethal cancers worldwide. Despite significant progresses in the last decades, the origin of this cancer remains unclear and no efficient therapy exists. PDAC does not arise de novo: three remarkable different types of pancreatic lesions can evolve towards pancreatic cancer. These precursor lesions include: Pancreatic intraepithelial neoplasia (PanIN) that are microscopic lesions of the pancreas, Intraductal Papillary Mucinous Neoplasms (IPMN) and Mucinous Cystic Neoplasms (MCN) that are both macroscopic lesions. However, the cellular origin of these lesions is still a matter of debate. Classically, neoplasm initiation or progression is driven by several genetic and epigenetic alterations. The aim of this review is to assemble the current information on genetic mutations and epigenetic disorders that affect genes during pancreatic carcinogenesis. We will further discuss the interest of the genetic and epigenetic alterations for the diagnosis and prognosis of PDAC. Large genetic alterations (chromosomal deletion/amplification) and single point mutations are well described for carcinogenesis inducers. Mutations classically occur within key regions of the genome. Consequences are various and include activation of mitogenic pathways or silencing of apoptotic processes. Alterations of K-RAS, P16 and DPC4 genes are frequently observed in PDAC samples and have been described to arise gradually during carcinogenesis. DNA methylation is an epigenetic process involved in imprinting and X chromosome inactivation. Alteration of DNA methylation patterns leads to deregulation of gene expression, in the absence of mutation. Both genetic and epigenetic events influence genes and non-coding RNA expression, with dramatic effects on proliferation, survival and invasion. Besides improvement in our fundamental understanding of PDAC development, highlighting the molecular alterations that occur in pancreatic carcinogenesis could provide new clinical tools for early diagnosis of PDAC and the molecular basis for the development of new effective therapies.

Answer: Which is the molecular mechanism underlying K-ras alterations in carcinomas?


Question: In the county, the population was spread out with 23.20% under the age of 18, 7.70% from 18 to 24, 27.00% from 25 to 44, 28.00% from 45 to 64, and 14.10% who were 65 years of age or older. The median age was 40 years. For every 100 females, there were 97.00 males. For every 100 females age 18 and over, there were 96.40 males.

Answer: Which age group had the most people?


Question: In 2009, 78.5% of Dallas (city) commuters drive to work alone. The 2009 modal share for Dallas (city) commuters are 10.7% for carpooling, 3.9% for transit, 1.9% for walking, and .1% for cycling. In 2015, the American Community Survey estimated modal shares for Dallas (city) commuters of 75.4% for driving alone, 12.8% for carpooling, 3.5% for riding transit, 1.9% for walking, and .2% for cycling. The city of Dallas has a higher than average percentage of households without a car. In 2015, 10.2 percent of Dallas households lacked a car, and decreased to 9.1 percent in 2016. The national average was 8.7 percent in 2016. Dallas averaged 1.59 cars per household in 2016, compared to a national average of 1.8.

Answer:
Which group of commuters in 2009 was the largest in Dallas, carpooling or transit?