Ch 16 Q 1 Tumor cells are considered to be malignant if A th

Ch 16 Q.

Solution

1. Uncontrolled proliferation of cells leads to tumour formation . They can be benign or malignant . Benign tumour are harmless as they don\'t invade other tissues , where as Malignant tumour are harmful as they invade other tissues and spread throughout the body. Hence the correct answer is option B.

2. The estimate regarding small role of environmental factor contributing towards cancer is out dated . Today as per study smoking and diet alone are cause of 60 % of cancer deaths in America.

Hence the correct answer is option D.

3. As per Knudson\'s hypothesis mutation of both the alleles of a gene is required. Some times both the alleles are mutated sequentially leading to tumour after birth which is the case in sporadic cancer. While some times one of alleles is mutated by birth and needs only one mutation to cause tumour . This is the case of inherited cancer. And usually cancer develops in both the eyes .

Hence the correct answer is option D.