Question

Which of the folloving examples is likely to be caused by a somatic mutation? A. A purple flower has a small patch of white tissue. B. One child, in a famsily of seven, is an albino. C One apple tree, in a very large orchart, poduces its apples 2 weeks earlier than any of the other trees. D. A 60 -year-old smoker develops lung cancer.

Short answer

The most likely example of a somatic mutation from these cases is D. A 60-year-old smoker develops lung cancer.

Step-by-step solution

Rule Out Germline Mutation Cases

Observe each case and eliminate those where the change can be inherited, as these are likely due to germline mutations. Case B describes one child in a family being an albino which is likely due to a germline mutation, so it can be ruled out.

Look for Somatic Mutation Cases

Among the remaining cases, identify the one(s) that could be caused by changes to a cell's DNA after conception. The case of the purple flower with a patch of white tissue (Case A) could be a result of a somatic mutation. Similarly, a 60-year-old smoker developing lung cancer (Case D) can also be a result of a somatic mutation, as the mutation could have taken place in any of the lung cells during the person's lifetime.

Evaluate Remaining Cases

For Case C, where an apple tree produces its apples 2 weeks earlier than the other trees, it is not particularly clear that it's the result of a somatic mutation as this could be due to a variety of factors, not necessarily a genetic mutation in the tree.

Select the Most Likely Case

Out of Cases A and D that were identified with potential somatic mutations, the most likely case is D, where a 60-year-old smoker develops lung cancer. This mutation likely occurred in the lung cells due to exposure to carcinogens found in cigarette smoke and remained localized in the lung. On the other hand, the white patch in the purple flower (Case A) can also occur due to environmental factors and is not as convincing as the lung cancer case.

Key concepts

Germline Mutation

Germline mutations are genetic changes that occur in the reproductive cells of an organism—such as sperm or eggs—and can be passed down to offspring. This is in contrast to somatic mutations, which occur in non-reproductive cells and cannot be inherited.

For instance, in case B from the exercise, the occurrence of albinism in one child of a family suggests a germline mutation, as albinism is a heritable condition caused by mutations in genes responsible for melanin production. This mutation would have occurred in the parental gametes, making it possible for the child to inherit the condition.

Understanding germline mutations is crucial for comprehending hereditary diseases and conditions. These mutations play a central role in the study of genetics, including genetic counseling and testing, where individuals can ascertain their risk of passing specific genetic conditions to their children.

Genetic Mutation

A genetic mutation is a change to the sequence of nucleotides in DNA. Mutations can occur in various forms, such as insertions, deletions, or substitutions of DNA bases. While most mutations are neutral and do not affect the organism, others can lead to significant changes in an organism's traits or even cause diseases.

As seen in the textbook example with the purple flower and the white patch (Case A), such a mutation can result in a change of color in a specific area, likely due to a mutation affecting pigment production in those cells.

Mutations can be beneficial, harmful, or neutral, and they contribute to the genetic diversity within a population. They can be induced by external factors like radiation, chemical exposure, and smoking, or can occur spontaneously during DNA replication.

Inheritance in Genetics

Inheritance in genetics refers to the process by which genetic information is passed from parents to their offspring through their genes. The basic unit of inheritance is a gene, a sequence of DNA that encodes for a specific protein.

There are different patterns of inheritance, including dominant, recessive, co-dominant, and sex-linked traits. In the context of the exercise, understanding inheritance is essential when considering whether a trait is likely the result of a somatic or germline mutation.

Inheritance patterns determine the probability of an offspring inheriting a particular trait, such as the child with albinism (Case B), and rely on the Mendelian principles of segregation and independent assortment during gamete formation. Knowledge of genetic inheritance is vital for predicting the likelihood of an individual exhibiting certain genetic traits or acquiring genetic diseases.