Question

1.You are studying a familial breast cancer gene. All previous pedigree data indicate that this type of cancer is inherited as autosomal dominant trait. Still, in some instances the cancer skips a generation. If this breast cancer is autosomal dominant, what is a likely explanation as to why it skipped a generation sometimes?

a. Skipping generations is common in autosomal dominant traits. b. This breast cancer is not 100% penetrant. c. Only the environment can cause cancer. d. No reasoning could explain this. Cancer cannot be autosomal dominant.

2.

To study the genetic components of attention deficit (hyperactivity) disorder, physicians looked at data of adopted children and compared the biological and adoptive parents. In most cases, the adoptive parents did not have hyperactivity, but the biological parents did. This indicates

1. a genetic component.
2. an environmental component.
3. an equal contribution of genetics and environment.
4. No conclusions can be made.

Answer 1

1)b)This breast cancer is not 100% penetrant.

However, the risk associated with many of these genes is not well understood. Most are termed "moderate- or low-penetrant" genes which means that, on their own, they would be expected to have a relatively small effect on breast cancer risk. However, in combination with other genes and/or environmental factors, these genes may lead to a significant risk of breast cancer.

2) a) a genetic component. Adopted parents did not have hyperactivity, but biological parents have this means it is hereditary and inherite parents to their offsprings.