Exam 4: Pedigree Analysis in Human Genetics

A large family exhibits a previously undiscovered trait: green hair. One parent has the trait as do 6 of their 12 children (50%). (a) Satisfy yourself that this result could be produced by either one of two situations: Green hair is caused by a dominant allele, and the green-haired parent has one copy of that allele; OR green hair is a recessive trait; the green-haired parent is homozygous and the other parent is heterozygous. (b) How might we determine which one of these possibilities is true?

In autosomal dominant inheritance

What are the chances that a woman who is color blind will have a son who is color blind?

When affected males produce all affected daughters and no affected sons, the genetic disease is likely to be ____________________.

Tomas has a rare genetic defect that causes him to snore excessively. Tomas's partner, Glora, does not have this problem. Tomas's sister, Eloise, also does not have this problem. Eloise has a daughter who is normal and identical twin boys who snore excessively like Tomas. The parents of Tomas, Eloise, and Gloria are all normal. Draw a pedigree for this family. What is the mode of transmission of this defect?

If a trait is inherited in an autosomal recessive fashion, which of the following is not true?

Y-linked traits are

A color-blind man has a son who is also color blind. The son inherited the condition from his ____________________.

In pedigree analysis, is it always possible to determine the mode of inheritance for a trait? What factors can complicate this task?

Almost all cases of alkaptonuria, a rare genetic disorder, arise as the result of mating between two unaffected parents. Why?

The basic method of genetic analysis in humans requires a ____________________ of several generations.

The most common forms of color blindness cause inability to properly perceive the colors ____________________ and ____________________.

The degree to which a trait is expressed in individuals is the ____________________ of the trait.

Compared to experimental organisms such as the garden pea, why is it that humans are poor subjects for genetic investigations?

If a man expresses an X-linked recessive trait, we can draw the following conclusion:

Autosomal dominant traits are inherited from affected parents.

Huntington's disease, a severe autosomal dominant neurological disorder, shows a ____________________ in its expression.

Variation in expressivity and penetrance of genes is due to the effects of other genes and the environment.

If a man and his wife are both homozygous for a disease-causing recessive gene, then ____________________ of their children will be affected.

Explain the inheritance of mitochondrial DNA and how a person inherits a mitochondrial genetic disease.