DC BIO Unit 4 Chapter 9 Quiz

In pea plants, the trait for tall stems is dominant over the trait for short stems. If two heterozygous tall plants are crossed, what percentage of the offspring would be expected to have the same phenotype as the parents?

• 100%
• 75%
• 50%
• 25%

One of the parents of a child has phenylketonuria (PKU), which is caused by recessive alleles. The other parent does not have the PKU alleles. What is the chance that the couple will have a child with phenylketonuria?

• 0%
• 50%
• 75%
• 100%

The observable traits of an organism are known as its

• allele
• dominance
• phenotype
• genotype

Each parent contributes one of the genes for a particular trait. The genes of the pair are called:

• variables
• gametes
• hybrids
• alleles

Chromosomes that carry genes that code for the same products, such as hemoglobin or eye pigment, are said to be:

• homologous
• heterozygous
• heterogeneous
• homozygous

In snapdragons, Tallness (T) is dominant to dwarfness (t). In a cross between two plants that are heterozygous for this trait, the percent of offspring expected to exhibit dwarfness is

•  25%
• 100%
• 50%
• 0%

In snapdragons, Tallness (T) is dominant to dwarfness (t). In a cross between two plants that are homozygous for the recessive allele, the percent of offspring expected to exhibit tallness is

•  25%
•  75%
• 100%
• 0%

The color black is dominant in guinea pigs. The phenotypes of homozygous black guinea pigs and heterozygous black guinea pigs are:

• black
• gray
• BB and Bb
• white

Cystic Fibrosis (CF) is a genetic disorder that is controlled by a recessive allele. If a person suffering from CF were to marry an individual who is heterozygous for the trait, what % of their children could be expected to unaffected carriers of the trait? Ignore issues of sterility in persons with CF.

• 0%
• 25%
• 75%
• 50%

Tay Sachs disease is a fatal genetic disorder. Children born with this disorder generally die before they are five years old. A couple has had three children who died of Tay Sachs. About this couple it can safely be assumed that:

•  any children they have in the future will also die from this disease
• they are both heterozygous for the Tay Sachs trait
•  they are both homozygous for the Tay Sachs trait
• one is heterozygous and the other is homozygous for the Tay Sachs trait