Chapter 14 Test

Which term describes an organism with two identical alleles for the same gene?

Homozygous

Which of the following statements is true for organisms that are homozygous for a trait?

The organisms have an identical pair of alleles for a trait

In Mendel's experiments with pea plants, the allele for tall pea plants was dominant and the allele for short pea plants was recessive. When did Mendel see short pea plants?

When the dominant alllele for tall plants was not present

Sickle cell disease occurs when the body produces abnormal hemoglobin. This is caused by

a sequence change in a single gene

Blood type is determined by a gene with three alleles, IA, IB, and i. Because the IA and IB alleles are both dominant this trait is governed by

codominance and multiple alleles

Phenotype describes an orgainsm's physical characteristics while the genotype identifies an organism's

genetic makeup

Organisms that have two different alleles for the same gene are

heterozygous

The genetic disease cystic fibrosis involves the deletion of one amino acid from the protein CFTR. Without the amino acid, CFTR cannot function because it

is folded differently from normal CFTR

Specific substances that cut even the largest DNA molecule into fragments are called

restriction enzymes

Gel electrophoresis, a tool used by scientists to read the base sequences in DNA, separates DNA fragments based on

the length of the fragments

Red-green colorblindness in humans is a sex-linked trait. Normal color vision is determined by a dominant allele (C) and colorblindness by a recessive allele (c). Using the above Punnett square, what is the probability that the parents shown will have a colorblind daughter?

0

A student who did not have a widow's peak hairline drew this pedigree to show inheritance of the trait through three generations of her family. The pedigree can be used to determine the pattern of inheritance for this trait. As an adult, she had children with a man who also did not have a widow's peak. What percentage of their children were likely to have a widow's peak?

0%

What is the probability that a cross between a plant that is heterozygous for purple flowers (Pp) with a flower that is homozygous recessive for white flowers (pp) will produce a plant with white flowers?

50%

What type of information makes a pedigree different from a family tree?

A pedigree shows the presence of a specific trait within a family

A black (Bb) rabbit and a white (bb) rabbit are crossed. The result is 3 offspring with black fur and 1 with white. Which color fur is dominant?

Black

Human blood has an Rh factor, which can be either Rh+ or Rh−. The Rh+ allele is dominant; the Rh− allele is recessive. In an investigation, individuals tested their blood types. The results are shown in the table. What would be a valid conclusion that could be included in the lab report, based on the information in this table?

Individuals C and D both have two Rh− alleles

The table shows the combinations of alleles that result in human ABO blood types. A biology student explains that two parents with type AB blood can produce children with any one of the four possible human blood types. Is the student's explanation correct?

No, the parents cannot produce children with type O blood

In pea plants, the allele for round seed shape (R) is dominant over the allele for wrinkled seed shape (r). The allele for yellow seeds (Y) is dominant over the allele for green seeds (y). The Punnett square shows a cross between two parent pea plants. What is the genotype of the male parent pea plant represented in the top row of the Punnett square?

RrYy

The diagram shows the human pedigree of free and attached earlobes in four generations of one family. A shaded area represents free earlobes, and a white area represents attached earlobes. The trait for free earlobes is dominant. What is true of individual 2 in the pedigree?

She is homozygous for the trait

Restriction enzymes are an important tool used by scientists to manipulate DNA and study genomes. The sequences recognized by several restriction enzymes are shown in the diagram. How are all of the restriction enzymes shown in the diagram similar?

They all cut DNA only at specific sequences

Cystic fibrosis is a genetic disorder caused by a recessive allele. The table shows how possible genotypes for this trait affect individuals. Two parents, each with one normal allele and one allele for cystic fibrosis, have children. Which list most completely represents the phenotypes of the children this couple could possibly have?

affected, carrier, and unaffected