The Punnett-square method is used to predict _____.
probable outcomes of genetic crosses
Which of the following observations suggested that blending was, at best, an incomplete explanation for inheritance?
a. a mating between a white and black horse rarely produced gray offspring
b. parents without freckles have children with freckles
c. a cross between white-flowered and purple-flowered peas never produced lavender-flowered offspring
d. all of the choices are correct
Diploid organisms are so described because _____.
each gene is paired with another located at the same locus on a homologous chromosome
Which of the following observations supports the suggestion that the environment contributes to the phenotypic variability of a population?
a. the blooms of a hydrangea will be pink if the soil is acidic, and blue if alkaline
b. clones of yarrow plants grow differently at different elevations
c. cooling the skin of Himalayan rabbits changes the fur color from white to black
d. all of the choices
A test cross can be performed to determine if _____.
an F1 or F2 individual with a phenotypically dominant trait is homozygous or heterozygous
Crossing a heterozygous parent with a homozygous recessive parent should produce a ratio of dominant-to-recessive phenotypes of approximately _____.
When plotted graphically, continuously variable features such as height appear _____.
as bell curves
Dihybrid crosses provided the information used to formulate the theory of _____.
Biologists use the term segregation to describe _____.
how gene pairs separate during meiosis and end up in different gametes
During crossing over, _____.
corresponding portions of genetic material are switched between homologous chromosomes
What best explains the variation in the coat color of Labrador retrievers?
proteins produced by a variety of genes at different loci interact to determine pigment intensity and deposition
An individual described as heterozygous has a _____.
pair of nonidentical alleles
In codominance, _____.
pairs of nonidentical alleles affecting two phenotypes are both expressed in heterozygotes
In Marfan syndrome, a relatively common genetic disease, _____.
the synthesis of a connective tissue protein is altered, affecting the smooth muscle within the aorta
In the first stage of a monohybrid experiment, two _____ are crossed.
homozygous parents differing in a trait controlled by one gene
The pea plant was a good selection for Mendel's experiments because _____.
pea plants readily self-fertilize and cross-fertilize
Humans have 23 pairs of chromosomes; how many linkage groups are present in humans?
twenty-three - one group for each pair of chromosomes
An allele is considered dominant when _____.
its effects mask those of the allele paired with it
Some populations display continuous variation, which arises when _____.
multiple genes influence the inheritance of the same trait
In humans, typical cells are _____, while gametes are _____.