Chapter 29

Situation in which an individual has different alleles making up the genotype for a particular trait.

Heterozygous

Given the information in the figure, what would be the genotype of the offspring designated by the blank square?

gg

Which of the following exemplifies polygenic inheritance?

height

An individual who is heterozygous for a particular trait, yet expresses both alleles of that trait, is an example of ________.

incomplete dominance

Sex chromosomes of a normal male are ________.

XY

A dominant allele is best defined as ________.

an allele that stops or hides the expression of the other allele

Recessive genes are usually expressed in humans only when ________

both alleles are exactly the same, or homozygous

How many alleles exist for a given gene?

each gene can have a different number of alleles

Most genetic disorders are inherited through dominant genes.

false

Which of the following terms applies to a continuous phenotypic variation between two extremes?

polygenic inheritance

Amy's hand was exposed to X rays. A gene in a skin cell of her hand mutated. This mutant gene will ________.

replicate itself when the cell divides but will not be passed on to Amy's offspring

During metaphase of meiosis I, homologous chromosomes and the alleles they possess are distributed to different gametes. What is this called?

segregation

The main way a recessive allele would be expressed even when only one copy is present would be ________.

sex-linked inheritance

Which of the following is an example of a disorder that exhibits incomplete dominance?

sickle-cell anemia

Using the information provided in this figure, what is the genotype of a homozygous recessive offspring?

tt

The dominant gene is expressed when present; the recessive gene is expressed only in the absence of the dominant gene.

Dominant-recessive inheritance

Which of the following is true concerning environmental influence on genetic expression?

Drugs and nutrition can alter normal gene expression.

Inheritance of the ABO blood group type is an example of this type of inheritance.

Multiple-allele inheritance

Genes not expressed unless they are present in homozygous condition.

Recessive

Huntington's disease involves ________.

degeneration of the basal nuclei of the brain

An allele that can mask another allele is said to be __________.

dominant

The genetic determination of blood type is based on __________ inheritance.

multiple-allele

Those characteristics that can be determined on superficial inspection of an individual are known as ________.

phenotypic

Given the information in the figure, what would the genotype ratio be for the offspring?

1:2:1

Using the information provided in this figure, what is the probability of producing a homozygous dominant offspring?

25%

If two parents are heterozygous (Tt) for a trait, which of the following is NOT a possibility for their offspring?

All of their offspring would be dominant for the trait.

Genes for the same trait that have different expressions.

Allele

Which statement is most correct?

Alleles are variations of the same gene.

Chromosomes regulating most body characteristics.

Autosomes

The gene allele that suppresses or masks the expression of the other allele.

Dominant

Select the statement that best describes the difference between a gene and an allele.

Genes express a specific trait while alleles are variations of a particular gene that result in the variation we see in a genetic individual trait.

Actual genetic makeup

Genotype

Situation in which an individual has identical alleles for a particular trait.

Homozygous

The heterozygote has a phenotype intermediate between those of the homozygous dominant and homozygous recessive.

Incomplete dominance

Inheritance that results in continuous or qualitative phenotypic variations between two extremes; an example is skin color.

Polygenic inheritance

A chromosome pair that may be very different in size.

Sex chromosomes

Inherited traits determined by genes on the X or Y chromosomes.

Sex-linked inheritance

Genes on the same chromosome are said to be __________.

linked

Steven has the dominant tongue rolling phenotype but he does not know his genotype. His wife has the recessive non-tongue rolling trait. If their son can roll his tongue this means ________.

that it is impossible to tell Steven's genotype from this information alone

If a person is homozygous for a particular trait this means ________.

the person has two identical alleles for the gene responsible for the trait