A female infant is born with several hundred oocytes, each one genetically unique. This is due to ______.

independent assortment and random crossover

If we are to consider the variation resulting only from independent assortment and random fertilization, any resulting offspring represents about one out of ______.

72 trillion zygotes possible

The number of gamete types from independent assortment of the homologues during meiosis in humans would be:

223 (78 million)

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

phenotypic

Recessive genes are usually expressed in humans only when _______.

both alleles are exactly the same, or homozygous

Dominant alleles are so called because under most circumstances they ______.

suppress the expression of other alleles

Two alleles expressing exactly the same information for a trait are designated as _______.

homozygous

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

Drugs and nutrition can alter normal gene expression

Mitosis differs from meiosis because in meiosis we observe _____.

tetrads

An example of multiple allele inheritance is ___________.

the ABO blood group

The reason recessive genetic disorders are more frequent than disorders inherited as dominant is that _____________.

carriers may pass them on to their offspring, unaware that they are carriers

The gene responsible for the condition known as sickle-cell anemia demonstrates _______________.

incomplete dominance

Sex chromosomes of a normal male are _______.

XY

A chromosomal aberration in which part of a chromosome is lost is known as ______________.

deletion

Inheritance of stature (height) in humans is probably due to ______.

polygene inheritance

A woman has blond hair and brown eyes. This statement is best described as indicating ___________________.

phenotype

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

incomplete dominance

Huntington's disease is an example of a(n) ___________ gene.

delayed-action

___________ is the most common type of fetal testing.

Amniocentesis

Huntington's disease involves ________.

degeneration of the basal nuclei of the brain

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

The diploid genome contains chromosomes from ___________.

both the mother and father, but only about half of the genome from each

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

sex-linked inheritance

A couple whose blood types are A (IAi) and B (IBi) may have a child with which of the following blood types?

A, B, AB, and O

Gene mutations in the sex chromosomes of the human would tend to become visibly expressed ____________.

more frequently in males

One possible scientific explanation for siblings having very different skin color is _____________.

polygene inheritance, which results in continuous phenotypic variation between extremes

Which of the following statements is true concerning screening?

Screening can be done before conception by carrier recognition or during fetal testing.

Select the incorrect statement about Chromosomes and genes.

Genes on neighboring but different chromosomes are called linked.