71) ________ percent of human nucleotide bases are the same in all people.

A) 2

B) 27

C) 58

D) 72

E) 99

72) Genes that appear on the X chromosome are said to be ________.

A) X-linked

B) autosomal recessive

C) heterozygous

D) homologous

E) lethal

73) The most common viable chromosome abnormality is ________.

A) Fragile-X syndrome

B) Trisomy 21

C) Turner’s syndrome

D) Klinefelter’s syndrome

E) a translocation defect

74) Individuals with ________ have only one sex chromosome, and it is an X chromosome.

A) Trisomy 21

B) Down’s syndrome

C) Turner’s syndrome

D) Fragile-X syndrome

E) Klinefelter’s syndrome

75) In which of the following does the individual carry the sex chromosome pattern XXY and is a male?

A) Down’s syndrome

B) Klinefelter’s syndrome

C) Fragile-X syndrome

D) Trisomy 21

E) Turner’s syndrome

76) An individual who is homozygous dominant for a trait would be represented as

A) aA.

B) aa.

C) AA.

D) Aa.

E) a fusion of the different phenotypes of the given trait.

77) In simple inheritance,

A) phenotypic characteristics are determined by a single pair of alleles.

B) phenotypic characteristics are determined by multiple alleles.

C) phenotypic characteristics are determined by the action of two genes.

D) phenotypic characteristics are controlled by regulator genes on a chromosome other than the one that has the structural genes.

E) phenotypic characteristics are determined by the genes on the Y chromosome.

78) In polygenic inheritance,

A) phenotypic characteristics are always controlled by genes on a single chromosome.

B) phenotypic characteristics are determined by interactions among several genes.

C) phenotypic characteristics are determined by the genes on the Y chromosome.

D) phenotypic characteristics are determined by a single pair of alleles.

E) phenotypic characteristics are determined by the action of a single gene.

79) When the alleles of a gene are both expressed equally, the alleles show a mechanism of inheritance called ________.

A) codominance

B) polygenic inheritance

C) recessive inheritance

D) sex linkage

E) heterozygosity

80) If an X-carrying sperm fertilizes an egg, the resulting zygote will be ________.

A) either male or female

B) male only

C) female only

D) nonviable

E) both male and female