Question 1

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.

Accepted Answer

If an X-carrying sperm fertilizes an egg, which already carries an X chromosome, the resulting zygote will have two X chromosomes (XX), leading to a female offspring.

Question 2

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.

Accepted Answer

An individual who is homozygous dominant for a trait would have two dominant alleles for the gene controlling the trait. In this case, both alleles would be represented by capital letters. Therefore, the correct representation for a homozygous dominant individual would be AA.

Question 3

Joe and Jane desperately want to have children,and although they have tried for two years,they have not been successful.Finally,they both agree to consult a specialist,and it turns out that Joe suffers from oligospermia (a low sperm count).He doesn't understand why this would interfere with his ability to have children since he remembers from biology class that "it only takes one sperm to fertilize an egg." What should the specialist tell him?

Accepted Answer

The answer of Joe and Jane desperately want to have...

Question 4

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.

Accepted Answer

Polygenic inheritance refers to the inheritance of a trait that is controlled by multiple genes. These genes can be located on different chromosomes and each gene might have different variations (alleles) that can contribute to the final phenotype. Examples of polygenic traits include height, skin color, and eye color.

Question 5

Regarding X-linked traits,if a father with normal color vision has children with a heterozygous mother,what percentage of the daughters will have normal color vision?
A) 0%
B) 25%
C) 50%
D) 75%
E) 100%

Accepted Answer

Since the father has normal color vision, he will pass his X chromosome with the normal vision allele to all of his daughters. The mother, being heterozygous, has one normal vision allele and one color blindness allele. Regardless of which allele the mother passes on, the presence of the father's normal allele ensures that all daughters will have at least one normal vision allele, making them have normal color vision.

Question 6

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

Accepted Answer

Turner's syndrome is caused by the absence of one X chromosome in females, resulting in a total of 45 chromosomes instead of the typical 46. Individuals with Turner's syndrome have only one sex chromosome, and it is an X chromosome, which can lead to a variety of physical and developmental abnormalities.

Question 7

If the parents are AA and aa,the offspring are all expected to be
A) sterile.
B) Aa.
C) AA.
D) aa.
E) either AA or aa.

Accepted Answer

When the parents are AA and aa, each parent contributes one of their alleles to their offspring. Therefore, all of the offspring will receive one A allele from the AA parent and one a allele from the aa parent. Thus, all the offspring will be Aa.

Question 8

Which of the following is an autosomal dominant inherited disorder?
A) Huntington's disease
B) sickle cell anemia
C) Duchenne muscular dystrophy
D) color blindness
E) deafness

Accepted Answer

Huntington's disease is an example of an autosomal dominant inherited disorder, which means that only one copy of the mutated gene is needed to inherit the disorder. Sickle cell anemia, Duchenne muscular dystrophy, color blindness, and deafness are all examples of different types of genetic disorders, but they are not inherited in an autosomal dominant manner.

Question 9

Genes that appear on the X chromosome are said to be
A) X-linked.
B) autosomal recessive.
C) heterozygous.
D) homologous.
E) lethal.

Accepted Answer

Genes that appear on the X chromosome are called X-linked genes.

Question 10

Regarding Fragile-X syndrome,
A) the affected females have nonfunctional ovaries, and estrogen production occurs at negligible levels.
B) the cause is trisomy, a mistake that occurs in meiosis, and affected individuals carry an extra chromosome.
C) the phenotype is male, but the testes fail to mature so the individuals are sterile, and the breasts are slightly enlarged.
D) the cause is a kind of chromosomal deletion known as monosomy where the phenotype is normal female.
E) the affected individuals display mental retardation, abnormal facial development, and enlarged testes in affected males.

Accepted Answer

Fragile-X syndrome is caused by a mutated gene on the X chromosome, which results in intellectual disability, abnormal facial development, and enlarged testes in affected males. Females can also be affected, but their symptoms are typically less severe due to the presence of a second, unaffected X chromosome.

Question 11

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.

Accepted Answer

Trisomy 21, also known as Down syndrome, is the most common viable chromosome abnormality, occurring in approximately 1 in 800 live births. It is characterized by an extra copy of chromosome 21, resulting in developmental delays, intellectual disability, and physical abnormalities.

Question 12

When the alleles of a gene are both expressed equally,the alleles show a form of inheritance called
A) codominance.
B) polygenic inheritance.
C) recessive inheritance.
D) sex linkage.
E) heterozygosity.

Accepted Answer

When the alleles of a gene are both expressed equally, it is known as codominance.

Question 13

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.

Accepted Answer

In simple inheritance, phenotypic characteristics are determined by a single pair of alleles. This means that there are only two options for each trait, such as dominant or recessive, and these options are determined by the interaction of the two alleles.

Question 14

The human genome consists of approximately 3.2 billion base pairs.Protein-coding genes represent ________ of the total genome.
A) 25
B) 10
C) 2
D) 50
E) 99

Accepted Answer

Protein-coding genes represent only about 2% of the total human genome, with the vast majority being non-coding DNA.

Question 15

A(n)________ allele will always be expressed regardless of what the other allele happens to be.
A) heterozygous
B) sex-linked
C) recessive
D) dominant
E) autosomal

Accepted Answer

A dominant allele will always be expressed in the phenotype of an organism, regardless of whether the second allele at that locus is dominant or recessive.

Question 16

What must be present for albinism to occur?
A) heterozygosity
B) two dominant alleles
C) sex-linked alleles
D) two recessive alleles
E) polygenic alleles

Accepted Answer

Albinism is a recessive genetic disorder, therefore two copies of the recessive allele must be present in order for albinism to occur.

Question 17

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

Accepted Answer

Klinefelter's syndrome is characterized by an additional X chromosome, resulting in a sex chromosome pattern of XXY, and individuals with this syndrome are typically male. Down's syndrome (A) is caused by an extra copy of chromosome 21. Fragile-X syndrome (C) is a genetic disorder caused by a mutation in the FMR1 gene on the X chromosome. Trisomy 21 (D) refers to Down's syndrome. Turner's syndrome (E) is a genetic disorder in which an individual has only one X chromosome (X0) and is typically female.

Quiz 20: Development and Inheritance

If an X-carrying sperm fertilizes an egg,the resulting zygote will be

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

In polygenic inheritance,

Regarding X-linked traits,if a father with normal color vision has children with a heterozygous mother,what percentage of the daughters will have normal color vision?

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

If the parents are AA and aa,the offspring are all expected to be

Which of the following is an autosomal dominant inherited disorder?

Genes that appear on the X chromosome are said to be

Regarding Fragile-X syndrome,

The most common viable chromosome abnormality is

When the alleles of a gene are both expressed equally,the alleles show a form of inheritance called

In simple inheritance,

The human genome consists of approximately 3.2 billion base pairs.Protein-coding genes represent ________ of the total genome.

A(n) ________ allele will always be expressed regardless of what the other allele happens to be.

What must be present for albinism to occur?

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