Bio 003 Chapter 9

A couple has two female children. What is the probability that their next child will be male? A) 50% B) 33% C) 25% D) 67% E) 100%

A) 50%

The phenotypic ratio resulting from a dihybrid cross showing independent assortment is expected to be A) 9:3:3:1. B) 3:1. C) 3:9:9:1. D) 9:1:1:3. E) 1:2:1.

A) 9:3:3:1.

Mendel's law of independent assortment states that A) each pair of alleles segregates independently of the other pairs of alleles during gamete formation. B) chromosomes sort independently of each other during mitosis and meiosis. C) genes sort independently of each other in animals but not in plants. D) independent sorting of genes produces polyploid plants under some circumstances. E) None of the choices are correct.

A) each pair of alleles segregates independently of the other pairs of alleles during gamete formation.

Mendel's law of segregation indicates that A) gametes have one allele copy for each gene. B) more gametes carrying the dominant allele are produced than gametes carrying the recessive allele. C) two alleles segregate into each gamete. D) gametes are diploid. E) All of the choices are correct.

A) gametes have one allele copy for each gene.

All the offspring of a cross between a red-flowered plant and a white-flowered plant have pink flowers. This means that the allele for red flowers is __________ to the allele for white flowers. A) incompletely dominant B) dominant C) recessive D) codominant E) pleiotropic

A) incompletely dominant

Many human traits, such as our performance on intelligence tests or our susceptibility to heart disease, are ________. A) influenced by both genes and the environment B) determined by genes in some people and by the environment in other people C) determined only by our genes D) determined solely by environmental factors E) All of the choices are correct.

A) influenced by both genes and the environment

Any gene located on a sex chromosome A) is called a sex-linked gene. B) will exhibit codominance. C) will exhibit pleiotropy. D) is called a dominant allele. E) is called a recessive gene.

A) is called a sex-linked gene.

Amniocentesis and chorionic villus sampling allow for __________ and __________ of the fetus so that it can be tested for abnormalities. A) karyotyping . . . biochemical testing B) imaging . . . karyotyping C) direct observation . . . biochemical testing D) imaging . . . biochemical testing E) sexing . . . imaging

A) karyotyping . . . biochemical testing

What is the specific location of a gene on a chromosome? A) locus B) allele C) genotype D) phenotype E) genetic disorder

A) locus

How many sex chromosomes are in a human gamete? A) one B) five C) four D) two E) three

A) one

What is the normal complement of sex chromosomes in a human male? A) one X chromosome and one Y chromosome B) one Y chromosome C) two Y chromosomes D) two X chromosomes E) two X chromosomes and one Y chromosome

A) one X chromosome and one Y chromosome

What would you examine to determine whether a trait is sex linked? A) pedigree B) DNA sequence C) blood test D) karyotype E) All of the choices are correct.

A) pedigree

Many genetic disorders of humans are caused by A) recessive alleles. B) drinking during pregnancy. C) a mutation that occurs in the egg, sperm, or zygote that gives rise to the affected individual. D) multiple alleles. E) None of the choices are correct.

A) recessive alleles.

Why not use ultrasound instead of amniocentesis for prenatal diagnosis? Isn't it safer? Explain.

An ultrasound is not used instead of amniocentesis for prenatal diagnosis because it is only an image and does not demonstrate any information on genetics.

A couple has two female children. What is the probability that their next child will be male? A) 33% B) 50% C) 75% D) 25% E) 67%

B) 50%

What is a testcross? A) a mating between an individual of unknown genotype and an individual heterozygous for the trait of interest B) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest C) a mating between two individuals heterozygous for the trait of interest D) a mating between an individual of unknown genotype and an individual homozygous dominant for the trait of interest E) None of the choices are correct.

B) a mating between an individual of unknown genotype and an individual homozygous recessive for the trait of interest

Alleles are described as ________. A) alternate phenotypes B) alternate versions of a gene C) homologous chromosomes D) environmental factors that affect gene expression E) None of the choices are correct.

B) alternate versions of a gene

This hypothetical pedigree for a disease in humans illustrates inheritance that is (image) A) autosomal dominant B) autosomal recessive C) carried on the Y chromosome D) sex-linked dominant E) None of the choices are correct.

B) autosomal recessive

For most sexually reproducing organisms, Mendel's laws A) indicate if a particular genotype will cause a certain phenotype. B) cannot strictly account for most patterns of inheritance. C) explain the reasons why certain genes are dominant. D) help us understand the global geographic patterns of genetic disease. E) None of the choices are correct.

B) cannot strictly account for most patterns of inheritance.

An individual who is homozygous ________. A) expresses the dominant trait B) carries two different alleles for a gene C) expresses the recessive trait D) carries two copies of the same allele for a gene E) All of the choices are correct.

B) carries two different alleles for a gene

The expression of both alleles for a trait in a heterozygous individual illustrates A) blending inheritance. B) codominance. C) incomplete dominance. D) pleiotropy. E) polygenic inheritance.

B) codominance.

The mechanism that "breaks" the linkage between linked genes is A) codominance. B) crossing-over. C) pleiotropy. D) incomplete dominance. E) independent assortment.

B) crossing-over.

Individual features of all organisms are the result of A) the environment. B) genetics and the environment. C) the environment and individual needs. D) genetics and cytoplasmic determinants. E) genetics.

B) genetics and the environment.

Mendel conducted his most memorable experiments on A) guinea pigs. B) peas. C) clones. D) roses. E) fruit flies

B) peas.

Which of the following terms refers to the situation where a single phenotypic characteristic is determined by the additive effects of two or more genes? A) incomplete dominance B) polygenic inheritance C) pleiotropy D) codominance E) blending inheritance

B) polygenic inheritance

An individual with the blood group genotype IAIB has the phenotype AB. What is the relationship between the IA and IB alleles? A) pleiotropy B) IA is dominant C) codominance D) incomplete dominance E) IB is dominant

C) codominance

Which trait is polygenic in humans? A) blood type B) sickle-cell disease C) height D) cystic fibrosis E) None of the choices are correct.

C) height

A mating between a true-breeding purple-flowered pea plant and a true-breeding white-flowered pea plant would produce a(n) ______. A) true-breeding variety B) inbred organism C) hybrid D) P generation E) F2 generation

C) hybrid

Linked genes are usually ________. A) codominant B) found on the X chromosome C) located close together on a chromosome D) found on the Y chromosome E) different loci on heterologous

C) located close together on a chromosome

The vast majority of people afflicted with recessive disorders are born to parents who were A) slightly affected by the disease, showing some but not all of the symptoms. B) subjected to some environmental toxin that caused the disease in their children. C) not affected at all by the disease. D) both affected by the disease. E) None of the choices are correct

C) not affected at all by the disease.

The best definition of a true-breeding plant is one that ______. A) produces sterile offspring when cross-fertilized B) self-fertilizes to produce hybrid offspring C) self-fertilizes to produce offspring identical to the parent D) cannot be cross-fertilized E) becomes sterile after three generations

C) self-fertilizes to produce offspring identical to the parent

Achondroplasia is a form of dwarfism caused by a dominant allele. The homozygous dominant genotype causes death, so individuals who have this condition are all heterozygotes. If a person with achondroplasia mates with a person who does not have achondroplasia, what percentage of their children would be expected to have achondroplasia? A) 75% B) 100% C) 0% D) 50% E) None of the choices are correct.

D) 50%

Which of the following is/are recessive sex-linked human conditions? A) muscular dystrophy B) red-green color blindness C) hemophilia D) All of the choices are correct. E) None of the choices are correct.

D) All of the choices are correct.

Why are sex-linked conditions more common in men than in women? A) Men acquire two copies of the defective gene during fertilization. B) Women simply do not develop the disease regardless of their genetic composition. C) The sex chromosomes are more active in men than in women. D) Men need to inherit only one copy of the recessive allele for the condition to be fully expressed. E) None of the choices are correct.

D) Men need to inherit only one copy of the recessive allele for the condition to be fully expressed.

Which of the following techniques is used to collect fetal cells during pregnancy for genetic testing? A) monohybrid cross B) testcross C) dihybrid cross D) amniocentesis E) pedigree analysis

D) amniocentesis

A mating between a purebred purple-flowered pea plant and a purebred white-flowered pea plant would produce a(n) ________. A) P generation B) purebred variety C) F2 generation D) hybrid E) karyotype

D) hybrid

The ________ is most commonly found in nature. A) recessive trait B) dominant trait C) parental type D) wild-type trait E) All of the choices are correct.

D) wild-type trait

Chromosomes that are not sex chromosomes are called ______. A) dominant B) nonsexosomes C) centrosomes D) allosomes E) autosomes

E) autosomes

Sickle-cell disease represents A) multiple alleles, pleiotropy, and blended inheritance. B) codominance and blended inheritance. C) codominance and multiple alleles. D) multiple alleles and pleiotropy. E) codominance and pleiotropy

E) codominance and pleiotropy

Mendel crossed true-breeding purple-flowered plants with true-breeding white-flowered plants, and all of the resulting offspring produced purple flowers. The allele for purple flowers is ______. A) monohybrid B) recessive C) independent D) segregated E) dominant

E) dominant

Genes located close together on the same chromosomes are referred to as __________ genes and generally __________. A) associated . . . sort independently during meiosis B) homologous . . . are inherited together C) codependent . . . do not sort independently during meiosis D) linked . . . sort independently during meiosis E) linked . . . do not sort independently during meiosis

E) linked . . . do not sort independently during meiosis

In humans, normal skin pigmentation is influenced by a dominant gene (A), which allows pigmentation to develop. All individuals who are homozygous for the recessive allele (a) are unable to produce an enzyme needed for melanin formation and are therefore referred to as albino. Two normal parents produce an albino child. What are the chances that the next child will be an albino?

normal skin x albino AA aa Aa normal skin x normal skin Aa As normal skin: 1 AA, 2 Aa albino: 1 aa The chances that the next child will be an albino are 25%